Modeling of charge-transfer transitions and excited states in d6 transition metal complexes by DFT techniques
2006; Elsevier BV; Volume: 251; Issue: 3-4 Linguagem: Inglês
10.1016/j.ccr.2006.05.021
ISSN1873-3840
AutoresAntonı́n Vlček, Stanislav Záliš,
Tópico(s)Free Radicals and Antioxidants
ResumoThe state of art of the DFT description of charge-transfer electronic excited states of (mostly) d6 transition metal complexes is presented and discussed. A brief theoretical background places DFT amongst quantum-chemical techniques and discusses the approximations involved. The time-dependent DFT (TD-DFT) treatment of electronic transitions is introduced, with emphasis on the challenges presented by long-range charge separation. Various ways how to characterize excited states in chemically relevant terms are discussed. Several detailed case studies demonstrate how DFT describes charge-transfer excited states of ReI or RuII carbonyl-diimine complexes and interprets their photophysics and photochemistry. This "tutorial" section is followed by an overview of DFT and TD-DFT applications to electronic spectroscopy and excited-state properties of metal carbonyls, strongly emissive organometallics, RuII photosensitizers, luminescent "light-switches" and isonitrile complexes of ReI and RuII. Effects of the computational procedure on the quality of the results and the type of information obtained are emphasized. It follows that the most accurate charge-transfer transition energies and descriptions of excited states of low-valent d6 metal complexes are obtained when using hybrid functionals and calculating the molecule in the actual solvent. A rather delocalized picture of charge-transfer states of these complexes emerges, whereby the electron density is excited from the metal atom and part of its coordination sphere to the electron-accepting ligand.
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