Class II mixed-valenceb imetallic complexes {[Cp'(PP)M]CCÀCN[M'(PP)'Cp']} 2 + (M, M' = Ru, Fe;P P = dppe, (PPh 3 ) 2 ;C p ' = Cp*, Cp) exist as conformational ensembles in fluid solution, with ap opulationo fs tructures ranging from cis-t otrans-like geometries.E ach 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,g iving complexb and envelopes in the NIR absorption spectrum,w hich prevent any meaningful attempta t analysis of the band shape. However,D FT and time-dependent (TD)DFT calculations with dispersion-corrected global-hybrid( BLYP35-D3) or local hybrid (lh-SsirPW92-D3) functionals on as malln umber of optimised structures chosen to sample the ground state potentiale nergy hypersurfaces of each of these complexes has proven sufficient to explain the majorf eatures of the electronic spectra. Although modesti n termso fc omputational expense, this approachp rovides a more accurated escription of the underlying molecular electronics tructure than would be possible through analysiso f the IVCT band by using the static point-charge model of Marcus-Hush theory and derivatives, or TDDFT calculations from as ingle (global)m inimum energy geometry.[a] S.Supporting information and the ORCID identification number(s) for the author(s) of this articlecan be found under: https://doi.

The spectroelectrochemically generated infrared (IR) and near-infrared spectra of the homo-bimetallic, hexa-1,3,5-triyn-1,6-diyl-bridged complex cations [{Cp*­(dppe)­M}­(μ-CCC≡CCC)­{M­(dppe)­Cp*}]+ (M = Fe, [1]+; Ru, [2]+) have been analyzed using density functional theory calculations based on global (BLYP35) and local (LH20t) hybrid functionals. The differences in the number of IR active ν­(CCCCCC) modes in these complexes are attributed to the distinct electronic localization of the Fe­(II)–Fe­(III) mixed-valence cation [1]+ on the IR timescale, as opposed to the delocalized electronic character of [2]+.

Infra-red spectroelectrochemical studies of [{Cp′(CO)xM′}(μ-CCC₆H₄CC){M(PP)Cp′}]ⁿ⁺ [n = 0, 1] illustrate limited ground-state interactions in these donor–acceptor compounds and the localised nature of the one-electron redox processes.

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