Dissertations / Theses on the topic 'Cyclometallates'

Within this thesis, research related to the synthesis of Pt(II) and Pt(IV) cyclometallated complexes involving both aryl and alkyl C-H activation is discussed. The introduction reviews literature relevant to C-H activation, cyclometallation and reductive elimination, both historic and current. Four pyridine based pro-ligands, all with a 4-fluorophenyl substituent and a varying alkyl substituent, were synthesised in order to study both aryl and alkyl C-H activation. Initial reactions with K2PtCl4 led to the cyclometallation of the phenyl ring via a reversible aryl C-H activation, which then resulted in a variety of Pt(II) complexes by the addition of different co-ligands. Oxidation of these Pt(II) species gave Pt(IV) complexes, which subsequently underwent isomerisation to give the thermodynamic product. For the DMSO derivatives this was shown to occur via five coordinate complexes stabilised by agostic interactions with the alkyl chain and resulted in the first crystallographically characterised oxygen bound DMSO Pt(IV) complexes. Pt(II) and Pt(IV) sp2 cyclometallated complexes, each with an sp3 agostic interaction, were isolated and characterised when using the more sterically demanding tbutyl derivative of the pro-ligand. Subsequent alkyl C-H activation of the tbutyl group was observed via an intra-molecular transcyclometallation reaction to give complexes with an sp3 cyclometallation. From these species a series of complexes with a C(sp2)^N^C(sp3) tridentate ligand were also synthesised. It was also noted that a reversible rollover reaction of the Pt(II) agostic complex occurred in DMSO solvent by exchanging the C(sp2)^N cyclometallation for a C(sp2)^C(sp2) cyclometallation via decyclometallation, rotation about the central C-C bond and subsequent C-H activation. Reductive elimination of a chloride ligand with both sp2 and sp3 cyclometallated carbons occurred to give functionalised phenyl rings and tbutyl groups, respectively. Steric interactions were shown to play a major role in these reactions.

This thesis describes the synthesis and reactivity of cyclometallated complexes containing nitrogen donor ligands.;Chapter One introduces the general chemistry of cyclometallated complexes containing C,N-bidentate ligands, then describes the mechanism of cyclometallated complexes. This is followed by an overview of the applications of cyclometallated complexes.;Chapter Two provides an introduction to hemilability and reviews the synthesis of cyclopalladated complexes containing C,N,X tridentate ligands (X= N, S, O). The synthesis of new cyclopalladated imines containing oxygen-functionalised tethers is described. Coordination of the oxygen is shown to depend on i) the nature of the oxygen donor, ether, alcohol or phenol. ii) the length of the linker. iii) whether the complexes are neutral or cationic.;Chapter Three establishes the scope of acetate-assisted C-H activation for the synthesis of arene ruthenium and Cp*M (M = Ir, Rh) half-sandwich cyclometallated complexes with nitrogen-donor ligands viz. imine, amine, oxadoline and pyridine and with P(OPh)3. The method can activate sp2 C-H bonds of phenyl, pyrrole and thiophene, and one example of an sp3 C-H bond. The method also allows N-H activation of a pyrrole-imine. Preliminary investigations of the mechanism are also described.;Chapter Four reports the reactivity of the cyclometallated half-sandwich complexes (synthesised in chapter three). Alkenes and CO provide simple substitution products. Alkynes are shown to insert regioselectivity into the M-C bond. In some cases subsequent C-C or C-N bond formation occurs to form carbocyclic or heterocyclic products. With PhC-CH, insertion of two molecules can occur to give novel products. Throughout the thesis X-ray crystallography has been used to verify or identify some of the products (>40 structures).

New series of substituted Ir(ppy)3 derivatives incorporating various vinyl-aryl systems with electron-donating groups on their pyridyl rings or donor/acceptor groups on their phenyl rings were synthesized using the so-called technique “chemistry on the complex”. These complexes are luminescent with emission wavelength that is tuned by introducing stronger donating groups or extending the π-system. These complexes present strong NLO properties controlled by the charge transfer transitions (ILCT and MLCT) induced by donor-acceptor interaction within the complex. We have developed the first example of palladium-catalyzed direct arylation of metallated thiophenes. The arylated derivatives of tris-cyclometallated Ir(thpy)3 and thienyl containing bis-cyclometalated complexes were prepared. The latter were arylated at their thienyl ring located either on the cyclometallated ligand of Ir(thpy)2(acac) and Ir(tbth)2(acac) or on the ancillary ligand of Ir(ppy)2(tta). The resulting complexes present interesting luminescence properties originating from LC 3(π-π*) for complexes with thienyl ring on their C^N ligands while Ir(ppy)2(tta) derivatives emit from excited state based on the ancillary ligand. Preliminary results of the synthesis of iridium platinum tetrametallated complexes Ir-Pt3 were reported. A complex having Ir(ppy)3 core and three (N^N^C)Pt-acetylide fragments was prepared. At room temperature, it shows an emission originating from the platinum fragments. Attempts were made to prepare a more rigid Ir-Pt3 complex based on Ir(thpy)3 core and three (N^N^C)Pt fragments. The complex was successfully prepared; however, its purification was not finished<br>Une nouvelle série de complexes de type Ir(ppy)3 fonctionnalisés par divers vinyle-aryles substitués, soient par des groupements électro-donneurs sur la noyau pyridyle, soient par des groupements donneurs ou accepteurs sur la noyau phényle, ont été synthétisés en utilisant la technique dite de “chimie sur le complexe”. Ces complexes sont luminescents avec une longueur d'onde qui peut être déplacée en introduisant un groupement fortement donneur ou bien en allongeant le système π. Ils présentent de fortes activités en optique non linéaire quadratique qui sont contrôlées par les transitions de transfert de charge (ILCT et MLCT). Nous avons développé le premier exemple d'arylation directe de thiophènes métallés catalysée par le palladium. Les dérivés arylés des complexes Ir(thpy)3 et bis-cyclométallés ont été synthétisés. Les complexes bis-cyclométallés sont arylés au niveau du cycle thiényle situé sur le ligand cyclométallés de Ir(thpy)2(acac) et Ir(tbth)2(acac), ou sur le ligand ancillaire de Ir(ppy)2(tta). Les complexes qui en résultent sont luminescents provenant d’un état excité émissif LC 3(π-π*) pour les complexes avec le thiényle sur les ligands C^N, tandis que les dérivés Ir(ppy)2(tta) émettent à partir de l'état excité centré sur les ligands ancillaires. Les résultats préliminaires sur la synthèse de complexes tétramétallés Ir-Pt3 sont également décrits. Un complexe ayant un cœur Ir(ppy)3 et trois fragments (N^N^C)Pt-acétylure liés a ainsi été préparé. Ce complexe montre une émission provenant des entités platine. Les premiers essais concernant la synthèse d’un complexe plus rigide basé sur un cœur Ir(thpy)3 et trois fragments (N^N^C)Pt sont également décrits

