Further studies of the photoinduced reduction of carbon dioxide mediated by tricarbonylbromo(2,2'-bipyridine)rhenium(I)

Abstract

Reported are mechanistic studies of the photoinduced reduction of carbon dioxide to carbon monoxide mediated by ReBr(CO),(bpy) (bpy is 2,2'-bipyridine). Water, ethanol, and perchlorate ion enhance the intensity of luminescence from the Re-to-bpy charge-transfer excited state, whereas bromide ion and triethylamine (TEA) quench this emission. In the case of the amine, the quenching process leads to prompt formation of [ReBr(CO),(bpy)]-. Additional, slower production of this 19e species by reduction of the parent complex by a TEA-derived radical is unimportant. Water and ethanol lower the quantum efficiency of CO formation, whereas Br-has little effect. Reduction of bicarbonate ion to CO can be excluded as an important pathway in the system. Patirradiation spectral changes occur over several hours, but the chemistry responsible for this behavior is unrelated to CO formation.

Ligand Variations in [ReX(diimine)(CO)3] Complexes: Effects on Photocatalytic CO2 Reduction

“…From the initial experiments on, the mechanism of this unprecedented reaction has been of great interest. [8,10,20,21] Many experiments have been carried out with the original catalysts 1 or 2, but studies of the catalytic performance with variations in the anion X -or the diimine ligand N ʝ N are rare. [13,20] We present in this study the synthesis and characterisation of two series of [ReX(diimine)(CO) 3 ] complexes and an investigation of the respective ligand effects on the photocatalytic activities.…”

Conversion of CO2 via Visible Light Promoted Homogeneous Redox Catalysis

“…Abstraction of a proton at this TEOA radical by a further TEOA molecule yields the carbon-centered radicals (Scheme 4) [12,[99][100][101][102]. Unlike the aminyl radical TEOA·, these carbon-centered radicals are strong reducing agents that prevent back electron transfer from the OER and are capable of donating a second electron [12,[99][100][101][102][103][104]. [107].…”

Umwandlung von Kohlendioxid mit Übergangsmetall‐Homogenkatalysatoren: eine molekulare Lösung für ein globales Problem?

“…Auch hier ist wieder die Bildung des einfach negativ geladenen Photosensibilisators durch Abfangen seines angeregten Zustandes mithilfe des Opferdonors der erste Schritt. [261] Dies führt zu einer instabilen 19-Valenzelektronenspezies, in der durch Dissoziation eines Liganden eine Koordinationsstelle frei wird. [260] Die Frage, welcher Ligand hierbei dissoziiert, wird in großer Breite in der Literatur diskutiert und ist in seinen mechanistischen Aspekten in einem kürzlich erschienenen Aufsatz zusammengefasst.…”