Crystallographic Degrees of Freedom and Static/Dynamic Mixed-Valence States in One-Dimensional Rhodium–Dioxolene Complexes

We report a crystallographic and electronic-structure study on three rhodium–dioxolene complexes that illustrate how crystallographic degrees of freedom control static and dynamic mixed-valence states in one-dimensional（1D）assemblies. Complexes｛［Rh（3,6-DBDiox-4,5-S2CO）（CO）2］4・hexane｝∞（4） and ［Rh（3,6-DBDiox-4,5-S2CO）（CO）2］4（5）share essentially the same tetrameric Rh4 core but form, respectively, a 1D chain of tetramers stabilized by solvent inclusion and a discrete tetramer crystal. XPS and metrical oxidation state （MOS） analysis reveal Rh （I,II） mixed-valence states with an integer charge transfer of one electron per tetramer. In contrast, ［Rh（3,6-DBDiox-4-NO2）（CO）2］∞（6）forms an equidistant 1D Rh chain and exhibits a first-order phase transition accompanied by a small fractional electron transfer per Rh and a large-amplitude Rh–Rh vibration. DFT and TD-DFT calculations show strong dσ*（Rh）–π*（SQ） mixing, accounting for the broad NIR–mid-IR bands and 1D conduction. By comparing tetramer-based and chain-based systems, we establish a unified picture of static versus dynamic mixed-valence states in dimension-controlled rhodium–dioxolene assemblies.