Dissertations / Theses on the topic 'Chemistry - complex di ruthenium'

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O complexo inédito mer-[RuCl3(dppb)H2O], foi caracterizado como precursor de uma série de compostos fosfínicos. Foram testadas sínteses do complexo título com ligantes providos de diferentes modos de coordenação, tais como os monodentados (L= DMSO, MeOH, NO e CO, py, 4-Mepy), exodentado (L= 4-CNpy), bidentados (L-L= 2,2'-bipy, fen) e ambidentado (L-L= 4,4'-bipy). Os produtos destas reações foram isolados como espécies bifosfínicas de rutênio (III) de fórmula geral mer-[RuCl3(dppb)(L)], cis-[RuCl2(dppb)(L-L)]+ e [Ru2Cl6(dppb)2(μ-4,4'-bipy)]. Reações do mer-[RuCl3(dppb)H2O] e fosfinas mono, bi e tridentadas, foram investigadas e a partir destas, obteve-se a série de complexos mono, bi e trifosfínicos de rutênio (II), conhecidos na literatura como reagentes para sínteses de compostos de rutênio, tais como [RuCl2(dppb)(PPh3)], [RuCl2(P-P)2] (P-P= dppm, dppe e dppp) e [Ru2Cl4(P-P)3] (PP= dppb), e [Ru2Cl3(P-P-P)2]Cl (P-P-P= tdpme e etp). A partir dos complexos do tipo [Ru2Cl3(P-P-P)2]Cl, obteve-se compostos do tipo [RuCl(P-P-P)(N-heterocíclico)]Cl, dando continuidade à nova série de complexos mononucleares solvato, [RuCl(P-P-P)(solvente)]Cl. Os compostos de Ru(II) e Ru(III) obtidos, foram caracterizados através de espectroscopia de absorção na região do infravermelho, ultravioleta-visível, RPE, RMN 31P, medidas de condutância molar, medidas de susceptibilidade magnética, análise elementar, voltametria cíclica e em alguns casos, difração de raios-X. O comportamento eletroquímico dos complexos bifosfínicos de Ru(III) mer- [RuCl3(dppb)H2O] e mer-[RuCl3(dppb)(L)], apresentou perfil bastante peculiar. A partir da metodologia empregada na obtenção por via eletroquímica, atribuiu-se as espécies Ru2II/III, [Ru2Cl5(dppb)2], de Ru(II), [Ru2Cl4(dppb)2], [RuCl2(dppb)(L)2] e [Ru2Cl4(dppb)2(L)], como produtos formados na superfície do eletrodo,...
The new complex mer-[RuCl3(dppb)H2O] was characterized as precursor of a series of ruthenium (III) mono and biphosphines complexes. Syntheses of the complex title were tested with ligands provided from different coordination manners, such as the monodentates ligands (L = DMSO, MeOH, NO, CO, py, 4-Mepy), exobidentate ligand (L = 4-CNpy), chelate ligands (L-L = 2,2'-bipy, fen) and umbidentate ligand (L-L = 4,4'-bipy). The reaction products were isolated as ruthenium (III) phosphines complexes of general formula mer-[RuCl3(dppb)(L)], cis-[RuCl2(dppb)(L-L)]+, and [Ru2Cl6(dppb)2(μ-4,4'-bipy)], respectively. Reactions of the mer-[RuCl3(dppb)H2O] with monophosphines, diphosphines and triphosphines were investigated and starting from these, it was obtained the series of complex mono, di and triphosphines ruthenium (II), wich are known in the literature as starting material for syntheses of compounds of ruthenium, such as [RuCl2(dppb)(PPh3)], [RuCl2(P-P)2] (P-P = dppm, dppe and dppp) and [Ru2Cl4(P-P)3] (P-P = dppb), and [Ru2Cl3(PP- P)2]Cl (P-P-P = tdpme and etp). Mononuclear ruthenium complexes of the type [RuCl(P-PP)( N-heterocylic)]Cl, were isolated from the reaction of the binuclear [Ru2Cl3(P-P-P)2]Cl (PP- P = tdpme and etp) with excess of ligand. Standard spectroscopic methods, particularly IR, UV-Vis, EPR, 31P{1H} MNR, were extensively used to characterize (sometimes in conjunction with X-ray crystallography) all of the species discussed in this thesis. The complexes were also characterized by molar conductance, magnetic moment measurement, elementary analysis and cyclic voltammetry. The electrochemical behaviour of the biphosphine complexes Ru(III) presented quite peculiar profiles. Starting from the methodology using electrochemistry route, it was attributed the species of Ru2II/III, [Ru2Cl5(dppb)2], and of Ru(II), [Ru2Cl4(dppb)2], [RuCl2(dppb)(L)2] and [Ru2Cl4(dppb)2(L)], ...(Complete abstract, click electronic access below)

Orientador: Alzir Azevedo Batista
Banca: Luiz Antônio Andrade de Oliveira
Banca: Regina Frem
Banca: Wagner Ferraresi de Giovani
Banca: Benedito Lima Neto
Resumo: O complexo inédito mer-[RuCl3(dppb)H2O], foi caracterizado como precursor de uma série de compostos fosfínicos. Foram testadas sínteses do complexo título com ligantes providos de diferentes modos de coordenação, tais como os monodentados (L= DMSO, MeOH, NO e CO, py, 4-Mepy), exodentado (L= 4-CNpy), bidentados (L-L= 2,2'-bipy, fen) e ambidentado (L-L= 4,4'-bipy). Os produtos destas reações foram isolados como espécies bifosfínicas de rutênio (III) de fórmula geral mer-[RuCl3(dppb)(L)], cis-[RuCl2(dppb)(L-L)]+ e [Ru2Cl6(dppb)2(μ-4,4'-bipy)]. Reações do mer-[RuCl3(dppb)H2O] e fosfinas mono, bi e tridentadas, foram investigadas e a partir destas, obteve-se a série de complexos mono, bi e trifosfínicos de rutênio (II), conhecidos na literatura como reagentes para sínteses de compostos de rutênio, tais como [RuCl2(dppb)(PPh3)], [RuCl2(P-P)2] (P-P= dppm, dppe e dppp) e [Ru2Cl4(P-P)3] (PP= dppb), e [Ru2Cl3(P-P-P)2]Cl (P-P-P= tdpme e etp). A partir dos complexos do tipo [Ru2Cl3(P-P-P)2]Cl, obteve-se compostos do tipo [RuCl(P-P-P)(N-heterocíclico)]Cl, dando continuidade à nova série de complexos mononucleares solvato, [RuCl(P-P-P)(solvente)]Cl. Os compostos de Ru(II) e Ru(III) obtidos, foram caracterizados através de espectroscopia de absorção na região do infravermelho, ultravioleta-visível, RPE, RMN 31P, medidas de condutância molar, medidas de susceptibilidade magnética, análise elementar, voltametria cíclica e em alguns casos, difração de raios-X. O comportamento eletroquímico dos complexos bifosfínicos de Ru(III) mer- [RuCl3(dppb)H2O] e mer-[RuCl3(dppb)(L)], apresentou perfil bastante peculiar. A partir da metodologia empregada na obtenção por via eletroquímica, atribuiu-se as espécies Ru2II/III, [Ru2Cl5(dppb)2], de Ru(II), [Ru2Cl4(dppb)2], [RuCl2(dppb)(L)2] e [Ru2Cl4(dppb)2(L)], como produtos formados na superfície do eletrodo,...(Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The new complex mer-[RuCl3(dppb)H2O] was characterized as precursor of a series of ruthenium (III) mono and biphosphines complexes. Syntheses of the complex title were tested with ligands provided from different coordination manners, such as the monodentates ligands (L = DMSO, MeOH, NO, CO, py, 4-Mepy), exobidentate ligand (L = 4-CNpy), chelate ligands (L-L = 2,2'-bipy, fen) and umbidentate ligand (L-L = 4,4'-bipy). The reaction products were isolated as ruthenium (III) phosphines complexes of general formula mer-[RuCl3(dppb)(L)], cis-[RuCl2(dppb)(L-L)]+, and [Ru2Cl6(dppb)2(μ-4,4'-bipy)], respectively. Reactions of the mer-[RuCl3(dppb)H2O] with monophosphines, diphosphines and triphosphines were investigated and starting from these, it was obtained the series of complex mono, di and triphosphines ruthenium (II), wich are known in the literature as starting material for syntheses of compounds of ruthenium, such as [RuCl2(dppb)(PPh3)], [RuCl2(P-P)2] (P-P = dppm, dppe and dppp) and [Ru2Cl4(P-P)3] (P-P = dppb), and [Ru2Cl3(PP- P)2]Cl (P-P-P = tdpme and etp). Mononuclear ruthenium complexes of the type [RuCl(P-PP)( N-heterocylic)]Cl, were isolated from the reaction of the binuclear [Ru2Cl3(P-P-P)2]Cl (PP- P = tdpme and etp) with excess of ligand. Standard spectroscopic methods, particularly IR, UV-Vis, EPR, 31P{1H} MNR, were extensively used to characterize (sometimes in conjunction with X-ray crystallography) all of the species discussed in this thesis. The complexes were also characterized by molar conductance, magnetic moment measurement, elementary analysis and cyclic voltammetry. The electrochemical behaviour of the biphosphine complexes Ru(III) presented quite peculiar profiles. Starting from the methodology using electrochemistry route, it was attributed the species of Ru2II/III, [Ru2Cl5(dppb)2], and of Ru(II), [Ru2Cl4(dppb)2], [RuCl2(dppb)(L)2] and [Ru2Cl4(dppb)2(L)], ...(Complete abstract, click electronic access below)
Doutor