Two stable diastereomeric atropisomers of a cyclometallated iridium complex containing a pyrene functionalized pyridineimine ligand have been isolated. These are the first fully characterized examples of metal containing atropisomers in which the rotational axis is not between two chelating atoms. The atropisomers can be converted thermally via a rocking motion of the pyrene moiety. A new mechanism for enhanced phosphorescence emission in the solid state (EPESS) in cyclometallated Ir complexes with the general formula [Ir(C^N)₂(N^O)] involving distortion of the six-membered chelate ring of the ancillary ligand is proposed. Photophysical and computational studies show that neither π-stacking nor restricted rotation cause the observed EPESS in these complexes and that ligand distortions in the triplet excited state are responsible for EPESS. Bis-cyclometallated Ir(III) complexes with the general formula Ir(ppz)₂(N^XPyrene) where X = N or O are shown. Modifications on the ancillary ligand containing pyrene drastically affect the emission lifetimes observed (2 μs to 104 μs). Extended emission lifetimes in these complexes compared to model complexes result from reversible electronic energy transfer or the observation of pyrene (³LC) phosphorescence. A combination of steady state and time-resolved spectroscopic techniques are used to observe reversible electronic energy transfer between the cyclometallated iridium core and the pyrene moiety in the complexes [Ir(ppz)₂(N^NPyrene)][PF₆]. Replacing the N^NPyrene ligand with an N^OPyrene ligand results in long-lived pyrene phosphorescence. Reversible electronic energy transfer as well as 3pyrene emission is observed and characterized in a PMMA film.<br>Science, Faculty of<br>Chemistry, Department of<br>Graduate

