Electronic π-Delocalization Boosts Catalytic Water Oxidation by Cu(II) Molecular Catalysts Heterogenized on Graphene Sheets

Journal of the American Chemical Society

5 years ago

Electronic π-Delocalization Boosts Catalytic Water Oxidation by Cu(II) Molecular Catalysts Heterogenized on Graphene Sheets

Pere Monge, Dooshaye Moonshiram, Antoni Llobet, Victor S. Batista, Pablo Garrido-Barros, Antonio Picón, Carolina Gimbert-Suriñach

A molecular water oxidation catalyst based on the copper complex of general formula [(L_py)Cu^II]^2–, 2^2–, (L_py is 4-pyrenyl-1,2-phenylenebis(oxamidate) ligand) has been rationally designed and prepared to support a more extended π-conjugation through its structure in contrast with its homologue, the [(L)Cu^II]^2– water oxidation catalyst, 1^2– (L is o-phenylenebis(oxamidate)). The catalytic performance of both catalysts has been comparatively studied in homogeneous phase and in heterogeneous phase by π-stacking anchorage to graphene-based electrodes. In the homogeneous system, the electronic perturbation provided by the pyrene functionality translates into a 150 mV lower overpotential for 2^2– with respect to 1^2– and an impressive increase in the k_cat from 6 to 128 s^–1. Upon anchorage, π-stacking interactions with the graphene sheets provide further π-delocalization that improves the catalytic performance of both catalysts. In this sense, 2^2– turned out to be the most active catalyst due to the double influence of both the pyrene and the graphene, displaying an overpotential of 538 mV, a k_cat of 540 s^–1 and producing more than 5300 TONs.

Publisher URL: http://dx.doi.org/10.1021/jacs.7b06828

DOI: 10.1021/jacs.7b06828