Synthesis, characterization and crystal structure of rhenium(I) tricarbonyl diimine complexes coupled with their efficiency in producing hydrogen in a photocatalytic system

Herein, we present the synthesis and characterization of two complexes, namely [ReBr(CO)3amphen] (1) (amphen = 1,10-phenanthroline-5-amine) and [ReBr(CO)3pq] (2) (pq = 2-(2′pyridyl)quinoxaline); complex 2 is reported for the first time. The X-ray crystal structure of 2 has been determined. Electrochemical and photophysical studies have been performed to study the effect of the variation of the diimine ligand on the redox and optical properties of this class of compounds. Both complexes were used as photosensitizers for hydrogen production in a homogeneous photocatalytic system also carrying [Co(dmgH)2] as a hydrogen reaction catalyst, triethanolamine as an irreversible reductive quencher and AcOH as proton source. Complex 1 produces H2 after only 2 h irradiation while complex 2 requires 24 h indicating that the differences in the electronic properties influence their photosensitizing ability.