A Spectroscopic and Computationally Minimal Approach to the Analysis of Charge‐Transfer Processes in Conformationally Fluxional Mixed‐Valence and Heterobimetallic Complexes. Issue 37 (5th June 2019)

• Record Type: Journal Article
• Authors: Gückel, Simon; Gluyas, Josef B. G.; Eaves, Samantha G.; Safari, Parvin; Yufit, Dmitry S.; Sobolev, Alexandre N.; Kaupp, Martin; Low, Paul J.
• Is Part Of: Chemistry. Volume 25:Issue 37(2019)
• Page Start: 8837
• Page End: 8853
• Publication Date: 2019-06-05
• Subjects: density functional theory -- intervalence charge transfer -- mixed valence -- organometallic complexes -- spectroelectrochemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201901200
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Class II mixed‐valence bimetallic complexes {[Cp′(PP)M]C≡C−C≡N[M′(PP)′Cp′]} 2+ (M, M′=Ru, Fe; PP=dppe, (PPh3 )2 ; Cp′=Cp*, Cp) exist as conformational ensembles in fluid solution, with a population of structures ranging from cis ‐ to trans ‐like geometries. Each conformer gives rise to its own series of low‐energy intervalence charge‐transfer (IVCT) and local d–d transitions, which overlap in the NIR region, giving complex band envelopes in the NIR absorption spectrum, which prevent any meaningful attempt at analysis of the band shape. However, DFT and time‐dependent (TD)DFT calculations with dispersion‐corrected global‐hybrid (BLYP35‐D3) or local hybrid (lh‐SsirPW92‐D3) functionals on a small number of optimised structures chosen to sample the ground state potential energy hypersurfaces of each of these complexes has proven sufficient to explain the major features of the electronic spectra. Although modest in terms of computational expense, this approach provides a more accurate description of the underlying molecular electronic structure than would be possible through analysis of the IVCT band by using the static point‐charge model of Marcus–Hush theory and derivatives, or TDDFT calculations from a single (global) minimum energy geometry. Abstract : Mapping the landscape : Conformational mixtures of mixed‐valence (MV) complexes were studied by using a combination of NIR spectroscopy and DFT methods. Just three minima chosen to sample the potential energy hypersurface proved sufficient to describe the electronic structures and account for the IVCT band shape.