Infrared and resonance Raman studies of metal cation sensors in which an azacrown ether is linked to (bpy)Re(CO)3via an alkenyl or alkynyl spacer

Abstract

Infrared and resonance Raman spectra of two [(bpy)Re(CO)₃L]⁺ complexes (bpy = 2,2′-bipyridine) in which the L ligand contains an aza-15-crown-5 ether that is attached to Re via an alkenyl- or alkynyl-pyridine spacer are reported. Vibrational assignments have been made by comparison with the spectra of model complexes and ligands, and with the results of density functional theory (DFT) calculations; they provide information on the structure and bonding within the L ligands in the complexes. The addition of alkali or alkaline-earth metal perchlorate salts to solutions of the complexes in acetonitrile results in mode-specific changes in the vibrational spectra: the magnitudes of the changes depend on the identity of the metal cation, and they are rationalised in terms of changes in structure and bonding caused by the metal cation binding to the azacrown.