The study of macrocyclic ligands for complexation of alkali metals (macrobicyclic polyether cryptands) and transition metals (tetraaza macrocycles) is reported. The synthesis of a new bis(phosphotriester) macrobicyclic polyether cryptand, O = P (O(CH$\sb2)\sb2\rm O(CH\sb2)\sb2O(CH\sb2)\sb2O\rbrack\sb3$ P = O, 1, called phosphocrypt, and its acyclic tripodal precursor O = P (O(CH$\sb2)\sb2\rm O(CH\sb2)\sb2O(CH\sb2)\sb2OH\rbrack\sb3$, 2, is described. Aqueous stability constants (K$\sb{\rm s}$) measured with a cation selective electrode with potassium and rubidium are 10$\sp{3.7}$ and 10$\sp{3.6}$ for 1, and are 10$\sp{3.6}$ and 10$\sp{3.0}$ for 2, respectively. The K$\sb{\rm s}$ values for phosphocrypt are 1000 fold greater than comparably sized nitrogen bridgehead cryptands. $\sp1$H and $\sp{13}$C NMR indicate 1 is flexible at 20$\sp\circ$C. Molecular mechanics calculations confirm the flexibility of 1. Also reported are the synthesis and characterization of (1) a new mixed-valence bimetallic ruthenium complex, Ru$\sb2\rm (C\sb{20}H\sb{36}N\sb8)Cl\sb{4}\sp{+}$, 3, that contains a cross-conjugated bridge that links two tetraaza macrocycles; and (2) the formation, physical properties, and reduction chemistry of a new iron $\beta$-diimine keto macrocyclic complex, Fe(C$\rm \sb{10}H\sb{18}N\sb{4}O)(CH\sb3CN)\sb{2}\sp{2+},$ 4. The ruthenium dimer 3 was formed by oxidative dehydrogenation of Ru(C$\rm\sb{10}H\sb{24}N\sb4)(Cl\sb2)\sp+$ and its mass was determined by positive ion fast atom bombardment mass spectrometry. The binuclear species 3 is assigned as a Robin and Day strongly coupled class III mixed-valence species based on cyclic voltammetry, electronic spectroscopy, and X-ray photoelectron spectroscopy (XPS). The XPS photopeaks of 3 for the binding energies from the Ru 3p$\sb{1/2}$ and Ru 3p$\sb{3/2}$ regions show only a single peak, indicating the unpaired electron is delocalized on the short (10$\sp{-17}$ s) timescale of the XPS experiment. The keto complex 4 was formed in high yields ($>$90%) from the reaction of Fe$\rm\sb2(C\sb{20}H\sb{36}N\sb8)(CH\sb3CN)\sb{4}\sp{4+}$, 5, (the diiron analog of 3) with molecular oxygen. Its mass was determined by electrospray mass spectrometry and its structure by NMR spectroscopy ($\sp1$H, $\sp{13}$C, COSY, NOE DIFF). The complex is rigid at room temperature in CD$\sb3$CN and this allows the assignment of the ten distinct protons. Reduction of the keto group in 4 under anaerobic conditions, followed by aerobic oxidation, leads to the reformation of 5.

Our aim was to develop the synthetic potential and reaction chemistry of Ir3+ and Ru2+ electrophiles by preparing well-characterized complexes whose properties are controllable by modification of the ancillary ligand environment Specifically, we prepared a series of ruthenium complexes to serve as selective hydrogenation and hydrogenolysis catalysts of furan derivatives. We also expanded the synthesis of electrophilic Ir3+ di-thiolate complexes. These types of compounds could eventually serve as catalysts precursors for the addition of weak nucleophiles to alkynes and nitriles.

Oligothiophenes are of increasing interest in organic based electronic devices in part due to their high electron and hole mobilities. In an organic photovoltaic (OPV) device, the electronic properties of oligothiophenes make them advantageous as charge transfer junctions. To serve as charge transfer junctions, oligothiophenes must be functionalized to bind to the donor and acceptor parts of the device. The donor and acceptor parts are different materials and the synthesis of asymmetric oligothiophenes is of great interest. Previous researchers in our lab synthesized four asymmetric oligothiophenes, two with two thiophene subunits and two with four. Each set of oligothiophenes contained a pair of constitutional isomers. Here we report the synthesis of another asymmetric oligothiophene, one with three thiophene subunits. This compound is functionalized with bipyridine to bind Ru(bpy)22+ and with phosphonic acid moieties to bind CdSe nanoparticles. The synthesis was carried out by bonding a phosphonic acid moiety to bithiophene and bipyridine to thiophene and then coupling the phosphate-bithiophene and thiophene-bipyridine. Standard Stille couplings were used for carbon-carbon bond formation. The resulting compounds have complex NMR spectra and overlapping Ru MLCT and π-π* transitions at 450 nm with molar extinction coefficient on the order of 3 x 105 M-1 cm-1. The thiophene fluorescence is quenched by Ru(bpy)22+. These optical properties compare closely with the previous compounds synthesized. Solar cells occupy significant attention in the media, politics and science for their promise of continual pollution-free energy. Quantum dots, metal complexes and organic compounds are all under research as viable replacements for expensive silicon solar cells. To test the efficacy of a light harvesting compound before constructing a solar cell, a model system is constructed to show electron transfer from the light harvester into an electron acceptor. We synthesized oligothiophenes and oligothiophene-ruthenium complexes and tested their ability to act as sensitizers and charge transfer junctions. To do this, they were bonded to CdSe nanoparticles and their optical properties were measured. Steady-state photoluminescence and time correlated single photon counting were used to observe the effects on fluorescence and fluorescence lifetime of the CdSe-oligothiophene and CdSe-oligothiophene-ruthenium complexes before and after binding. It was found that CdSe fluorescence was quenched when bound to an oligothiophene ruthenium complex, and that the fluorescence of the oligothiophene was quenched when bound to CdSe in the absence of ruthenium. The fluorescence lifetimes of the quenched species were shortened.