The dinuclear cyclometallated gold(I) complex [Au2(μ-2-C6F4PPh2)2] was prepared in high yield from the reaction of 2-LiC6F4PPh2 with either [AuBr(AsPh3)] or [AuCl(tht)], and from the reaction of 2-Me3SnC6F4PPh2 with [AuCl(tht)]. The digold(I) complex undergoes oxidative addition reactions with halogens to give the metal-metal bonded dihalodigold(II) complexes [Au2IIX2(μ-2-C6F4PPh2)2] (X = Cl, Br, I), which on warming or exposure to light, isomerise to give the heterovalent gold(I)-gold(III) species [XAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX] containing a four-membered cyclometallated ring on a gold(III) centre. Unlike its protio analogue, [Au2(μ-2-C6F4PPh2)2] did not undergo oxidative addition of methyl iodide or dibenzoyl peroxide. The dihalodigold(II) [Au2IIX2(μ-2-C6F4PPh2)2] and gold(I)-gold(III) compounds [XAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX] (X = Cl, Br) are further oxidised by halogens to give the digold(III) species [Au2X4(μ-2-C6F4PPh2)2] and [X3Au(μ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuX], respectively. The complexes [Au2X4(μ-2-C6F4PPh2)2] are reduced to the dihalodigold(II) complexes in the presence of one equivalent of zinc powder; further addition of zinc gave the parent digold(I) dimer. Treatment of [Au2IICl2(μ-2-C6F4PPh2)2] and [ClAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuCl] with an excess of silver nitrate, benzoate, acetate, trifluoroacetate or triflate gave the corresponding oxyanion complexes. Slow crystallisation of the di(benzoato)digold(II) complex from dichloromethane and methanol gave the parent digold(I) complex derived by reductive elimination. The di(triflato)digold(II) complex behaved similarly, although in this case the novel gold(I) tetramer [Au4(μ-2-C6F4PPh2)4] was formed together with the dimer. Two closely related gold complexes containing the chelating κ2(C,O) phosphine oxide ligand, 2-C6F4P(O)PPh2, were isolated from the reaction of [ClAu(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)AuCl] with an excess of silver nitrate. The reaction of [Au2IICl2(μ-2-C6F4PPh2)2] with two equivalents of potassium trifluoroethoxide failed to give the corresponding digold(II) bis(alkoxo) complex; instead, reduction took place to form the digold(I) dimer [Au2(μ-2-C6F4PPh2)2]. Treatment of a solution of the di(benzoato)digold(II) complex with C6F5Li gave the pentafluorophenyl complex [Au2(C6F5)2(μ-2-C6F4PPh2)2] which, when heated in toluene, rearranged to the gold(I)-gold(III) complex [(C6F5)Au(µ-2-C6F4PPh2)(κ2-2-C6F4PPh2)Au(C6F5)], analogous to the behaviour of the dihalodigold(II) complexes. The heterovalent, gold(I)-gold(III) dimethyl compound [Au2I,III(CH3)2(μ-2-C6F4PPh2)2] was obtained from the reaction of the di(benzoato)digold(II) complex with dimethylzinc. This compound is structurally similar to its tetraprotio analogue. The cycloaurated dinuclear gold complexes [Au2(μ-C6H3-n-F-2-PPh2)2] (n = 5, 6) were made similarly to the 2-C6F4PPh2 analogue from the appropriate lithium or tin reagents, though in some cases the dimers were formed in admixture with the corresponding gold(I) tetramers. Like their tetrafluoro analogues, the 6-fluoro complexes [Au2X2(μ-C6H3-6-F-2-PPh2)2] (X = Cl, Br, I) rearrange on heating to give the heterovalent gold(I)-gold(III) species [XAu(µ-C6H3-6-F-2-PPh2)(κ2-C6H3-6-F-2-PPh2)AuX]. Thus, the presence of a fluorine atom in place of hydrogen in the 6-position of the bridging aryl group is sufficient to stop the isomerisation of the digold(II) complexes [Au2X2(μ-2-C6H4PPh2)2] at the gold(I)-gold(III) stage and to prevent subsequent C-C coupling of the aryl groups at the gold(III) centre. In contrast, the dihalodigold(II) complexes containing the 5-fluoro substituted ligand undergo reductive elimination and coupling of the metallated aryl groups to give the digold(I) biphenyldiyl complexes [Au2X2(2,2'-Ph2P-5-FC6H3C6H3-5-F-PPh2)] (X = Cl, Br, I). The described complexes were characterised using 1H NMR, 31P NMR, 19F NMR spectroscopy, elemental analysis, mass spectroscopy, IR spectroscopy, X-ray diffraction and 197Au Mössbauer spectroscopy.

The luminescence properties of cyclometallated iridium(III) complexes render them of interest, for example, as phosphorescent dopants in organic light-emitting devices (OLEDs), as photoactive units in solar energy conversion, and as biosensors. The vast majority comprise three bidentate ligands, archetypal examples being Ir(ppy)3 and [Ir(ppy)2(bpy)]+ (ppy = 2-phenylpyridine; bpy = 2,2'- bipyridine). The work described here explores the chemistry of iridium(III) complexes that contain a terdentate cyclometallating ligand. Most of the complexes studied have the general formula Ir(N^C^N)(N^C)X, where N^C^N represents a terdentate ligand based on 1,3-di(2-pyridyl)benzene; N^C a bidentate ligand such as ppy; and X is a monodentate ligand such as chloride, cyanide, thiocyanate or an acetylide. The synthetic methodology developed involves reaction of the N^CH^N proligand with iridium(III) chloride to give a dimer of the form [Ir(N^C^N)Cl(-Cl)]2, which is cleaved upon treatment with a bidentate N^CH ligand. The one remaining chloride ligand can then be exchanged for other monodentate ligands through silvercatalysed metathesis. Most of these complexes are highly luminescent, with quantum yields in degassed dichloromethane at room temperature between 0.2 and 0.9. The effect of substituents in both the aryl and pyridyl rings of the terdentate and bidentate ligands has been investigated, together with the influence of X. The emission energy has been shown to vary over a very wide range, from the blue to red regions (max = 456 to 667 nm). The trends have been partially rationalised using time-dependent density functional theory and cyclic voltammetry. Some complexes have been incorporated into multi-layer OLEDs that display unusually high efficiency, particularly for the red-emitting devices. Selected rhodium(III) analogues have been prepared, together with related iridium(III) complexes incorporating bidentate N^N (bpy) ligands. A preliminary investigation into the utility of these complexes for the construction of multimetallic assemblies has been made, through the introduction of bridging ligands into position X.

