Département de chimie moléculaire

In search of robust catalysts for redox transformations such as the hydrogen evolution reaction (HER) or CO2 to CO reduction, we stepped on the previously reported meso-tetrakis(3,4,5-trimethoxyphenyl)porphyrinato cobalt(II) complex [Co(TTMPP)]. We prepared [Co(TTMPP)] in good yields and characterized it by IR, UV-vis absorption, photoluminescence spectroscopy, and cyclic voltammetry (CV). The [Co(TTMPP)] was used as a homogeneous catalyst for the electrochem. formation of H2 (HER) in DMF (N,N'-dimethylformamide)/TFA (trifluoroacetic acid) and DMF/EtN3BF4 solutions, with high faradic efficiencies (FE). Addnl., the reduction of CO2 to CO in DMF under a CO2 atm was catalyzed in DMF/TFE (TFE = 2,2,2-trifluoroethanol) and DMF/PhOH with high FE and only traces of H2 as a byproduct. Turnover frequencies of 15.80 or 9.33 s-1, resp. were determined from CV experiments or controlled potential electrolysis in the presence of 1eq. TFE. They were lower with PhOH as proton source with 13.85 or 8.31 s-1, resp. Further, [Co(TTMPP)] as a solid catalyst (suspension) allowed the photodecomposition of the organic dyes methylene blue (MB) and rhodamine B (RhB) using H2O2 under visible light irradiation The photocatalyst was photostable over five cycles. A photocatalytic mechanism was proposed based on trapping experiments of reactive oxygen species.