Thesis (MSc)--University of Stellenbosch, 2003.
ENGLISH ABSTRACT: Ruthenium, as one of the platinum group metals, was investigated to determine the aquation rate constant of [RuCl6]3- and the anation rate constant of [RuCl5(H2O)]2-. This two reactions represent the equilibrium reaction [RuCl6]3- + H2O ⇄ [RuCl5(H2O)]2- + Cl-. The reactions were followed, using stopped-flow injection and UV/Visible spectroscopy, at different temperatures. The aquation and anation rate constants were determined with good precision and thermodynamic values for the reactions were calculated. The pseudo first order aquation rate constant, k65, was determined by calculation from the regression line as k65 = 52.1 (±3.7) x10-3 s-1 at 25°C. The activation energy, Ea, is 90.1 (±1.2) kJ.mol-1 and the enthalpy and entropy of activation is 87.7 (±1.2) kJ.mol-1 and 24.7 (±4.3) J.K-1.mol-1, respectively. The aquation rate constant was found to be dependent on the hydrochloric acid concentration, decreasing with increasing hydrochloric acid concentration. From the regression line at 25°C the second order anation rate constant, k56, was calculated as 1.62 (±0.11) x10-3 M-1s-1. The activation energy is 88.0 (±1.4) kJ.mol-1, with the enthalpy and entropy of activation 85.6 (±1.4) kJ.mol-1 and –11.2 (±4.7) J.K-1.mol-1, respectively. The influence of the hydrochloric acid concentration of the solution on the anation rate constant was not investigated. The equilibrium constant for the reaction studied was calculated from the rate constants for the aquation and anation reactions. The equilibrium constant, K6, was calculated as 0.0311 M-1 at 25°C. The equilibrium constant, when compared to literature, was found to be dependent on the hydrochloric acid concentration. It was then used, in conjunction with data from the literature, to construct two distribution diagrams. Distribution diagrams for the Ru(III) aquachloro species show between 79.9% to 72.3% [RuCl6]3- present in 12M HCl. The two distribution diagrams were very similar and it is not possible to resolve the issue of a final distribution diagram for the aqua-chloro Ru(III) system without further investigation into the all the other rate constants of the Ru(III) aqua-chloro species. The rate constants and thermodynamic values for the Ru(III) reaction were compared to corresponding data (from literature) for Rh(III) and Ir(III) because several comparisons between these platinum group metals have been noted. It was found that for both the aquation and anation rate constants, the following trend was observed: Ru(III) > Rh(III) > Ir(III). These differences are in certain cases exploited in the refining of these platinum group metals. Crystals of diethylenetriamine hexachlororuthenate(III) was prepared and characterised by x-ray crystallography and CHN analysis. The average Cl-Ru bond length for the crystal was 2.371 Å. The crystal structure was compared to hexaaquaaluminium hexachlororuthenate(III) tetrahydrate and diethylenetriamine hexachlororhodate(III). The metal-chloride bond lengths of all the crystals were found to be similar (2.350 Å – 2.375 Å). The diethylenetriamine crystal structures compared well. The conclusion was that the crystals prepared were diethylenetriamine hexachlororuthenate(III).
AFRIKAANSE OPSOMMING: Ruthenium(III), een van die platinum groep metaal-ione, is in hierdie studie ondersoek om die akwasie tempo konstante van [RuCl6]3- en die anasie tempo konstante van [RuCl5(H2O)]2- te bepaal. Dié twee reaksies verteenwoordig die ewewigsreaksie [RuCl6]3- + H2O ⇄ [RuCl5(H2O)]2- + Cl-. Die verloop van die reaksies is met behulp van UV/Sigbare spektroskopie by verskillende temperature gevolg. Die akwasie en anasie tempo konstantes is bepaal met goeie presisie en die termodinamiese konstantes van die reaksies is bereken. Die pseudo-eerste orde akwasie tempo konstante, k65, is bepaal deur middel van regressie, as 52.1 (±3.7) x10-3 s-1 by 25°C. Die aktiverings energie, Ea, is bereken as 90.1 (±1.2) kJ.mol-1 en die entalpie en entropie van aktivering is onderskeidelik 87.7 (±1.2) kJ.mol-1 en 24.7 (±4.3) J.K-1.mol-1. Daar is gevind dat die akwasie reaksie konstante afhanklik was van die soutsuur konsentrasie: dit neem af soos die soutsuur konsentrasie toeneem. Met behulp van die regressie lyn is die anasie tempo konstante bepaal by 25°C as 1.62 (±0.11) x10-3 M-1s-1. Die aktiveringsenergie is bepaal as 88.0 (±1.4) kJ.mol-1 en die entalpie en entropie van aktivering, onderskeidelik as 85.6 (±1.4) kJ.mol-1 en –11.2 (±4.7) J.K-1.mol-1. Die invloed van die soutsuur konsentrasie op die anasie tempo konstante is nie bepaal nie. Die ewewigskonstante vir die reaksie wat ondersoek is, is bereken met die tempo konstantes vir die akwasie en anasie reaksies. Die ewewigskonstante, K6, is bereken as 0.0311 M-1 by 25°C. Toe die ewewigskonstante vergelyk is met die literatuur waardes, is gevind dat die ewewigskonstante afhanklik is van die soutsuur konsentrasie. Saam met die waardes wat in die literatuur gevind is, is die ewewigskonstante gebruik om twee distribusie diagramme te bereken. Die distribusie diagramme vir die Ru(III) spesies toon onderskeidelik 79.9% en 72.3% [RuCl6]3- in 12M HCl. Die twee distribusie diagramme is baie eenders en dit is nie moontlik om ‘n finale distribusie diagram op te trek totdat die uitstaande tempo konstantes tussen die akwachloro Ru(III) spesies bepaal word nie. Die tempo konstantes en termodinamiese waardes wat bepaal is vir die Ru(III) reaksie is vergelyk met gelyksoortige waardes in die literatuur van Rh(III) en Ir(III) omdat daar ooreenkomste tussen die platinum groep metale opgemerk is. Daar is bevind dat die akwasie én anasie reaksies die volgende patroon volg: Ru(III) > Rh(III) > Ir(III). Die verskille word in sekere gevalle benut in die raffinering van hierdie metale. Kristalle van dietileentriamien heksachlororuthenaat(III) is berei en gekarakteriseer met behulp van CHN analise en x-straal kristallografie. Die gemiddelde Cl-Ru bindingsafstand vir die kristal was 2.371 Å. Die kristalstruktuur is vergelyk met dié van heksaäkwaäluminium hexachlororuthenaat(III) tetrahidraat en diëtileentriamien heksachlororhodaat(III). Die chloried-metaal bindingsafstand vir die kristalle was soortgelyk (2.350 Å – 2.375 Å). Die diëtileentriamien kristalstrukture stem goed ooreen. Die gevolgtrekking was dat die kristalle wat voorberei is wel diëtileentriamien heksachlororuthenaat(III) was.

This work has focussed on the preparation of a variety of tridentate ligands, designed to form ruthenium complexes as potential metathesis catalysts. Various approaches to the tridentate, malonate-tethered imidazolidine system have been investigated, and a promising route to accessing ligands of this type is discussed. A tridentate malonate-tethered pyridine ligand has been successfully prepared and its dithallium salt has been accessed by hydrolysis with thallium carbonate; approaches to a longer-chain analogue have also been investigated. A thallium pyridine-2,6- dicarboxylate ligand has been has been successfully prepared, as have a range of pyridine diamine ligands, with various alkyl and aromatic substituents on the amine donor atoms. Preliminary investigations into the potential of these compounds as ligands for alkylidene ruthenium complexes are reported using molecular modelling techniques. The geometries and steric energies of the ligands and their corresponding complexes have been analysed, and results obtained from two different software packages are compared. Finally, some preliminary complexation studies have been undertaken.

Chemistry
Ph.D.
Biogenic monoamines such as dopamine play an important role as major neurotransmitters. Simultaneous determination of the concentration changes is thus crucial to understand brain function. Additionally, quantification of pharmaceutically active compounds (PhACs) and their metabolites in biological fluids is an important issue for forensic tests, clinical toxicology and pharmaceutical analysis. We have developed two postcolumn luminescence detection methods coupled to a 2-dimensional-solid phase extraction (2D-SPE) system. The postcolumn reaction methods used in this study are the redox-dependent photoluminescence-following electron-transfer (PFET) and Fenton-based chemiluminescence techniques, for the determination of certain neurotransmitter and nonsteroidal anti-inflammatory drugs (NSAIDs). A stable [Os(tmphen)3]3+ (tmphen = 3,4,7,8-tetramethyl-1,10-phenanthroline) reagent was prepared in neutral aqueous solution by oxidation of [Os(tmphen)3]2+ with lead(IV) oxide. [Os(tmphen)3]2+ and [Os(tmphen)3]3+ are characterized by absorption spectroscopy. [Os(tmphen)3]3+ stability is compared with [Ru(tmphen)3]3+ in the same pH 7 environment. The properties of Os(III) and Ru(III) complexes were investigated for use as the oxidant in a PFET system. Studies of photophysical and electrochemical properties, the stability of the Os(III) and Ru(III) complexes, and analytical application in PFET detection of oxidizable analytes are presented. The spectroscopic properties of the complexes were not very advantageous, but careful control of the detection system and reaction conditions enabled sensitive detection of the analytes. The method was fully validated and the optimized system was capable of detecting dopamine and acetaminophen at about 30.2 µg L-1 and 33.5 µg L-1, respectively. The limit of detection (LOD) was 1.5 µg L-1 for acetaminophen and 4.3 µg L-1 for dopamine. The accuracy and precision were within bioanalytical method validation limits (90.9 to 101.5 % and RSD < 12.0 %, respectively). Typical analysis time was less than 15 minutes. Two Fenton-based flow-injection chemiluminescence (CL) methods were developed and validated for the determination of naproxen. Under the optimal experimental conditions the proposed methods exhibited advantages in a larger linear range from 2,760 ng mL-1 to 207,000 ng mL-1 for the first CL method and 41.4 ng mL-1 to 700.0 ng mL-1 for the second CL method. The LOD was 13.8 ng mL-1 for naproxen. The CL mechanisms for the system, H2O2-FeIIEDTA-naproxen was further studied by batch experiments, chemiluminescence spectroscopy, fluorometry, high pressure liquid chromatography (HPLC) and Fourier transform infrared spectroscopy (FTIR). The effects of various interferences commonly found in biological and wastewater systems on the chemiluminescence intensity were also investigated. We used these methods to determine NSAIDs in commercial pharmaceutical formulations. Another application of these method was for detecting NSAIDs in biological samples. A 2x-1-Dimensional Solid Phase Extraction (2x-1D SPE) method was developed for determination of acetaminophen and naproxen in urine. This method uses both the methanol concentration and the pH advantageously to preferentially isolate analytes of interest from complex sample matrix. These methods were fully validated and had sufficient sensitivity (limit of quantification: acetaminophen; 40.41 mg L-1 - 360.0 mg L-1 and naproxen; 23.03 mg L-1 - 214.8 mg L-1) for biological matrices and applications.
Temple University--Theses

