Non-Luminescent 1,2-Diiminetricarbonylrhenium(I) Chloride Complexes – Synthesis, Electrochemical and Spectroscopic Properties of Re(DIAN)(CO)3Cl with DIAN = p-Substituted Bis(arylimino)acenaphthene

Abstract

Re(1,2-diimine)(CO)3Cl compounds containing the p-substituted bis(arylimino)acenaphthene derivatives DIAN-R with R = H, Me, OMe, Br, and Cl were prepared and characterized. The diimine ligands of this series provide unoccupied orbitals at rather low energies and display a pronounced π-accepting strength. This feature determines the electrochemical and spectroscopic properties of the Re(DIAN-R)(CO)3Cl complexes. All compounds show rhenium(I) to π*(diimine) metal-to-ligand charge transfer (MLCT) absorptions in the visible spectral region. The maxima of these CT bands systematically shift upon modification of the substituents R and are sensitive to variations of the solvent polarity (negative solvatochromism). Re(DIAN-R)(CO)3Cl complexes are non-luminescent both in fluid solution at 298K and in solvent glass at 77K.