Synthesis and photocatalytic principle of five azepine-type [FeFe] models photocatalysts based on isophthalonitrile

Five azepine-type [FeFe] models (1–5) containing aniline structures were synthesized by classical amine condensation reaction. These models were characterised by 1H and 13C NMR, FTIR, and elemental analyses. Subsequently, the photocatalytic performance of the catalysts for hydrogen production was studied. The photocatalytic system consists of photosensitizer (2,4,5,6-Tetrakis(diphenylamino)isophthalonitrile), catalysts (1–5), solvent (DMF/H2O) and electron donor (NEt3). Under the optimized conditions, the maximum hydrogen production of the catalytic system (1, 0.34 mg) could reach 0.908 mmol (20 mL) within 1 h. The catalysts still had certain catalytic activity after 20 h of photocatalytic reaction. During a catalytic time of up to 20 h, catalyst 1 had the highest number of catalytic cycles. Moreover, the effect of catalyst concentration on hydrogen production was studied, and a possible catalytic mechanism was proposed.