The quenching of the [Ru(bipy)3]2+ by Cu2L2+ was studied and the data were plotted with the Stern-Volmer equation. The plot showed a break and was divided into 2 regions, <0.5 and >0.5 Cu2L2+: [Ru(bipy)3]2+ molar ratio. Quenching above the 0.5 Cu2L2+: [Ru(bipy)3]2+ molar ratio was slower (330 x 10-6 M-1s-1) than the quenching rate reaction below 0.5 ratio (387 x 10-6 M-1s-1). With Cu2L2+ being a dimeric complex the break and differences in the quenching reaction rates can be explained in terms of the stoichiometry. When the Cu2L2+: [Ru(bipy)3]2+ ratio is < 0.5, then each [Ru(bipy)3]2+ can interact with 1 Cu2L2+ dimer. At 0.5 then there is exactly a 1:1 ratio RuII : CuII. Above the 0.5 ratio the [Ru(bipy)3]2+ can interact with maybe only one of the Cu2L2+'s in the dimer, or with a [Ru(bipy)3]2+: Cu2L2+ unit, so the quenching is less efficient.

In dye-sensitized solar cells, the functions of light absorption and charge transport are separated. A photosensitive ruthenium-polypyridine dye in the cell absorbs light, injects an electron to a semiconductor and is then regenerated by a redox couple, typically iodide/triiodide. Quantum chemical calculations of the electronic structure of triiodide have been carried out with the restricted active space SCF method, including spin-orbit coupling, and with density functional theory. It was shown that the difference in charge density between the terminal and central atoms results in a splitting of the core levels. The calculations gave a value of the splitting of 0.8 - 1.0 eV for the 3d and 4d levels. Experimentally, the electronic structure has been investigated with photoelectronspectroscopy. The measured terminal/center splitting is 1.1 eV.The spin-orbit interaction of the 4d levels of triiodide has also been calculated. The splitting was determined to be 1.6 eV. The experimental value is 1.7 eV. An assignment of the peaks in the computed spectrum of triiodide was made and the features of the experimental spectrum have beenidentied.The theoretical valence spectrum of triiodide has been computed and assigned. The results can be used in the analysis of photoelectron spectra of the molecule. Information about the electronic structure of the redox couple can help in the understanding of the electron transfer processes and forfurther development of the solar cells.  Furthermore, the solvation structure of the prototype dye, the tris(bipyridine)ruthenium(II) complex, in water and its interaction with iodide and chloride has been studied by means of molecular dynamics simulations. The trajectory analysis showed that the water molecules in the first solvation shell form a chain in between the bipyridine ligands. It was found that the iodide ions are more likely than chloride to enter between the ligands, which can be important for the electron transfer processin the solar cell.

Our research involved two projects: Crown Aza and Crown ether. Crown Aza are compounds that have nitrogens as the hetero-atoms in the macrocycle. In the first aim, the 1 H NMR spectrum of strongly-coupled di-iron complexes shows 5 different conformations, but is unable to identify these conformers. Calculation using Density Functional Theory (DFT) were performed to attempt to quantify these conformers to correlate with the experimental NMR data. The second aim of this study was to utilize the carbonyl functional group of the macrocycles to couple the iron complexes to obtain tetramers or higher oligomers. Visible spectra of the selective reduction of iron mono-keto-macrocycles with boron trifluoride and triethylsilane showed a coupling reaction to form a di-iron complex. A mixture of iron mono-keto-macrocycic with iron diketo-dimacrocycle showed a new species with an intense NIR absorption at 1010 nm. This intense band at 1010 nm is extremely rare in transition metal compounds and is of potential interest in photodynamic therapy. This indicates a new species is formed with a very low energy gap between the ground and excited states. Our second interest is in ionizable crown ethers that have many potential applications from environmental to medical. These macrocyclic poly-ethers contain phosphorous and oxygen atoms which produce a charged moiety in the ring to form a neutral complex with our targeted ions. They are significantly different from all ionizable cyclic poly-ethers in the literature. They vary in ring size from 16-crown-6 to 22-crown-8 using ethylene or propylene linkages between the oxygen atoms. Theoretical calculations revealed these ionizable crown ethers can accommodate ions from 2.6 angstroms to 4.2 angstroms in diameter. Strontium 90 ( 90 Sr 2+ ) is a radioactive product ion from nuclear fission reactions. The Phosphorous containing macrocyclic poly-ether with 2 charges could form complexes with Strontium and are possible candidates for clean-up agents of radioactive materials. The synthesis of ionizable crown ethers is discussed.

Measurement and mapping of the pressure distribution across the surface of a suitably scaled model is an integral step in the design of any aircraft or automobile. For this purpose, the traditional workhorses of the aeronautic and automotive industries have been pressure taps--small orifices that contain electronic pressure transducers. Unfortunately, in addition to the limited spatial resolution achievable with such devices, their technical complexity and cost constitute serious disadvantages. For more than 35 years, researchers have pursued a fundamentally different alternative: indirect measurement of pressure via oxygen-induced quenching of the luminescence emitted by certain chemical species. Porphyrin complexes of dipositive palladium and especially platinum have emerged as one of the principal classes of oxygen-sensitive luminophores; ruthenium(II) polypyridyl complexes comprise another. Various other metals also form luminescent coordination complexes that are susceptible to quenching by O2, however, and these too have contributed to the diversity of luminophores that are now available for incorporation into pressure-sensitive paints and related films and coatings. After treating the photophysics of luminescence quenching by molecular oxygen and quantitative descriptions of this phenomenon in the ideal case and in heterogeneous media, the thesis presents a comprehensive survey of the chemical literature on oxygen-sensitive luminophores. Efforts to prepare and characterize a novel porphyrin-pillared mixed zirconium phosphonate are then detailed. Following complexation of Pt(II) ions by the porphyrin moieties, this material is expected to display oxygen-sensitive luminescence and should ameliorate such difficulties as luminophore aggregation and matrix photodegradation that are associated with many existing pressure-responsive coatings. Its preparation necessitated preliminary formation of a porphyrin functionalized with two phenylphosphonic acid groups, which was obtained by synthesizing dipyrromethane and diethyl 4-formylphenylphosphonate and condensing these two precursors. The mixed phosphonate, a layered material assembled from ZrOCl2 · 8H2O, methylphosphonic acid, and the aforementioned porphyrin, was then prepared in refluxing HF. Solid-state 31P NMR spectra and powder X-ray diffraction patterns were acquired for the final product, its estimated interlayer spacing of 22.8 Å figuring prominently in analysis and discussion of the X-ray data.

The bite angle of a diphosphine ligand plays an important role in determining the reactivity of a transition metal complex. The coordinated dihydrogen on a transition metal center can be activated toward homolysis or heterolysis depending upon the nature of the metal center and the ancillary ligand environment. The present work deals with our investigations on the effect of the bite angle of the chelating diphosphine ligands in the chemistry of certain ruthenium hydride and dihydrogen complexes. Protonation of the ds-[Ru(H)2(dppm)(PPh3)2] (dppm = Ph2PCH2PPh2) using HBF4-Et2O resulted in the dihydrogen/hydride complex trans-(Formula). This species shows dynamic exchange of the H-atom between the dihydrogen and the hydride ligands. The H-atom site exchange was studied by NMR spectroscopy. Attempts to prepare the ruthenium dihydride complexes, cis-[Ru(H)2(dppe)(PPh3)2] (dppe = Ph2PCH2CH2PPh2) and cw-[Ru(H)2(dppp)(PPh3)2] (dppp = Ph2PCH2CH2CH2PPh2) with larger bite-angled diphosphines dppe and dppp were unsuccessful. Earlier work in our group on the effect of trans nitrile ligands in a series of complexes of the type (Formula)howed that the properties of the bound H2 are almost invariant with a change in the R group of the nitrile. hi an effort to compare those results with analogous ruthenium complexes bearing smaller bite-angled diphosphine, dppm, we synthesized and characterized a series of complexes of the type (Formula). We found that the properties of the bound H2 were once again invariant with a change in the R group of the nitrile. In an effort to compare the effect of having two diphosphine ligands of different bite angles with systems containing symmetrical diphosphine ligands reported by our group,3 we synthesized a series of complexes of the type (Formula). These complexes exhibit hybrid properties in comparison to systems with symmetrical diphosphine ligands in terms of spectroscopic features and chemical reactivity. Thus, the bite angle of the diphosphine ligand has a definite influence on the properties of the bound H2 ligand.

