6533b85efe1ef96bd12c0861

RESEARCH PRODUCT

Understanding light-driven H 2 evolution through the electronic tuning of aminopyridine cobalt complexes

subject

description

A new family of cobalt complexes with the general formula [CoII(OTf)2(Y,XPyMetacn)] (1R,Y,XPyMetacn ¼ 1-[(4-X-3,5-Y-2-pyridyl)methyl]-4,7-dimethyl-1,4,7-triazacyclononane, (X ¼ CN (1CN), CO2Et (1CO2Et), Cl (1Cl), H(1H), NMe2 (1NMe2)) where (Y ¼ H, and X ¼ OMe when Y ¼ Me (1DMM)) is reported. We found that the electronic tuning of the Y,XPyMetacn ligand not only has an impact on the electronic and structural properties of the metal center, but also allows for a systematic water-reduction-catalytic control. In particular, the increase of the electron-withdrawing character of the pyridine moiety promotes a 20-fold enhancement of the catalytic outcome. By UV-Vis spectroscopy, luminescence quenching studies and Transient Absorption Spectroscopy (TAS), we have studied the direct reaction of the photogenerated [IrIII(ppy)2(bpyc )] (PSIr) species to form the elusive CoI intermediates. In particular, our attention is focused on the effect of the ligand architecture in this elemental step of the catalytic mechanism. Finally, kinetic isotopic experiments together with DFT calculations provide complementary information about the rate-determining step of the catalytic cycle We would like to thank the European Commission for the ERCCG-2014-648304 (J.Ll.-F) project. The financial support from ICIQ Foundation and CELLEX Foundation through the CELLEXICIQ high throughput experimentation platform and the Starting Career Program is gratefully acknowledged. We also thank CERCA Programme (Generalitat de Catalunya); The MINECO is acknowledged for a FPU fellowship to A.C (AP2012- 6436) and ICIQ-IPMP program (F.F.) and Severo Ochoa Excellence Accreditation 2014–2018 (SEV-2013-0319). J.M.L. is grateful for financial support from the Spanish MINECO CTQ2014-52525-P and the Catalan DIUE 2014SGR931. J.P-P. gratefully acknowledge CTQ2014-60174-P (partially co-financed with FEDER funds), Maria de Maeztu (MDM-2015-0538), RyC contract to MGB) and Fundación Ramón Areces for financial support