A series of cyclometallated platinum and palladium(lI) complexes based on the N'C'N coordinating terdentate ligand 1,3-di(2-pyridyl)benzene, HL1, have shown that cyclometalation at C2 of the central ring affords many advantages to square-planar d8-metal complexes. The cyclometalating bond is notably shorter than that observed in many related cyclometallated complexes, e.g. 6phenyl- 2,2'-bipyridine platinum/palladium(lI) chloride and 2-phenylpyridine derivatives. The luminescent properties of the complexes reported herein have been investigated. All complexes are intensely luminescent, in their own right, with quantum yields of luminescence significantly higher than those reported for :related complexes. In the solid-state and at high concentrations, intermolecular interactions create new emissive species, such as self-quenching accompanied 'by excimeric emission observed in solution, Aem =: 700 nm, and multi-centred excited-states in solid samples, Aem =610-700 nm. Modification of both N'C'N and ancillary ligands is shown to manipulate the electronic properties of the d8 _ . metal complexes. Excited-state emission energies have been tuned from 469 nm (blue), L26ptCI, to 588 nm (red), L16ptCI, in the platinum(lI) complexes, and from 466 nm (blue), L1pdCI, to 530 nm (orange), L16pdCI, in the palladium comp!exes. Incorporation of steric incumberance into the ligands can attenuate the excimer emission compared to L1PtCI. Electron-rich pendant ligands encourage the accessibility of charge-transfer excited-states, which adds to the diversity of the photophysical properties, but when coupled with functional groups can give rise to potential in sensory applications. The high quantum yields and special oxygen sensitivity of the platinum complexes have allowed their incorporation into optoelectronic devices. The palladium complexes are of particular interest owing to the limited attention previously paid to palladium complexes as emissive species, particularly, excimeric behaviour is even rarer. Additionally, the electronic tuning which is manifested in the luminescent properties of these complexes has allowed studies into catalytic behaviour of these complexes, revealing some surprising results relating activity to structure.

Includes abstract.<br>Includes bibliographical references.<br>Ethylene oligomerization reactions catalysed by cyclometallated palladium(II) N-benzylidenebenzylamine complexes were studied theoretically. Density functional theory (DFT) calculations are reported on the interaction of various MAO models with the methylated pre-catalyst. The neutral MAO dissociation process is shown to remain the major interaction that takes place in the Pd/MAO interactions. On the other hand, the formal methyl abstraction process could be also feasible if more energy is provided. Therefore, the relative energies were calculated for intermediates and transition states for both Cossee-type and metallacycle mechanisms.

The present Doctoral Thesis focuses in two main fields: alkyne-dicobaltcarbonyl complexes (PART I) and chiral ferrocene derivatives (PART II). Therefore, the obtained results can be summarized as follow: <br/><br/>1. The methodology designed for the synthesis of enantiomerically pure phosphane-substituted carbonyl complexes of propargyl aldehyde was not successful. The steric hindrance at position C-4 of the oxazolidin-2-one and oxazolidin-2-thione appears to difficult the removal of the auxiliary in the corresponding N-(2-alkynoyl) dicobaltcarbonyl complexes.<br/><br/>2. The general catalytic behavior of octacarbonyl dicobalt in the opening of cyclic ethers, such as tetrahydrofuran, by acid chlorides, leading to 4-chlorobutyl esters, has been demonstrated.<br/><br/>3. A pathway to access 1'-substituted and 2-substituted beta-ferrocenyl beta-amino alcohols has been developed. In this way, the synthesis with a high level of enantiomeric purity of (S)-2-amino-2-(1'-methyl)ferrocenylethanol, (pS,R)-2-amino-2-(1-trimethylsilyl)-ferrocenyl ethanol and (pR,R)-2-amino-2-(1-methyl) ferrocenyl ethanol has been achieved via their corresponding diols.<br/><br/>4. A general methodology which gives easy access to mono and disubstituted (1,1'- and 1,2-) 4-ferrocenyl-1,3-oxazolines has been developed.<br/><br/>5. A new type of interannular cyclopalladation of ferrocene has been established. The reaction seems to be quite general for 4-ferrocenyl-1,3-oxazolines with different degrees of substitution of the ferrocene moiety, provided that the C2-oxazoline substituent bears no á-hydrogens. The reaction of 4-ferrocenyl-1,3-oxazolines with palladium acetate in benzene leads to the formation of C2-symmetric complexes with two ferrocene moieties cycloplalladated at the 1' position, connected by a central palladium and four acetate bridges. When the cyclopalladation is performed by disodium tetrachloropalladate, a similar complex, but with two chloride bridges, is obtained. The 3-palladium acetate complexes can be converted into the 2-palladium chloride ones by treatment with lithium chloride in methanol. The structures of both types of complexes have been thoroughly studied by spectroscopy and by X-ray diffraction.<br/><br/>6. Cyclic voltammetric studies of these novel interannular palladacycles have been performed.<br/><br/>7. The µ-chloro bridged dipalladium complex (S)-84 undergoes bridge-splitting with triphenylphosphine leading in nearly quantitative yield to the monomer complex (S)-95. On the other hand, the reaction of (S)-84 with iodine affords 1'-iodo-2-tert-butyl-4-ferrocenyl oxazoline (S)-100. This compound has been converted into 1'-phenyl-2-tert-butyl-4-ferrocenyloxazoline (S)-101 by Suzuki coupling with phenylboronic acid. Finally, (S)-84 leads in good yields to the 1'-diphenylphosphinyl- and 1'-diphenylphosphinothioyl ferrocenes (S)-103 and (S)-104. <br/><br/>8. Interannularly palladated 4-ferrocenyl-1,3-oxazolines behave as active promoters of the Heck olefination, allowing the reaction to be performed at lower temperatures than previously known CN-palladacycle pre-catalysts derived from ferrocene. In the reaction medium, the olefin partner couples with the 1'-position of the ferrocene, leading to the formation of soluble palladium(0) catalytic species. For the first time, the ligand-olefin adduct has been isolated and unequivocally characterized, and further evidence favoring the involvement of a Pd(0)/Pd(II) catalytic cycle has been obtained.<br/><br/>9. The new interannular cyclopalladated ferrocenes have been found to be good catalysts for the asymmetric aza-Claisen rearrangement. Thus, the rearrangement of (E)-cinnamyl N-aryl benzimidates 129-131 takes place with moderate yields (40-49%) and with excellent enantioselectivity (up to 90% ee of the rearranged amide 138). Interestingly enough, the acetate-bridged 3Pd complexes lead to the (S) enantiomer of the rearranged allylic amide, while the chloride bridged 2Pd complexes (from the same (S)-enantiomer of the chiral 4-ferrocenyl-1,3-oxazoline) lead to the opposite (R) enantiomer of the amide.<br/><br/>10. New and outstanding catalysts for the aza-Claisen rearrangement of (E)- and (Z)-allylic trichloroacetimidates have been found. The rearrangement of both (E)- and (Z)-hexenyl trichloroacetimidates, performed in chloroform solution at 38oC with a molar 5% of the chloride bridged 1'-cyclopalladated complex, takes place with quantitative conversion and with outstanding enantioselectivity (>98% ee), according to 1H-NMR and HPLC analyses. Intriguingly, both diastereomers of the starting imidate lead to the same enantiomer (S) of the rearranged amide 142.