Chemistry
Ph.D.
Development of therapeutics is an extensive process, consuming significant amounts of time and requiring herculean synthetic efforts. A new therapeutic is most often designed from a previously commercialized scaffold, to increase the chance of success. Designing new molecular scaffolds can be extremely high risk and time consuming, yet at the same time the reward can be substantial. Accessing new molecular scaffolds, with efficient and “green” methods, is important in modern medicinal chemistry to diversify chemical space for therapeutic targets. There may be significant quantities of therapeutic candidates that have been over-looked due to synthetic challenges. There is a need for methodologies to synthesize challenging molecular scaffolds that are underexplored in commercialized therapeutics. The work described herein employs two distinct methodologies to access complex molecular scaffolds: 1) by developing a titanium (II) mediated Kulinkovich de-Meijere reaction arrested by Bredt’s rule and a suitable aryl sulfonyl moiety to afford diverse molecular scaffolds with potential for medicinal chemistry applications and 2) utilizing a [4 + 4] photocycloaddition of 2-pyridone-enolynes to access functionally rich cyclooctanoids that are capable of further photochemical transformations into even more complex molecular scaffolds. The titanium (II) mediated Kulinkovich reaction traditionally yields cyclopropylamines and cyclopropanols from amides and esters, respectively. The reaction involves two consecutive carbon-carbon bond forming steps. The bridged tricyclic intermediates would violate Bredt’s Rule and prevent the final carbon-carbon bond formation. This transformation can access a wealth of cyclic amino-ketones from olefin-tethered lactams. In addition, appropriate selection of an electron withdrawing group on nitrogen achieves the same bond sequestration. Interception of the titanafuran intermediate allows for electrophilic trapping of the titanium-carbon bond. The electronically arrested second carbon-carbon bond forming step adds generality to the interrupted Kulinkovich de-Meijere reaction to access the challenging molecular scaffolds of trans-α,α’-disubstituted cyclic ketones. Intramolecular [4 + 4] photoreaction of 2-pyridones with silyl 3-enol-1-ynes yields a highly reactive 1,2,5-cyclooctatriene. In the presence of a silanol proton source the allene is converted into a 1,3-diene. Without the combination of silyl 3-enol-1-ynes and silanol, as previously reported with 1,3-enynes, complex mixture of products is observed. Use of more nucleophilic solvents results in near quantitative yield of the cyclooctadienone through loss of silicon. Further photochemical manipulations of the cyclooctanoids allows for rapid scaffold diversification into bullvalene-like structures through a di-π-methane rearrangement.
Temple University--Theses

Desenvolveu-se um método espectrofotométrico para determinação de íons Cu(II), Fe(II) e Fe(III) com o reagente cromogênico di-2-piridil cetona benzoilhidrazona (DPKBH), em condições estacionárias e em fluxo. Fez-se a caracterização estrutural e estequiométrica do complexo de Cu(II) com DPKBH usando-se técnicas espectroscópicas de infravermelho e massas, além de análise térmica e elementar. Estudou-se, ainda, a estequiometria dos complexos de Fe(II) e Fe(III) com DPKBH utilizando espectrometria de massas com ionização por electrospray. Desenvolveu-se, preliminarmente, um método espectrofotométrico para a determinação de íons Cu(II) com DPKBH e aplicou-se em amostras de aguardente. Posteriormente, adaptou-se para análise por injeção em fluxo, utilizando-se injetor comutador manual. Em seguida, desenvolveu-se em condições estacionárias um método espectrofotométrico para determinação de Fe(II) e Fe(III) e Cu(II) em uma mesma amostra, com o uso de agentes mascarantes. Fez-se também a adaptação do método para análise em fluxo empregando multicomutação e amostragem binária. Finalmente, determinou-se a concentração de íons Cu(II), Fe(II) e Fe(III) em amostras sintéticas e Cu(II) e ferro total em amostras de sedimento coletadas no reservatório de Guarapiranga. Os resultados obtidos foram comparados com o método de referência de ICP-OES, apresentando concordância para um nível de confiança de 95% da média.
A spectrophotometric method was developed to the determination of Cu(II), Fe(II) and Fe(III) with the chromogenic reagent di-2pyridyl ketone benzoylhydrazone (DPKBH) in stationary conditions as a flow injection process. The structural characterization and the stoichiometry of Cu(II)/DPKBH complex were achieved using infrared spectrometry, mass spectrometry, thermal and elementar analysis. Toe stoichiometry of the Fe(II) and Fe(III) complexes with DPKBH was studied by electrospray ionization mass spectrometry. The spectrophotometric method for the determination of Cu(II) with DPKBH was developed in stationary conditions and, after this, it was adapted to flow injection analysis, using a manual commutator. Subsequently, a spectrophotometric method was developed to determine Fe(II), Fe(III) and Cu(II) in the same sample, in stationary conditions, using masking reagents. This method was also adapted to flow injection analysis, using multicommutation and binary sampling. Finally, Cu(II), Fe(II) and Fe(III) were determined in sediments from Guarapiranga reservoir. The obtained results were compared with the ICP-OES standard methods, showing a good agreement into a 95% confidence level (t-test).

A new POCOP pincer-type ligand was synthesized and characterized. This new ligand gave rise to the first POCOP pyridylidene pincer-type ruthenium and iridium complexes. Investigations into structural and electronic parameters of these newly generated compounds were conducted. Furthermore, we prepared ruthenium dihydrogen and bis-dihydrogen complexes and studied them via deuterium labelling and low temperature NMR spectroscopy. These complexes were screened for catalysis in C-C coupling, C-H bond activation and ketone hydrogenation reactions.

Ruthenium carbene complexes, with the general structure, [LL’Ru=CHR], are commonly known as Grubbs type catalysts, named after the discoverer of these metathesis catalysts. The discovery was quite revolutionary, since the catalysts proved to be easy to handle, tolerant towards various functional groups and more stable with regard to air and water than previous transition metal catalysts. Another important advantage was that all types of olefin metathesis reactions could be initiated without the help of co-catalysts or promoters. Today Grubbs type catalysts find wide application in especially organic and synthetic chemistry. A well-known example is the SHOP-process which produces long chain -olefins, while other important applications include the synthesis of macro-cyclic and cyclic olefins. The current study involved experimental and theoretical work to investigate various aspects comprising synthetic procedures, reactivity, kinetics, geometry and electronic properties of the complexes. Results are discussed briefly in the following paragraphs. The first aim of the project was to synthesise a Grubbs type catalyst. Initial efforts were focused on the preparation of a first generation catalyst through various methods. This included modifying the reported method for the synthesis of [(PPh3)2Cl2Ru=CH-CH=CMe2] to yield [(PPh2Cy)2Cl2Ru=CHCH= CMe2] instead; a phosphine exchange reaction with the complex [(PPh3)2Cl2Ru=CH-CH=CMe2] and free phosphine PPh2Cy; and utilising the analogue arsine ligand, AsPh3, to synthesise [(AsPh3)2Cl2Ru=CHCH=CMe2]; but unfortunately no success was achieved. However, it was possible to synthesise a novel second generation Grubbs type catalyst, [(IMesH2)(PPh2Cy)Cl2Ru=CHPh], through the phosphine exchange reaction of [(IMesH2)(NC5H5)2Cl2Ru=CHPh] and PPh2Cy. The new complex was tested in kinetic reaction studies and phosphine exchange reactions. Results showed that [(IMesH2)(PPh2Cy)Cl2Ru=CHPh] was catalytically active for the ring closing metathesis of commercial diethyl diallylmalonate. The reaction was first order with regard to the olefin, contrary to the second order kinetic results reported for similar reactions catalysed by first generation Grubbs catalysts. The phosphine exchange reactions were very successful and a rate constant could be determined. The rate constant was independent of the free phosphine concentration and activation parameters had relatively large, positive values; results indicative of a dissociative mechanism. These findings are in correlation with literature reports. A kinetic investigation was done on the catalyst-olefin coordination involving the functionalized olefins vinyl acetate, allyl acetate and allyl cyanide; and the first generation Grubbs catalyst, [(PCy3)2Cl2Ru=CHPh]. A two-step rate law, similar to an interchange mechanism, was determined. Phobcat, [(PhobCy)2Cl2Ru=CHPh], is modified first generation Grubbs type catalyst with rigid bicyclic phosphine rings which was recently developed by the Sasol Homogeneous Metathesis Group. In the current study Phobcat was compared to Grubbs1-PCy3 in the cross metathesis reaction of 1-octene. Results showed that Phobcat was up to 60% more active and had a 5 hour longer lifetime than Grubbs 1-PCy3. Theoretical studies were done on the three functionalized olefins of the earlier experimental study to gain fundamental understanding of steric and electronic influences on these catalyst-olefin systems. Without exception, coordination via the heteroatom of the olefin was significantly more favourable than coordination via the double bond functionality. This result indicates that metathesis of these olefins is highly unlikely, since the stable heteroatom coordination will suppress the parallel Ru=C/C=C interaction which is compulsory for the metathesis reaction. Orbital studies highlighted the difference between coordination of acetate and cyanide, but no trend of an electronic nature could be recognised.
Prof. A. Roodt

