title: Solid-state spectroscopic properties and the geometry of binuclear rhodium(I) diisocyanoalkane complexes.
abstract: A series of crystalline dinuclear rhodium complexes with different bridging diisocyano ligands and different counter ions have been studied by low-temperature crystallographic and solid-state spectroscopic techniques. The Rh-Rh distances vary from 4.5153(3) to 3.0988(7) angstroms, and the twist angles around the Rh-Rh line from 58.3(1) to 0 degree, both depending on the size and conformational rigidity of the bridging ligand. For very long distances as occur in the [Rh(2)(dimen)(4)](2+) salts the absorption is significantly blue-shifted compared to other complexes. For a given cation a shorter Rh-Rh bond gives a red shift of the phosphorescence emission band, indicating a smaller energy gap between the ground and emitting excited states. An exception occurs for the [Rh(2)(1,6-diisocyanohexane)(4)](2+) ion, in which dimer formation in the calixarate salt lengthens the Rh-Rh intramolecular bond length without affecting the emission spectrum.
authors.affiliation: Chemistry Department, University at Buffalo, State University of New York, Buffalo, NY 14260, USA.
authors.forename: Oksana
authors.initials: O
authors.lastname: Gerlits
authors.forename: Andrey Yu
authors.initials: AY
authors.lastname: Kovalevsky
authors.forename: Philip
authors.initials: P
authors.lastname: Coppens