The photoluminescence properties of cyclometallated second and third row transition metal complexes make them potential candidates for use in a range of applications such as triplet harvesting agents in OLEDS, as photosensitizers, and in solar cells. Also, the strong luminescence of these complexes gives them much potential for use in chemosensing applications and as bioimaging agents. This final topic is an area of increasing study as a result of the diverse and tuneable excited states of such molecules, and their advantages over conventional organic emitters such as reduced photobleaching and long luminescence lifetimes allowing time-resolved imaging to be performed. The synthesis of cyclometallated complexes of the type [Pt(N^C^N)Cl], [Ir(N^C)2(L)Cl], and [Ir(N^C^N)(N^X)Cl]n+ (where N^C^N and N^C are terdentate and bidentate cyclometallating aromatic ligands; L = monodentate pyridine ligand; X = heterocyclic N or cyclometallated aryl C; n = 0,1) is described and their reactions with thiolates are explored with the aim of producing new classes of thiol sensors. Thus, novel monometallic complexes of the type [Pt(N^C^N)(thiolate)] and [Ir(N^C^N)(N^C)(thiolate)] are reported as well as a novel series of dimers with the general structure [Ir(N^C)2(μ- thiolate)]2 and one example of a [Ir(N^C^N)(μ-thiolate)(thiolate)]2 dimer. The effect of the introduction of a thiolate ligand on the excited states of the Pt(N^C^N) complexes is also described. In addition, a series of luminescent compounds based on the dansyl group or iridium complexes are reported for use as bioimaging agents and their utility in cellular assays has been investigated. These probes incorporate molecular structures inspired by the ability of small molecules to mimic the activity of certain redox active proteins and hence have the potential to engage in disulfide exchange processes in vivo. These compounds have been shown to display acceptable uptake into cells without excessive cytotoxicity and have been used to obtain fluorescence microscopy images of live CHO cells.

Afin d'observer un transfert d'electron optique ou un transfert d'energie dans des systemes multimetalliques, nous avons prepare deux series de complexes dans lesquelles la distance centre a centre peut etre modulee. Les ligands pontants sont des ligands biscyclometallants, synthetises par des reactions de couplage de type suzuki ou stille. Dans les complexes a valence mixte ruthenium(ii)-ruthenium(iii), l'element de matrice de couplage electronique vab, ainsi que la stabilite des especes a valence mixte, ont ete determines. Le couplage electronique reste important meme a longue distance. Nous avons aussi observe un couplage electronique plus important pour un isomere de position para par rapport a son isomere meta. L'etude photophysique de la serie des complexes ruthenium(ii)-osmium(ii), a montre un transfert d'energie du ruthenium vers l'osmium. L'efficacite ainsi que la vitesse du transfert d'energie diminuent avec la distance intermetallique. Les proprietes des complexes prepares ont ete comparees a celles des complexes isostructuraux a ligands pontants bisterpyridine. La cyclometallation provoque des changements importants sur les proprietes electrochimiques et de luminescence des complexes, et donc sur le transfert d'electron ou d'energie

