Synthesis, crystal structure and photochemical H2 generation of a Co-based supramolecular assembly containing a bisthienyl Bodipy sensitizer

Abstract

In this contribution, a bisthienyl-substituted Bodipy sensitizer (B1) was synthesized and further axially anchored to one cobalt catalytic center via a pyridyl group located in the 8-position of the B1, affording a new sensitizer-catalyst supramolecular assembly (Co-B1). The supramolecular structure of Co-B1 was determined through single-crystal X-ray diffraction analysis, and showed nearly orthogonal stereochemistry between sensitizer B1 and Co catalyst. Visible light-driven H2-evolution performance of Co-B1 was investigated in aqueous solution with triethylamine (Et3N) as an electron donor, which displayed efficient H2 evolution activity and stability. DFT calculations indicated transition of HOMO → LUMO from the π-conjugated Bodipy B1 anion to the Co fragment is an intramolecular electron-transfer process. Notably, the present artificial photosynthetic system is an example of an absolutely noble-metal free supramolecular system for photochemical H2 generation from water using non-halogenated dye-catalyst assembly.