A Novel 2,6-Bis(8’-quinolinyl)pyridine Rhenium Compound

Abstract

Rhenium(I) polypyridine carbonyl complexes have been well-investigated because of their intense emission properties, capability as building blocks for multinuclear complexes, and catalytic activities. The reaction of 2,6-bis(8'-quinolinyl)pyridine (bqp) and rhenium pentacarbonyl chloride directly produces the tridentate complex fac,fac-[Re(bqp-κ 3 N)(CO) 3 ] (Cl). Coordination of the bqp occurs with nucleophilic displacement of the chloride by the free quinolinyl group to produce a pseudo-octahedral complex with mutually facial bqp-κ 3 N and carbonyl ligands. UV-vis absorptions are increased in the region between 300-450 nm and can be understood as a mix of MLCT and π-π* ligand centered transitions. Cyclic voltammetry shows the first oxidation is purely metal-based, Re(II/I), and is followed by the rapid loss of a carbon monoxide ligand. Similarly, reduction potentials are irreversible and are assigned as ligand-based bqp(π*) reductions. DFT and TD-DFT calculations support both optical and electrochemical assignments. The complex is emissive in solution at room temperature. Variable temperature experiments show that emission is consistent with MLCT (Case A) type emission.