A Reliable Quantum-Chemical Protocol for the Characterization of Organic Mixed-Valence Compounds

Citations Over TimeTop 10% of 2009 papers

Abstract

Structures, dipole moments, electron-transfer barriers, and spin density distributions of a series of mixed-valent bistriarylamin radical cations have been studied systematically by hybrid density functional methods with variable exact-exchange admixture combined with a continuum solvent model. The chosen systems differ in their bridging units and are all relatively close, from both sides, to the class II/III borderline of the Robin-Day classification of mixed-valence systems. Solvent effects are found to have a dramatic influence on the localized vs delocalized character of these cations. While gas-phase calculations or computations in a nonpolar solvent place all systems on the delocalized class III side, a more polar solvent like acetonitrile enables observation of symmetry breaking and charge localization with moderate exact-exchange admixtures in a hybrid functional for the systems on the class II side (with diphenylbutadiyne and diphenylethyne bridges). In contrast, the cations with the shortest bridges (phenylene, biphenylene) are characterized as class III. The comparison of computed intervalence charge-transfer excitation frequencies with experiment confirms the system with the diphenylbutadiyne bridge, and probably the system with the diphenylethyne bridge, to be class II, whereas in the dichloromethane solvent employed for spectroscopic measurements, the two other systems are on the class III side. Nonstandard hybrid density functional calculations with 35% Hartree-Fock-like exchange combined with continuum solvent models are suggested as a practical protocol for the quantum-chemical characterization of organic mixed-valence systems. This approach should allow closer examinations and provides a basis for the evaluation of other computational methods.

Related Papers

• → Mechanism of One-Pot Stereoselective Assembly of Spiroketal Derivatives from Cyclohexanone and Phenylacetylene in KOH/DMSO: a Quantum Chemical Study(2023)5 cited
• → Ab initio quantum-chemical study of the unimolecular pyrolysis mechanisms of acetic acid(1986)32 cited
• → A method and program for mass quantum chemical calculations of protein—ligand docking complexes(2008)4 cited
• → A quantum chemical investigation of CO, NF, SO, CF2 and their combination products(1982)4 cited
• → A quantum chemical investigation of CO, NF, SO, CF2 and their combination products(1982)4 cited