Probing the Transition between the Localised (Class II) and Localised‐to‐Delocalised (Class II–III) Regimes by Using Intervalence Charge‐Transfer Solvatochromism in a Series of Mixed‐Valence Dinuclear Ruthenium Complexes

Abstract

Intervalence charge-transfer (IVCT) solvatochromism studies on the diastereoisomeric forms of [{Ru(bpy)(2)}(2)(mu-BL)](5+) (bpy=2,2'-bipyridine; BL=a series of di-bidentate polypyridyl bridging ligands) reveal that the solvent dependencies of the IVCT transitions decrease as the "tail" of the bridging ligand is extended, and the extent of delocalisation increases. Utilising a classical theoretical approach for the analysis of the intervalence charge-transfer (IVCT) solvatochromism data, the subtle and systematic variation in the electronic properties of the bridging ligands can be correlated with the shift between the localised (class II) and localised-to-delocalised (class II-III) regimes. The investigation of the diastereoisomeric forms of two series of complexes incorporating analogous structurally rigid (fused) and nonrigid (unfused) bridging ligands demonstrates that the differences in the IVCT characteristics of the diastereoisomers of a given complex are accentuated in the latter case, due to a stereochemically induced redox asymmetry contribution. The marked dependence of the IVCT transitions on the stereochemical identity of the complexes provides a quantitative measure of the fundamental contributions of the reorganisational energy and redox asymmetry to the intramolecular electron-transfer barrier at the molecular level.

Direct Observation of Mixed‐Valence and Radical Cation Dimer States of Tetrathiafulvalene in Solution at Room Temperature: Association and Dissociation of Molecular Clip Dimers Under Oxidative Control

“…The addition of [ (2, These results suggest that both the chemical and electrochemical oxidations proceeded though the same four intermediary dimers. [19] As expected, when we added a large excess of [(2,4-Br 2 C 6 H 3 ) 3 N]A C H T U N G T R E N N U N G [SbCl 6 ] to the solution 1 in CH 3 CN, the absorption at 946 nm for the radical cation-radical cation dimer state disappeared and the resulting spectrum, which had absorptions at 440 and 598 nm, was similar to that obtained after the oxidation of monomeric TTF derivative 2 under the same conditions ( Figure 6). …”

Electronic Structures of Divinylchalcogenophene‐Bridged Biruthenium Complexes: Exploring Trends from O to Te

“…Accurate interpretation of the resulting heavily overlapped and poorly resolved optical absorption band envelopes is challenging. Increasingly, evidence from other spectroscopic methods with a range of timescales (e.g., IR, EPR, Mössbauer), , , supported by computational studies, is used to explore the electronic structures of the [L n M(µ‐bridge)ML n ] + complexes, many of which do not conform well to the traditional interpretations based on metal‐based redox processes in static molecular structures.…”

Synthesis and (Spectro)electrochemical Behavior of 2,5-Diferrocenyl-1-phenyl-1H-phosphole

“…Compounds with two redox-active transition metal fragments connected via a π-conjugated spacer unit are of considerable interest as they can be regarded as model compounds for molecular wires. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] In the last years huge efforts in the development of molecules in which the two redox-active metal centers exhibit a pronounced electronic communication across the spacer unit have been made. During the course of these investigations, a wide variety of π-conjugated spacers have been explored including systems based on all-carbon chains, vinylogous moieties, aromatic hydrocarbons, metallacycles or heteroatom-containing groups.…”