Rhenium(I) and platinum(II) complexes with diimine ligands bearing acidic phenol substituents: hydrogen-bonding, acid-base chemistry and optical properties

Tricarbonylchloro-rhenium(I) (1-4) and catecholato-platinum(II) complexes (6, 7) of diimine ligands bearing phenol and O-protected phenol substituents have been prepared and fully characterised including single crystal structure analyses of 1, 4 and 7. The redox behaviour of the catecholato platinum(II) complexes 6 and 7 has been probed by cyclic voltammetry, preparative oxidation and EPR spectroscopy (6(center dot+), 7(center dot+)). Reversible deprotonation of the hydroxy substituted complexes 1, 3 and 6 to 1(-), 3(-) and 6(-) resulted in significant changes in their electronic spectra. The luminescence properties of the diamagnetic complexes have been investigated using emission spectroscopy. DFT and TD-DFT calculations were invoked to shed some light onto the geometric and electronic structures as well as the experimental spectroscopic properties of the neutral complexes 1-7, the radical cations 6(center dot+) and 7(center dot+) and the conjugate bases 1(-), 3(-) and 6(-).