The chemistry of aqueous Ru^(II)(H_2O)_6(tos)_2(tos = p-toluene sulfonate)(1) with functionalized olefins has been investigated. Complexes of the type (H_2O)_5Ru^(II)(olefin)(tos)_2 are formed from 1 and monoolefins. Dienes such as diallyl ether and 1,5-hexadiene displace two aquo ligands from 1 to form chelate complexes of the type (H_2O)_4Ru^(II)(olefin)_2(tos)_2. Chelation of oxygen containing functionalities such as alcohols, ethers, and sulfonates has also been observed when the functional group is a specified distance from the olefin. Thus, 3-buten- 1-o1, 3-butenyl methyl ether, and 2-propenesulfonate anion form chelate complexes Ru^(II)(H_2O)_4(η^1(O): η^2(C,C')-HOCH_2CH_2CH=CH_2)(tos)_2, Ru^(II)(H_2O)4-( η^1(O): η^2(C,C')-CH_3OCH_2CH_2CH=CH_2)(tos)_2, and Ru^(II)(H_2O)_4(η^1(O): η^2(C,C')OSO_2CH_2CH=CH_2)(tos), but allyl ethyl ether forms only the olefin complex Ru^(II)(H_2O)_5(η^2(C,C')-CH_2=CHCH_2OCH_2CH_3)(tos)_2. Carboxylic acid functionalities react irreversibly with 1 to form carboxylate complexes. 3-Pentenoic acid reacts with 1 yielding the bis(olefin)-bis(carboxylate) complex Ru(H_2O)_2(η^1(O), η^2-(C,C’)-OCOCH_2CH=CHCH_3)_2 which has been structurally characterized. Olefin isomerization of allylic ethers and alcohols is catalyzed by 1 under mild conditions in aqueous solution to yield the corresponding carbonyl compounds. Non-allylic olefins are also isomerized, although homoallylic alcohols exhibit stability towards isomerization. An exclusive 1,3-hydrogen shift is observed in the 1-catalyzed isomerization of allyl-1,1-d_2 alcohol to propionaldehyde-1,3-d_2 and allyl-1,1-d_2 methyl ether to 1-propenyl-1,3-d_2 methyl ether. The presence of crossover products from the isomerizations of mixtures of (a) allyl-3-^(13)C alcohol and allyl-1,1-d_2 alcohol and (b) allyl-1,1-d_2 methyl ether and allyl ethyl ether demonstrates that the isomerization of both ethers and alcohols occurs via intermolecular hydrogen shifts. A modified metal hydride addition-elimination mechanism involving exclusive Markovnikov addition to the double bond directed by the oxygen functionality of the substrate has been proposed. The acyclic terminal olefins 3-buten-1-ol and methyl acrylate are effective chain transfer agents in the ROMP the 7-oxanorbornene derivative 5,6-exobis(methoxymethyl)-7-oxabicyclo[2.2.1]hept-2-ene by 1, providing the first example of acyclic olefin metathesis in this system. Oligomer samples with M_n as low as 2K have been prepared. End groups corresponding to the alkylidene moieties of the chain transfer agents have been identified in the ^1H and ^(13)C NMR of the oligomer mixtures. Connectivity has been established between these end groups and the polymer chain through two-dimensional ^1H NMR. Ring-opened monomer units end capped by the chain transfer agent have been identified by mass spectrometry techniques.

Polypyridine d6 and d8 transition metal complexes have received a great deal of attention because of their wide applications in various areas such as photo-induced energy- and electron-transfer process, artificial photosynthetic centers, electroluminescent displays, dye-sensitized solar cell, and molecular-level machines, etc Compared to 2, 2'-bipyridine-type complexes, 2, 2':6', 2″-terpyridine(tpy)-type complexes have been much less thoroughly examined, because the weak ligand field of tpy-type ligands results in the weak emissive and short-lived excited states of their complexes. However, tpy-type complexes have geometrical advantages, which are achiral and could lead to linear structures upon introduction of substituents at 4'-position of tpy The goal of this work is to overcome the short excited state lifetime drawback of the tpy-type complexes by the development of novel tpy-type ligands, so as to develop long-lived excited state sensitizers potentially for light-harvesting applications Oligo(phenylene-vinylene) (OPV) and derivatives, which are strong luminescent chromophores with semiconducting and electroluminescent properties, were employed to modify the tpy ligand at the 4'-position. Two series of OPV-tpy ligands (mono-tpy and bridging tpy-OPV-tpy ligands) with varying substituents like electron-donating groups (n-C8H17O- and Me2N-) and electron-withdrawing group(-CN) at different positions, were successfully synthesized by means of Wittig-type reactions and the Knoevenagel reaction OPV-tpy and bridging tpy-OPV-tpy ligands show strong luminescence. Their Zn(II) complexes also display strong luminescence with relatively higher quantum yields than the corresponding free ligands. The absorption and luminescent spectra of the free ligands were found to be red-shifted by increasing the length of the phenylene-vinylene or introducing electron donating groups. The Me2N- containing ligand, Me2Npvpt shows strong emission solvatochromism. By varying the solvent polarity, its emission colors were finely tuned to cover the entire visible range from blue (426 nm, Ф = 0.25) in the non polar solvent hexane, to red (626 nm, Ф = 0.52) in the highly polar solvent DMSO. The Zn(II)-induced solvatochromism wase observed in OPV-tpy ligands A series of monometallic Ru(OPV-tpy)22+ complexes and bimetallic [(mpt)Ru(tpy-OPV-tpy)Ru(tpm)]4+ complexes were prepared. All the complexes show very close energy singlet metal-ligand charge transfer (MLCT) transitions and similar electrochemical behaviors. However, progressive changes in the emission, transient absorption and excited state lifetime (tau) were observed. The tau shows a 6000 fold magnitude difference from one vinylene Ru1vRu complex (tau = 14ns, lambdaem max,r,t = 684nm), two vinylene Ru2vRu (tau = 280ns, lambda em max,r,t = 697nm), to four vinylene Ru4vRu complex (tau = 60,000 ns, lambdaem max,r,t = 773nm). Combined spectral data suggest that the energy gap (DeltaE) between triplet MLCT and triplet intraligand (3IL) transitions determines the excited state lifetimes. When DeltaE is large, if 3MLCT is the lowest lying state, tau is very short; if 3IL is the lowest lying state, tau is significantly long. When DeltaE is very small, a long-lived 3MLCT transition might occur, due to reversible energy transfer from 3IL to 3MLCT A series of [Pt(OPV-typ)Cl]+ complexes were synthesized. The long-lived (1 mus - 10mus) phosphorescence with predominant 3pi-pi* in nature was observed in both non-coordinating and coordinating solvents. The transient absorption spectra show ground state bleaching and excited state absorption from visible to far red
acase@tulane.edu

