Hydrogen is considered as a potential solution to the energy crisis facing today because it is a renewable, clean, non-toxic energy source. Hydrogen production based on earth-abundant metals complexes has received great interest due to their stability in aqueous solutions, avoiding the use of organic solvents etc. Our previous work showed that significant improvement in homogeneous catalytic H2 evolution could be achieved by ligand modification of [Co(DPA-Bpy)(H2O)](PF6)3 (DPA-Bpy = N,N-bis(2-pyridinylmethyl)-2,2'-bipyridine-6-methanamine). To fully understand the electronic and steric effects of axial group that lies trans to the proposed cobalt hydride intermediate, two cobalt complexes [Co(DPA-1-MPI)(H2O)](PF6)3 (DPA-1-MPI = N,N-bis(2-pyridinylmethyl)[3-(2-pyridinyl)-isoquinoline]-1-methanamine), and [Co(DPA-3-MPI)(H2O)](PF6)3 (DPA-3-MPI = N,N-bis(2-pyridinylmethyl)[1-(2-pyridinyl)isoquinoline]-3-methanamine) with pyridyls replaced by isoquinoline groups in axial position were synthesized and their activity for electro- and photocatalytic hydrogen production in aqueous solution were investigated. Comparisons of structures and reactivity suggest that a conjugate and planar bipyridyl unit or its isoquinoline analog plays a key role for H2 evolution catalysis. Such a planar and conjugate structural feature could promote stability to the low valent CoI species. Furthermore, research on cobalt complexes with new ligand scaffolds for hydrogen production in aqueous solutions will be discussed.

Molecular cobalt complexes with pentadentate ligands for electro- and photocatalytic hydrogen generation in aqueous solution

2019 Fall National Meeting

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