Premium
The Use of Bridging Ligand Substituents to Bias the Population of Localized and Delocalized Mixed‐Valence Conformers in Solution
Author(s) -
Safari Parvin,
Gückel Simon,
Gluyas Josef B. G.,
Moggach Stephen A.,
Kaupp Martin,
Low Paul J.
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202200926
Subject(s) - delocalized electron , chemistry , arylene , electronic structure , crystallography , conformational isomerism , steric effects , population , stereochemistry , computational chemistry , molecule , aryl , alkyl , demography , organic chemistry , sociology
The electronic structure and associated spectroscopic properties of ligand‐bridged, bimetallic ‘mixed‐valence’ complexes of the general form {M}(μ‐B){M + } are dictated by the electronic couplings, and hence orbital overlaps, between the metal centers mediated by the bridge. In the case of complexes such as [{Cp*(dppe)Ru}(μ‐C≡CC 6 H 4 C≡C){Ru(dppe)Cp*}] + , the low barrier to rotation of the half‐sandwich metal fragments and the arylene bridge around the acetylene moieties results in population of many energy minima across the conformational energy landscape. Since orbital overlap is also sensitive to the particular mutual orientations of the metal fragment(s) and arylene bridge through a Karplus‐like relationship, the different members of the population range exemplify electronic structures ranging from strongly localized (weakly coupled Robin‐Day Class II) to completely delocalized (Robin‐Day Class III). Here, we use electronic structure calculations with the hybrid density functional BLYP35‐D3 and a continuum solvent model in combination with UV‐vis‐NIR and IR spectroelectrochemical studies to show that the conformational population in complexes [{Cp*(dppe)Ru}(μ‐C≡CArC≡C){Ru(dppe)Cp*] + , and hence the dominant electronic structure, can be biased through the steric and electronic properties of the diethynylarylene (Ar) moiety (Ar=1,4‐C 6 H 4 , 1,4‐C 6 F 4 , 1,4‐C 6 H 2 ‐2,5‐Me 2 , 1,4‐C 6 H 2 ‐2,5‐(CF 3 ) 2 , 1,4‐C 6 H 2 ‐2,5‐ i Pr 2 ).