Non-luminescent 1,2-diiminetricarbonylrhenium(I) chloride complexes - Synthesis, electrochemical and spectroscopic properties of Re(DIAN)(CO)(3)Cl with DIAN = p-substituted bis(arylimino)acenaphthene

Re(1,2-diimine)(CO)(3)Cl compounds containing the p-substituted bis(arylimi no)acenaphthene derivatives DIAN-R with R = H, Me, OMe, Br, and Cl were pre pared and characterized. The diimine ligands of this series provide unoccup ied orbitals at rather low energies and display a pronounced pi-accepting s trength. This feature determines the electrochemical and spectroscopic prop erties of the Re(DIAN-R)(CO)(3)Cl complexes. All compounds show rhenium(I) to pi* (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)(3)Cl comple xes are nonluminescent both in fluid solution at 298 K and in solvent glass at 77 K.