Four structural isomers of platinum(II) complexes with C-deprotonated R-C^N^N-R’ cyclometallated ligands (R-C^N^N-R’ = -extended 6-aryl-2,2’-bipyridine derivatives containing 2-naphthyl, 3-isoquinolinyl, 1-isoquinolinyl or 2-quinolinyl moieties) have been synthesized with their photophysical properties investigated. The one bearing a 3-isoquinolinyl moiety shows the highest emission quantum yield among the four and hence has been extensively modified to give a series of complexes with different ancillary ligands (chloride, iodide, phenoxide, or acetylide). Most of these complexes show vibronic emission (max = 515–644 nm) with high emission quantum yield (up to unity) in degassed CH2Cl2; one of them has been used for OLED fabrication and shows a maximum EQE of 8.15 % with current efficiency of 25 cd A–1. The photocatalytic properties of these derivative complexes for oxidative tertiary amine functionalization have also been examined. Several highly robust and emissive platinum(II) complexes supported by two types of tetradentate O^N^C^N ligand systems (Φem up to 0.99; Td up to 520 ℃) have been synthesized and show different emission energies (λmax = 482–561 nm). Most of them exhibit excimeric emission in solution state at room temperature which are dependent on the modifications on the tetradentate O^N^C^N ligands. DFT/TDDFT calculations reveal that the metal complex showing the most intense excimeric emission possesses an excimeric excited state with a localized structure, which is unusual for these classes of platinum(II) complexes. Based on this finding, WOLED (ηL(max) = 71.0 cd/A, ηp(max) = 55.8 lm/W, ηExt = 16.5 %, CIE = 0.33, 0.42, CRI = 77) and WPLED (ηL(max) = 17.0 cd/A, ηp(max) = 9.1 lm/W, ηExt = 9.7 %, CIE = 0.43, 0.45, CRI = 78) based on this complex have been fabricated with high efficiency achieved. Palladium(II) complexes containing C-deprotonated R-C^N^N-R’ cyclometallated and pentafluorophenylacetylide ligands exhibit phosphorescence in both solid state and fluid solutions at room temperature with some of them exhibiting aggregation-induced emission (AIE). These complexes have been applied as photosensitizers in light-induced oxidative functionalization of secondary and tertiary benzylic amines as well as in light-induced hydrogen production, with a maximum of 175 turnovers for hydrogen produced. Palladium(II) complexes containing two types of tetradentate dianionic O^N^C^N ligand systems (Systems 1 and 2) have been prepared and show constrasting photophyical properties. A full scale time-resolved spectroscopic analysis has been done on some of these complexes and a platinum(II) analogue. These complexes are found to have similar excited state decay pathway( 〖S_1〗^i→〖S_1〗^f→T) with ΦISC of about unity. The emission efficiency of System 2 complexes is superior to that of System 1 complexes, which is ascribed to the suppression of excited state distortion on the basis of the results of DFT calculations. A lower radiative decay rate of System 2 palladium(II) complexes relative to the platinum(II) analogue has been found, which could be due to their lower spin-orbit coupling constant. One of the palladium(II) complexes has been applied in vacuum-deposited OLEDs with maximum current density, power efficiency and EQE of 20.0 cd A^(-1), 13.6 lm W^(-1) and 7.4 % respectively. In addition, applications of these palladium(II) complexes as photosensitizers for oxidation of secondary amines have been examined.<br>published_or_final_version<br>Chemistry<br>Doctoral<br>Doctor of Philosophy