The goal for this research described herein is the development of a series of transition metal based visible light absorbing chromophores that have excited state lifetimes long enough to actively participate in bimolecular photoreactions and display both two photon excited state absorption and reverse saturable absorption properties. With this goal in mind, the preparation and photophysical characterization of a series of metal-organic Ru(II) and Os(II) complexes with relatively long excited state lifetimes is presented. The approach to extend the excited state lifetimes is to make Ru(II) and Os(II) complexes with ligands having triplet state energies that can be sensitized by long wavelength excitation into metal-to-ligand charge transfer MLCT transitions of the complexes. An additional characteristic of the complexes that is introduced through the introduction of ligands with low energy triplet states is unique excited state absorption in the near infra-red. The combination of long excited state lifetime and unique excited state absorption demonstrates the potential use of complexes as optical limiting materials (protection of materials from pulsed laser sources) Three areas of interest for this project are addressed here. First, is the determination of triplet energies of aryl vinylene terpyridyl and bipyridyl aromatic hydrocarbon ligands using density functional calculations (B3LYP with a 6-31G* basis running on Gaussian 03 or Gaussian 09) and the synthesis of some of the ligands under Wittig or Knoevenagel conditions. Second is the coordination of the ligands on the ruthenium and osmium metal centers and the subsequent photophysical. Third, is the evaluation of the utility of the complexes as optical limiting materials by a variety of characterization methods including evaluation of intersystem crossing efficiencies, determination of two photon absorption coefficients and determination of rate constants for formation of the triplet absorbing states of the optical limiters The project, which was a cooperative effort with three different groups, was to develop and characterize a new class of aryl-vinylene derivatized bipyridine and terpyridine ligands and long wavelength absorbing organometallic complexes for optical limiting purposes. The complexes were made in our group and further investigated in Emory University by Dr. Tim Lian's group using femtosecond transient spectroscopy; their two photon absorption properties were characterized by Z scan methods in Dr. Igor Rubtsov's group at Tulane University Photoredox reactions of this series of Ru(II) and Os(II) complexes in solution were also examined. These metal complex chromophores couple excited states localized on the metal complex (MLCT) with states of triplet spin multiplicity on a covalently linked organic (aromatic hydrocarbon) component. For the bis-bipyridine Ru(II) complexes the pyrenylvinyl 'localized' excited state of the complex reacts via photoinduced electron transfer with a variety of viologen and diquat electron acceptors. The interesting aspect of the electron-transfer process is that though the excited state is ligand-localized the photoredox reaction product is oxidized Ru(III) The determination of triplet yields, examined by energy transfer experiments, gave us an idea of the effectiveness of intersystem crossing to populate the triplet ligand localized state in a series of ruthenium complexes. Preliminary Z scan measurements demonstrate that some of the ruthenium and osmium complexes are good candidates for optical limiting materials by virtue of their relatively large two photon absorption coefficients at wavelengths of particular interest for laser protection. Femtosecond transient spectra demonstrate that population of the triplet ligand localized states is very fast (less than 5ps) A final chapter is included which represents a continuation of the work of Dr. Jin Chen. Four ruthenium diimine complexes have been synthesized as phosphorescent oxygen sensors
acase@tulane.edu

碩士
國立臺灣大學
化學研究所
99
We have successfully prepared 2,8-di(2-pyridyl)-5-phenyl-l,9,10-anthyridine (4a), which is a multidentate ligand. For the ligand synthesis, the double Friedlander condensations of 2,6-diamino-4-phenylpyridine-3,5-dicarboxaldehyde (3) with 2-acetylpyridine yielded 4a. Coordination of 4a with two kinds of ruthenium precursor, RuCl2(CO)3(THF) and [(η6-p-cymene)RuCl2]2 , resulted in the formatioon of a mono-nuclearspecies ([(4a)Ru(CO)3Cl)(Ru(Cl)3(CO)3]) (Ru1) and a dinuclear ruthenium complex ([(4a)Ru2(p-cymene)2(Cl)2][(PF6)(Cl)]) (Ru2), respectively. Two complexes were characterized by X-ray crystals, NMR, ESI-MASS. We had found that one of the p-cymene of Ru2 is fluxional, and we proposed that the p-cymene might vibrate when Ru2 is dissolved in solvent. The vibrate frequency and free energy was determined by the low-temperature 1H NMR experiment. In the catalytic application, mono- and di-nuclear ruthenium complexes were active for the cyanation of tertiary amines with sodium cyanide. Complex Ru2 afforded the corresponding a-aminonitriles with good yields with hydrogen peroxide as the oxidant under acidic condition.

One microfiche--`Data from crystal structures solved by the author`--in pocket
Bibliography: leaves 172-174
174 leaves : ill ; 30 cm.
Title page, contents and abstract only. The complete thesis in print form is available from the University Library.
Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1987

This thesis work is based on an investigation of intermediates involved in various metal mediated catalytic reactions such as hydrogenation, hydroboration, functionalization of methane etc. An intermediate dictates the energetics of the catalytic cycle of these reactions. Therefore, it is important to study such types of intermediates in order to design a better catalyst. These intermediates are called σ-complexes in which a σ-bond is coordinated to the metal center at some stage of the reaction coordinate. These species are rarely stable at ambient conditions which create difficulties in exploring their chemistry. Our aim is to study the effect of ancillary ligands on the coordination properties of a σ-bond ligand. We chose two different classes of σ-complexes – one contains a B–H σ-bond as a ligand, i.e., σ-borane complex and another contains a H–H σ-bond as a ligand, i.e., σ-dihydrogen complex. Both M–H–B and M–H2 interactions are 3-center-2-electron coordination bonds comprised of two bonding components. One is σ-donation, which is present in both and another is π-back donation from the metal center, which is negligible in the σ-borane complexes contrary to the σ-dihydrogen complexes. The bonding characteristics of M–H–B and M–H2 interactions suggest that an electron deficient metal center is necessary to study the σ-borane complexes with reasonable stability. Thus, we selected an early transition metal, i.e., Cr(0) bearing arene and CO ancillary ligands, for studying the σ-borane complexes. On the other hand, the cis-dihydrogen/hydride and cis-dihydrogen chloride complexes were studied on a late transition metal center, i.e., Ru(II) bearing phosphine and N–N bidentate ligands. Ammonia-borane is known to be a potential hydrogen storage material. Therefore, we picked up the catalytic dehydrogenation reaction of this compound and intended to investigate the interaction between a metal center and the BH σ-bonds of amine-boranes. We characterized the σ-borane complexes [(η6-arene)Cr(CO)2(η1-H–BH2•NMe3)] (arene = fluorobenzene, benzene, and mesitylene), and observed an interesting correlation between the electronics and stability of these species. This was the first report of σ-borane systems possessing an η6-arene ligand. A prototype homobimetallic σ-borane complex, [(η6-C6H5CH2NMe2•BH2–HCr(CO)5)Cr(CO)3] was characterized using single crystal X-ray crystallography. An intramolecular σ-borane complex, (η1-(η6-C6H5CH2NMe2•BH2–H))Cr(CO)2 was found to possess an interesting chelation of the η6-arene, and BH coordination sites of its amine-borane moiety with the Cr(0) center. These σ-borane complexes showed an interesting dynamics in the binding interface between the metal center and the borane ligand. Free energy of activation (ΔG#) for this process was estimated to be 30-40 kJ/mol. To explore certain σ-dihydrogen complexes we investigated the chemistry of cis-dihydrogen/hydride complexes of Ru(II) bearing phosphine and N-N bidentate ligands cis,trans-[RuH(η2-H2)(PPh3)2(N-N)][OTf] (N-N = 2, 2′-bipyridyl, 2, 2′-bipyrimidine) in detail. In those cases, we established that the adjacent hydride ligand has large influence on the dihydrogen coordination. The η2-H2 and hydride ligands showed a single 1H NMR spectral signal due to fast site exchange among each other. We established the mechanism and calculated the free energy of activation (ΔG# = 8-13 kJ/mol) of this dynamics. These complexes were found to be stable at ambient conditions although, a labile dihydrogen ligand is present in the coordination sphere of the metal center. In fact, we could obtain the single crystals of cis,trans-[RuH(η2-H2)(PPh3)2(bpy)][OTf]. The molecular structure of a σ-complex in which a σ-bond (before it gets completely formed or broken) acts as a ligand is what fascinates this area in chemistry. A cis-dihydrogen chloride complex, cis,trans-[RuCl(η2-H2)(PPh3)2(bpm)][OTf] was characterized unambiguously using NMR spectroscopy. The H-H distance (dHH) for the η2-H2 ligand of these complexes were estimated to be 0.9-1.0 Å. We attempted to observe some σ-methane species spectroscopically at low temperatures. Unfortunately, these species were quite unstable for exhibiting the NMR spectral signals even at low temperatures. Nevertheless, we investigated the reactivity of cis,trans-[RuHX(PPh3)2(N-N)] (X = H, Cl; N-N = 2, 2′-bipyridyl, 2, 2′-bipyrimidine) towards a methylating agent, CH3OTf. This reaction resulted in methane evolution by the combination of the hydride ligand of a Ru(II) complex and the CH3+ moiety of CH3OTf. This reaction was carried out in a sealed tube inside a NMR probe at ~183 K and monitored for a long period of time; however, the methane bound metal species was not observed. Perhaps, the longevity of this class of σ-methane complex falls below the NMR time scale.

