Synthesis, Characterization, Photophysical, and Computational Studies of Rhenium(I) Tricarbonyl Complexes Containing the Derivatives of Bipyrazine

The chloro and pyridinate derivatives of rhenium(I) tricarbonyl complexes containing the diimine ligands 2,2‘-bipyrazine (bpz) and 5,5‘-dimethyl-2,2‘-bipyrazine (Me2bpz) are reported. Absorption maxima occur in the visible
and ultraviolet regions of the spectrum; emission is structureless at room temperature and at 77 K; the infrared
spectrum consists of three carbonyl stretches; electrochemically, a reversible reduction, an irreversible reduction,
and an irreversible oxidation take place. Some ring protons are shielded and others deshielded in the presence of
the methyl substituents attached to the bpz ring. DFT and TDDFT calculations provide insight into interpreting
electronic and vibrational properties of the complexes. When compared to similar rhenium(I) tricarbonyl complexes
of 2,2‘-bipyridine (bpy) and 2,2‘-bipyrimidine (bpm), the Me2bpz complexes are comparable to bpm derivatives and
their properties are intermediate between those of bpy and bpz complexes.