Photocatalytic hydrogen production from acidic aqueous solution in BODIPY-cobaloxime-ascorbic acid homogeneous system

Iodinated boron dipyrromethene (BODIPY) dyes with 8-hydroxyl-quinoline or phenylamine moiety at the meso-position on the BODIPY core were used as efficient photosensitizers (PSs) of three-component light-driven production of H₂ system from acidic aqueous solution in conjunction with a cobaloxime [Co^III(dmgH)₂PyCl] (dmgH = dimethylglyoximate, and py = pyridine) as proton-reducing catalyst and ascorbic acid (H₂A) as sacrificial electron donor. This is the first example of BODIPYs as homogeneous hydrogen-generating PSs employed in the acidic aqueous conditions. That they are active in the acidic solutions and inactive in the basic conditions may indicate that the extent of competition between intramolecular and intermolecular electron transfer reactions exists. Efficient bimolecular electron transfer reaction between PS and molecular catalyst is needed to make H₂ production, while the intramolecular electron transfer of PS may curb H₂ production. The results underscore that the chemical modification of BODIPYs can be performed, thus allowing for the transformation of acid and base conditions for the light-driven H₂ production.