La tesis doctoral se divide en cuatro partes: a) Síntesis de complejos ciclopaladados endocíclicos de cinco eslabones derivados de la (E)-N-benciliden-2-(2',6'-diclorofenil)etanamina, de fórmula [(Pd{C6H4CH=N(CH2)2(2,6-Cl2C6H3)-κC,κN}(μ-X))2] (X = OAc, Cl) y [Pd{C6H4CH=N(CH2)2(2,6-Cl2C6H3)-κC,κN}L(X)] (X = OAc, Cl; L = py-d5, PPh3). Se ha ensayado la reactividad de los correspondientes complejos puente cloruro frente a una gran variedad de bases de Lewis [N,N] y [P,P] rígidas y flexibles {tales como 2,2'-(etilendioxi)bis(etilamina); 1,3-diaminopropan-2-ol; etilendiamina; trans-1,2-bis(difenilfosfino)etileno; 1,2-bis(difenilfosfino)etano; y 4,4'-bipiridina}. b) Preparación de complejos ciclopaladados puente acetato a partir de la doble activación σ(Csp2−H) intramolecular de las diiminas de fórmula (RC6H4CH=NZ)2 [Z = CH2, R = p-Cl, p-MeO, p-NO2, o-Cl; Z = (CH2)2OCH2, R = p-Cl, p-MeO, p-NO2, o-Cl]. Las condiciones de la reacción de ciclopaladación se optimizaron para el sustrato con Z = CH2 y R = p-Cl. La preparación in situ de los derivados dimetalados [{Pd(O2CMe)(py-d5)(RC6H3CH=NZ-κC,κN)}2] reveló la existencia de sistemas menores que se asignan a los complejos iónicos [{Pd(py-d5)(RC6H3CH=NZ-κC,κN)}2(μ-O2CMe)](OAc) (para Z = CH2), [(py-d5)2Pd(μ-L)Pd(OAc)(py-d5)](OAc) {para Z = CH2 y (CH2)2OCH2}, y al correspondiente complejo diciclopaladado bis(tridentado) {para Z = (CH2)2OCH2}. Se constata que la proporción molar de las distintas especies es dependiente de la concentración de la muestra. También se describe la síntesis de los complejos [({Pd(μ-Cl)(RC6H3CH=NZ-κC,κN)}2)n] y [{PdCl(PPh3)(RC6H3CH=NZ-κC,κN)}2]. Adicionalmente, se ensaya la reactividad de algunos derivados diciclometalados puente cloruro frente a bases de Lewis [N,N] y [P,P], que actúan como ligandos bis(monodentados) en la síntesis de metalomacrociclos de fórmula [{(Pd(Cl){4-ClC6H3CH=N(CH2)2OCH2-κC,κN})2(μ-L?L)}n] {L?L = NH2(CH2)2O(CH2)2O(CH2)2NH2, Ph2PCH=CHPPh2}. Con objeto de elucidar la nuclearidad de las especies en solución, se realizan simulaciones de dinámica molecular y cálculos DFT de los sistemas [({Pd(Cl){4-ClC6H3CH=N(CH2)2OCH2-κC,κN}}2{μ-NH2(CH2)2O(CH2)2O(CH2)2NH2-κN:κN'})n] (donde n = 1 y 2). c) Síntesis de nuevos complejos orto-ciclopaladados endo hidrosolubles a partir de la activación directa intramolecular de enlaces C−H de N-bencilidenanilinas con sustituyentes polares o grupos ionizables [de fórmula RPhCH=N(C6H4-4-COOR') (R = H, Cl, p-NMe2, p-NO2; R' = H, Me)]. Se ailaron los derivados monometalados de fórmula [(Pd(μ-O2CMe){RC6H3CH=N(C6H4-4-COOH)-κC,κN})2], que mostraron cierta solubilidad en solución acuosa a pH 10. La adición de un exceso de py-d5 a una suspensión de estos complejos en D2O condujo a los complejos mononucleares zwitteriónicos [Pd(py-d5)2{RC6H3CH=N(C6H4-4-COO)-κC,κN}], solubles en agua. Por otro lado, se prepararon complejos ciclopaladados quelato puente [C,N,O] de fórmula [(Pd(L){μ-RC6H3CH=N(C6H4-4-COO)-κC,κN:κO})2] (L = py, PPh3). El inusual modo de coordinación del ligando metalado tras la desprotonación del grupo carboxilo es responsable de su insolubilidad en agua. También se han preparado complejos ciclopaladados endo de cinco eslabones de fórmula [(Pd{C6H4CH=N(C6H4-4-COOMe)-κC,κN}(μ-X))2] (X = OAc, Cl) y sus derivados [Pd(C?N)L(X)] (X =OAc, Cl; L = py, PPh3). La caracterización de los compuestos [Pd(C?N)(py)X] (X = OAc, Cl) revelaron una mezcla de los estereoisómeros trans-N,N y cis-N,N, cuya relación molar varía en función del disolvente. Sorpresivamente, los complejos [Pd(C?N)(py)X] (X = OAc, Cl) se disuelven en D2O al añadir un exceso de piridina-d5 debido a la formación del compuesto cis-[Pd(C?N)(py-d5)2]X (X = OAc, Cl). Adicionalmente, se incluye un estudio teórico de la estereoquímica de la reacción de escisión de los complejos dinucleares ciclopaladados puente. Los cálculos DFT se plantearon para un sistema modelo de fórmula [Pd(CH=CH−CH=NH)X(L)] (X = OAc, Cl, Br, I; L = py, NH3, PH3, PMe3) con el fin de establecer unas tendencias sobre la estabilidad relativa de ambos isómeros. d) Preparación de heterociclos dibenzo[b,d]-fusionados mediante arilación catalítica directa. La síntesis de los diferentes carbazoles se realizó en dos etapas, tras una aminación Buchwald-Hartwig catalítica para obtener las correspondientes diarilaminas halosustituidas, seguida de una activación C–H catalizada por complejos de paladio.<br>Intramolecular aromatic C−H bond activation is explored in the synthesis of novel endo five-membered ortho-cyclopalladated imine and diimine complexes. The N-donor ligands tested in this reaction were the N-alkyl imine PhCH=N(CH2)2(2,6-Cl2C6H3), the symmetric diimines with the general formula (RC6H4CH=NZ)2 (Z = CH2 or (CH2)2OCH2) in a range of substitution patterns, and the N-benzylideneanilines RC6H4CH=NC6H4-4-COOR' (R' = H or Me). Reactivity studies of the corresponding bridged-cyclopalladated complexes with monodentate Lewis bases, as well as rigid or flexible [N,N] and [P,P] Lewis bases, are also reported. All cyclometallated derivatives were characterised by conventional spectroscopic techniques, elemental analysis, and X-ray diffraction (when possible). In addition, the stereochemistry of a simplified endo five-membered mononuclear cyclopalladated imine model was computationally examined. This report also deals with some aspects of the solution chemistry of doubly cyclopalladated complexes in terms of nuclearity and equilibrium processes. Furthermore, considerable efforts were made to synthesise metallomacrocycles containing one or more dimetallated moieties and bis(monodentate) Lewis bases. Two novel metallomacrocycles were isolated and spectroscopically characterised, although their nuclearity remains unclear. Theoretical calculations were therefore performed in order to gain insight into the nuclearity and conformation of the species present in solution, which showed temperature and solvent-polarity dependence. In an attempt to synthesise new water-soluble cyclopalladated complexes, the strategy of incorporating polar substituents or ionisable functional groups into the N-donor ligand was examined. Hydrosoluble carboxylated palladacyclic species of a zwitterionic nature were obtained in solution in the presence of an excess of pyridine. By contrast, some related cyclometallated derivatives showed unanticipated coordination of the carboxylate group that resulted in the formation of a water-insoluble 16-membered metallomacrocyclic complex. In parallel, an additional route for the preparation of hydrosoluble palladacycles was unexpectedly found. A study was also carried out on the two-pot synthesis of carbazoles from aryl bromides and the appropriate aniline via initial catalytic Buchwald-Hartwig amination followed by palladium-catalysed intramolecular C−H activation.

