Variable oxidation state sulfur-bridged bithiazole ligands tune the electronic properties of ruthenium(ii) and copper(i) complexes

The synthesis of homoleptic and heteroleptic ruthenium(ii) and copper(i) complexes containing sulfur-bridged bithiazole ligands of varying oxidation states are reported. The complexes have been characterized using 1D and 2D NMR spectroscopy, X-ray single crystal diffraction, electrochemistry, UV-vis absorbance and fluorescence spectroscopy. The stability, photophysical and electrochemical properties were found to be dependent on the oxidation state of the non-coordinating sulfur. The ruthenium and copper species were found to be non-emissive in solution at room temperature, though all displayed weak emission when doped in a PMMA matrix, which increased in intensity on cooling to 77 K. The electrochemical HOMO-LUMO gap was found to be dependent on the oxidation state of the sulfur in the bridging ligand in all complexes, illustrating an additional handle for tuning electrochemical properties.