Exploring the Full Potential of Photocatalytic Carbon Dioxide Reduction Using a Dinuclear Re₂Cl₂ Complex Assisted by Various Photosensitizers

Abstract

Abstract Photosensitizing units have already been applied to enable light‐driven catalytic reduction of CO 2 with mononuclear rhenium complexes. However, dinuclear catalytic systems that are able to activate CO 2 in a cooperative bimetallic fashion have only rarely been combined with photosensitizers. We here present detailed studies on the influence of additional photosensitizers on the catalytic performance of a dirhenium complex ( Re 2 Cl 2 ) and present correlations with spectroscopic measurements, which shed light on the reaction mechanism. The use of [Ir(dFppy) 3 ] ( Ir , dFppy=2‐(4,6‐difluorophenyl)pyridine)) resulted in considerably faster CO 2 to CO transformation than [Cu(xant)(bcp)]PF 6 ( Cu , xant=xantphos, bcp=bathocuproine). Emission quenching studies, transient absorption as well as IR spectroscopy provide information about the electron transfer paths of the intermolecular systems. It turned out that formation of double reduced species [Re 2 Cl 2 ] 2 − along with an intermediate with a Re−Re bond ( [ReRe] ) can be taken as an indication of multi‐electron storage capacity. Furthermore, under catalytic conditions a CO 2 ‐bridged intermediate was identified.