Nucleophilic additions are an important class of reactions in the preparation of several organic compounds. Metals facilitate nucleophilic additions in many cases. The present work Mechanistic Investigation of Metal Promoted Nucleophilic additions is an attempt to understand the mechanism of nucleophilic additions to imines and carbonyl compounds mediated by the transition metal complexes. Understanding the mechanism of metal promoted nucleophilic additions can facilitate the design and synthesis of more efficient catalysts. Chapter 1 provides a brief introduction to nucleophilic addition. A few named reactions that involve nucleophilic addition are described. An overview of the metal promoted nucleophilic addition reactions and their mechanisms are presented. A short note on the importance of understanding the mechanism of metal promoted nucleophilic addition is included. This section ends with the scope of the present work. Chapter 2 “Mechanistic Investigation of Titanium Mediated Reactions of Imines” deals with two reactions. The first reaction is the formation of reduced amines on reduction of imines. Amines and diamines are synthesized often from imines. A convenient route to such nitrogen containing compounds is through reduction of imines and through reductive coupling of imines respectively. Since both reactions occur in a parallel fashion, during the synthesis of diamines, amines are obtained as side products and vice versa. This problem is acute in the case of titanium based reducing agents. These reducing agents are called low valent titanium reagents because low valent titanium species are generated in situ either from titanium(IV) or titanium(III) reagents. There is no clear understanding of the nature of the low valent titanium involved in the reaction. To rectify this, a mechanistic understanding of this reaction is essential. An attempt was made to probe the mechanism of formation of amines using low valent titanium formed by using two different reducing agents namely phenylsilane and zinc. With the help of isotopic labelling studies, it was found that the mechanism of formation of an amine with phenylsilane involves a direct hydrogen transfer from phenylsilane to an imine. This was verified using deuterium labelled phenylsilane. With zinc, it follows a traditional titanacycle pathway which was verified by quenching with the deuterium oxide. A second reaction that has been probed is the alkylation of imines by Grignard reagents using chiral titanium complexes. Alkylation of imines is one of the suitable routes to prepare chiral amines. Alkylation of imines employing a Grignard reagent with Ti(OiPr)4 can proceed through two different pathways depending on the amount of the Grignard reagent used. Alkylation reaction with one equivalent of Grignard reagent can proceed through a Ti(IV) species and the alkylation reaction with two equivalents of the Grignard reagent can proceed through a Ti(II) species. The reaction proceeding through Ti(IV) is less wasteful as it only requires one equivalent of the Grignard reagent. The two pathways differ from each other in the nature of the transition state where the C-C bond is formed. To verify the favourable pathway, chiral titanium complexes were prepared and alkylation carried out. The alkylation results suggest that one equivalent of Grignard is sufficient to give good yields of the alkylated product and the reaction may proceed through a Ti(IV) promoted path. It was reported in the literature that at least three equivalents of Grignard reagent are required to get good yields of the alkylated product with zirconium complexes. This work suggests a greener alternate to alkylation of imines. Chapter 3 “Asymmetric Transfer Hydrogenation Reaction of Ketones in Water” deals with the synthesis of chiral ruthenium half-sandwich complexes employing a proline diamine ligand which has phenyl, ethyl, benzyl, or hydrogen as a substituent. These complexes were characterized by X-ray diffraction. In addition, all these complexes were obtained as single diastereoisomers. These complexes were used as catalysts for the reduction of a variety of ketones to chiral alcohols in water using sodium formate as a hydride source. Stoichiometric reaction between sodium formate and the catalysts showed the formation of hydride complexes as the active species. Based on the electronic effects observed, the key step is found to be a nucleophilic attack of hydride on the carbonyl carbon of ketones. In the transfer hydrogenation reaction with DCOONa, more of 1-phenylethanol- 1-2H1 was observed with all the ruthenium catalysts suggesting that the hydrogen from sodium formate is transformed into a metal hydride which is subsequently transferred to the ketones to form chiral alcohols. The catalysts were optimized with acetophenone as a model substrate. Only in the case of a catalyst which has a phenyl substituent, silver nitrate was found to enhance the formation of aqua complex which in turn resulted in good yields of the chiral alcohols. Among all the complexes studied, the catalyst bearing a phenyl group induces greatest enantioselectivity. It can also be recycled. Chapter 4 “On the Formation of a Ruthenium-PPh2H Complex Using 1- Phenylethane-1,2-diol” deals with the mechanism of formation of PPh2H from PPh2Cl. This unique transformation involves a ruthenium-cymene dimer, PPh2Cl and 1-phenylethane-1,2- diol. In the attempted synthesis of a ruthenium bisphosphinite complex, using the ruthenium-cymene dimer, chlorodiphenylphosphine and 1-phenylethane-1,2-diol, the formation of [Ru(η6-cymene)Cl2PPh2H] was observed in good yield. Formation of the expected ruthenium bisphosphinite complex was not observed. The reaction was carried out in the absence of 1-phenylethane-1,2-diol resulted in the formation of [Ru(η6- cymene)Cl2PPh2Cl] suggests that the diol acts as a reducing agent. To verify the source of hydrogen in the 1-phenylethane-1,2-diol, deuterated diols were prepared. The reactions with the deuterated diols revealed several interesting aspects of the formation of the Ru-PPh2H complex. Chapter 5 “Mechanistic Studies on the Diazo Transfer Reaction” deals with the synthesis of labelled azides and the labelled azidating reagent to probe the mechanism of the diazo transfer reaction. Azides are important precursors used for a variety of chemical transformations including the celebrated Cu(I) catalyzed click reaction. Azides are also used as protecting groups for amines as they can be conveniently reduced to amines. Azidation of amines usually yield azides, with retention of stereochemistry. There is a possibility that the azide formation can occur through the SNi mechanism with retention of configuration where nitrogen in the starting material will not be retained after forming an azide. The reaction was carried out with 13C and 15N labelled L-valine and L-isoleucine to probe this possibility. The resultant labelled azide has 15N retained in its position. This excluded the SNi pathway. To show where the nucleophilic amine group is attacking the azide, labelled imidazole-1¬sulfonyl azide was synthesized from NaN215N. Reactions were carried out with L-valine (labelled and unlabelled) in the presence of a metal catalyst and with unlabelled L-valine in the absence of catalyst. These results confirm the postulated pathways described in the literature.

The binding of molecular hydrogen to a metal center leads to the elongation of the H−H bond and subsequently to its cleavage along the reaction coordinate for the oxidative addition of H2. There has been considerable interest in the study of the activation of dihydrogen and map out the reaction coordinate for the homolysis of H2 on a metal center. A large number of H2 complexes reported to date possess H−H distances ranging from 0.8 to 1.0 Å. A relatively fewer examples of elongated dihydrogen complexes wherein the H−H distances fall in the range of 1.0 to 1.5 Å, are known. Study of the elongated dihydrogen complexes is of great significance because of its relevance in important catalytic processes such as hydrogenation, hydrogenolysis, and hydroformylation. Objectives The objectives of this work are as follows: (a) Synthesis and characterization of elongated dihydrogen complexes with chelating phosphine coligands by varying the electron donor ability. (b) Trap the various intermediate states in the process of oxidative addition of H2 to a metal center. (c) Map the reaction coordinate for the oxidative addition for the oxidative addition of H2 to a metal center. Results We have synthesized and characterized two new elongated dihydrogen complexes cis-[Ir(H)(η2-S2CH)(η2-H2)(PR3)2][BF4] (PR3 = PCy3, PPh3) wherein hydrogen atom undergoes site exchange between the H2 and the hydride sites. The dynamics of the exchange was studied using NMR spectroscopy. In addition, a series of ruthenium dihydrogen complexes of the type trans-[Ru(Cl)(η2-H2)(PP)][BF4] (PP = 1,2- Synopsis bis(diarylphosphino)ethane) has been synthesized and characterized wherein the aryl group is a benzyl moiety with a substituent (p-fluoro, H, m-methyl, p-methyl, p-isopropyl); in this series of complexes, a small increment in the electron donor ability (decrease in Hammett substituent constants) of the chelating phosphine ligand resulted in an elongation of the H−H bond by a small, yet significant amount. We also synthesized a series of 16-electron dicationic dihydrogen complexes bearing elongated dihydrogen ligand. In addition, we prepared a series of dihydrogen complexes of the type [RuCp/Cp*(PP)(η2-H2)][OTf] (PP = 1,2-bis(diarylphosphino)ethane, 1,2-bis(diarylphosphino)methane, 1,2-bis(dialkylphosphino)methane) bearing elongated H2 ligand (dHH = 1.0 to 1.17 Å); in this series of complexes as well, we found that the H−H bond distances increased as the donor ability of the chelating phosphines increased in small increments, along the reaction coordinate for the oxidative addition of H2 to a metal center. This investigation therefore, has established a very nice correlation between the H−H bond lengths and the Hammett substitutent constants (donor properties) resulting in the construction of dihydrogen complexes along the reaction coordinate for the oxidative addition of H2 to a metal center.