Academic literature on the topic 'Meisenheimer complexes: Density functional theory'

A particular emphasis of this thesis has been to provide insight into the underlying stability of these complexes and hence interpret experimental data, and to establish the development of solvation shell structure and its effect on reactivity and excited states. Energy decomposition analysis, fragment analysis and charge analysis has been used throughout to provide deeper insight into the nature of the bonding in these complexes. This has also been used successfully to explain observed preferential stability and dissociative loss products.

Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xxxi, 309 p.; also includes graphics Includes bibliographical references. Available online via OhioLINK's ETD Center

Paddlewheel complexes are molecules in which two interacting metal atoms are bridged by four chelating ligands. This class of complexes has a large range of electronic variability while keeping a rigid geometric structure. This variability has led to their use as catalysts, strong reductants, anti-tumor agents, and electron transfer agents. This dissertation examines the effects of changing both the dimetal core and the surrounding ligands on the electronic structure properties of the paddlewheel complexes. Examination of Bi₂(O₂CCF₃)₄, a p-orbital dimetal paddlewheel complex, provided a way to probe the orbitals that are important in metal-ligand σ bonding. The b(1g) and b(2u) ligand orbitals of Bi₂(O₂CCF₃)₄ have no dimetal orbital counterpart, unlike the case of the more familiar d-orbital dimetal paddlewheel complexes such as Mo₂(O₂CCF₃)₄. This had the effect of destabilizing these ligand orbitals compared to d-orbital paddlewheel complexes. The ligand a1g orbital in Bi₂(O₂CCF₃)₄ was also destabilized due to nodal differences in the dimetal σ orbital. The unusual coincidence of Mo-Mo σ and π ionization bands is due to a greater amount of ligand character in the Mo-Mo σ orbital compared to its ditungsten analogue, which has separate ionization bands for the σ and π bonds. A series of p-substituted dimolybdenum tetrabenzoate complexes was synthesized and studied by photoelectron spectroscopy in order to further examine the delocalization of electron density from the metals to the ligands in these complexes. A 0.89 eV shift in the δ ionization band was observed from Mo₂(O₂CPh-p-OMe) ₄ and Mo₂(O₂CPh-p-CF₃)₄. Overlap effects are the major factor causing the shift in the δ bond ionization, as the calculated charges on the molybdenum and oxygen atoms did not vary significantly on change of substituent. Molybdenum and tungsten guanidinate paddlewheel complexes have promise as good reducing agents due to their extremely low ionization energies. The solubility of the complexes poses a problem for their widespread adoption for use as reducing agents. Alkyl substituents were added to the complexes to increase their solubility. W₂(TEhpp)₄ was observed to have the lowest ionization energy at 3.71 eV (vertical ionization) and 3.40 eV (onset ionization) of any molecule yet prepared.

A combination of theoretical chemistry and “action” spectroscopy has become the most used tool for the exploration of gas-phase molecular ions. In this study, density functional theory (DFT) calculations were used to test the validity of conclusions drawn from the results of a matrix-isolation infrared (MI-IR) experiment and develop a modeling method that could be used for metal-coordinating chlorate ion pairs. That modeling method was then used in comparison with experimental infrared multiple photon dissociation (IRMPD) spectroscopy to determine the structures of metal-chlorate anions. In addition to structural information, the effect of the modeling method on spectral correlation was also investigated.<br>Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry