Sensitized Photocatalytic CO2 Reduction With Earth Abundant 3d Metal Complexes Possessing Dipicolyl-Triazacyclononane Derivatives

Abstract

Complexes based on nitrogen and sulfur containing ligands involving 3d metal centers are known for the electrocatalytic reduction of CO2. However, photocatalytical activation has rarely been investigated. We herein present results on the light-driven CO2 reduction using either Ir(dFppy)3 [Ir, dFppy = 2-(4,6-difluorophenyl)pyridine] or [Cu(xant)(bcp)]+, (Cu, xant = xantphos, bcp = bathocuproine) as photosensitizer in combination with TEA (triethylamine) as sacrificial electron donor. The 3d metal catalysts have either dptacn (dipicolyl-triazacyclononane, LN3) or dpdatcn (dipicolyl-diazathiocyclononane, LN2S) as ligand framework and Fe3+, Co3+ or Ni2+ as central metal ion. It turned out that the choice of ligand, metal center and solvent composition influences the selectivity for product formation, which means that the gaseous reduction products can be solely CO or H2 or a mixture of both. The ratio between these two products can be controlled by the right choice of reaction conditions. With using Cu as photosensitizer, we could introduce an intermolecular system that is based solely on 3d metal compounds being able to reduce CO2.

A CuICoII cryptate for the visible light-driven reduction of CO2

“…34 Interestingly, the second metal seemingly does not promote the catalysis at all, since the observed rates are in the similar range as for monometallic Co II -{N S N N } m (0.99 min −1 ). The decreased catalytic rates and formation of a precipitate during irradiation together with a few reports on +II metal complexes revealing decreased activity for CO 2 -to-CO conversion or tendency to demetallation upon directs N/S exchange in the ligand under reductive conditions, [41][42][43] let us to the conclusion that the lowered activity is due to decomposition of the {N S } site and consequently emphasises the importance of matching donor-acceptor properties of ligand and metal.…”

Enhanced Reactivity through Equatorial Sulfur Coordination in Nonheme Iron(IV)–Oxo Complexes: Insights from Experiment and Theory

“…Iodosylbenzene (PhIO) was prepared by a previously reported literature method . The ligands (L 1 and L 2 ) were synthesized with slight modifications from the reported procedure. − The iron­(II) complexes [Fe II (L 1 )­(CH 3 CN)]­(OTf) 2 ( 1a ) and [Fe II (L 2 )­(CH 3 CN)]­(OTf) 2 ( 2a ) were synthesized using dry acetonitrile as a solvent inside a Jacomex glovebox filled with argon. The iron­(IV)-oxo intermediates [Fe IV (L 1 )­(O)] 2+ ( 1b ) and [Fe IV (L 2 )­(O)] 2+ ( 2b ) were synthesized in acetonitrile under ambient conditions.…”

Homogeneous Systems Containing Earth‐Abundant Metal Complexes for Photoactivated CO2 Reduction: Recent Advances

“…In the latest work of the group of Schwalbe, a cobalt complex was prepared with the macrocyclic ligand 1,4‐di(picolyl)‐1,4,7‐triazacyclononane, ( Co1 , Figure 6). [36] The same ligand was used also for the coordination with Fe(II) and Ni(II), and the photoactivated CO 2 ‐reduction was mainly tested in combination with an iridium photosensitizer ( vide infra ). As Co1 gave the highest efficiency in that system, it was tested also in combination with the photosensitizer Cu1 (Table 2, entry 22).…”