<p><font face="TimesNewRomanPSMT"> <p align="left">This thesis reports the synthesis of the imine ligands from Schiff base condensation reaction of aldehyde derivatives and equimolar quantities of aniline derivatives. The imine ligands spectrometry.</p> </font></p>

<p>With the advent of well-defined highly active catalysts, olefin metathesis has become a powerful tool for the formation of carbon–carbon double bonds in a variety of settings. However, these traditional catalysts preferentially form the E-alkene product. Recent efforts have yielded several families of Z-selective metathesis catalysts, including a family of Ru complexes with cyclometallated NHC ligands developed in our group. The work in this thesis describes efforts to develop an improved understanding of the catalyst features that govern activity and selectivity in the cyclometallated Ru-based catalysts, as well as to expand the scope of reactivity in these systems.</p> <p>Chapter 1 provides an outline of the key features that govern selectivity in cross metathesis applications.</p> <p>Chapter 2 describes the application of cyclometallated Ru-based catalysts in Z-selective cross metathesis (CM) of allylic-substituted olefins. Efficient CM is demonstrated in the case of acrolein acetals providing a new route to access Z-α,β-unsaturated acetals and aldehydes. For a variety of other allylic-substituted olefins, reactivity was lower but could be correlated with the structure of the catalyst and substrate. The implications of the observed reactivity are discussed and contextualized with regard to reactivity of previous metathesis catalysts.</p> <p>Chapter 3 describes the development of a series of cyclometallated Z-selective metathesis with varying N-aryl groups that allow elucidation of the key catalyst features that govern activity and selectivity in these systems. The synthesis of the catalyst series is described, including several strategies employed to circumvent unexpected side-reactions. The second part of the chapter focuses on the dynamic behavior of the catalysts in solution and studies of an unusual C–H····F–C intramolecular interaction observed in some of these catalysts. Finally, the reactivity of these catalysts in a variety of CM applications are discussed, which allows for development of a refined model of how the N-aryl group affects Z-selectivity and activity in these catalysts systems and how this varies across different classes of substrate.</p>

The objective of this thesis is to examine the photophysical and structural properties of Cu(I) complexes of 2-(2’-pyridyl)benzimidazolyl based ligands and Cu(I), Pd(II) and Pt(II) complexes of 2-(2’-pyridyl)indolyl based ligands, for possible use as phosphorescent emitters in OLEDs. The discovery of the atropisomeric 3,3’-bis(2-(2’-pyridyl)indolyl based ligands led to the examination of C-C coupling reactions and the investigation of the new chiral ligands with transition metal ions. Cu(I) complexes of 2-(2’pyridyl)benzimidazolyl-benzene with varying phosphine ligands were prepared. The structures were studied with X-ray crystallography and NMR. Experimental and computational results established that steric and electronic properties of the phosphine ligands influence the photophysical properties of the Cu(I) complexes. Polynuclear Cu(I) complexes with 2-(2’-pyridyl)benzimidazolyl based ligands and two PPh3 ancillary ligands were synthesized, the photoluminescent and electroluminescent properties were examined. A series of 2-(2’-pyridyl)indolyl based ligands; 2-(2’-pyridyl)indolyl-benzene (pib), 1,4-bis[2-(2’-pyridyl)indolyl]benzene (bib) and 1,3,5-tris[2-(2’-pyridyl)indolyl]benzene) (tib) and the corresponding C-C coupled dimers bis[3,3’(2-(2’-pyridyl)indolyl-benzene)] (bpib), bis[3,3’(1,4-bis[2-(2’-pyridyl)indolyl]benzene (bbib) and bis[3,3’(1,3,5-tris[2-(2’-pyridyl)indolyl]benzene)] (btib) were synthesized in a one-pot reaction with the formation of both C-N and C-C bonds. The photophysical properties of these new molecules were investigated. The dimers display intramolecular exciplex formation. The rotation barrier around the C-C bond in the 3 position of the bis-indole was calculated using DFT which support that bpib is an atropisomeric ligand. Cu(I), Pd(II) and Pt(II) complexes were synthesized with pib and bpib. [Cu(pib)(PPh3)2]+ contains a three-coordinate Cu(I) ion and doesn’t display MLCT but rather 3π-1π phosphorescence. In Pd(pib)(acac) and Pt(pib)(DMSO)Cl the pib ligand forms C,N chelated neutral complexes that display red emission in frozen solution and in solid state. The X-ray crystal structure for [Cu(bpib)2]+ revealed a homo-chiral crystal and for Pd(bpib)Cl2 and Pt(bpib)Cl¬2 show a trans-chelating geometry around the metal centre. Frozen solutions of [Cu(bpib)2]+ and Pd(bpib)Cl2 display MCLT phosphorescence. Finally the atropisomeric ligands bpib and bbib were examined as sensors to determine the enantiomeric excess of Zn(2-bromo-3-methylbutyrate)2 by CD spectroscopy. CD and fluorescent titration experiments verified that these ligands have selective interactions with different Zn(II) carboxylates. DFT computations showed that diastereomeric excess caused by chiral discrimination leads to the CD spectral-response of the atropisomeric ligands toward chiral Zn(II) carboxylates.<br>Thesis (Ph.D, Chemistry) -- Queen's University, 2008-09-25 09:54:21.464