Pyranopterin Related Dithiolene Molybdenum Complexes as Homogeneous Catalysts for CO2 Photoreduction

Abstract

Summary

A photochemical reduction of CO₂ to formic acid or CO was shown using the novel dithiolene molybdenum complexes [K]2[MoO(Hqpdt)2] and [MoO(2Hqpdt)2][NBu4] in comparison to the previously reported complex [MoO(qpdt)2][NBu4]2 as catalysts in combination with photosensitizer Ru(bpy)3Cl2. Turnover numbers (TONs) of up to 83 for formic acid and 40 for CO were reached in acetonitrile for complex [MoO(2Hqpdt)2][NBu4]. The experiments were conducted under visible-light irradiation (λ = 400 nm) using BIH and TEOA as sacrificial electron donor (see section SEDs below).

Advances and special progress

Bioinspired dithiolene Mo-complexes as analogues of the active site of the FDH (formate dehydrogenase) were shown to be active as CO₂ photoreduction catalysts with formation of formic acid as the main product.

Content of the published article in detail

The article contains results for the reduction of CO₂ to CO or formic acid under visible-light catalysis using molybdenum complexes and a ruthenium-based photosensitizer. The catalytic system performs best (referring to the TON of formic acid production) in acetonitrile with complex [MoO(2Hqpdt)2][NBu4].

Catalyst

[K]2[MoO(Hqpdt)2] [MoO(2Hqpdt)2][NBu4] [MoO(qpdt)2][NBu4]2

Photosensitizer

Ru(bpy)3Cl2

Investigation

	cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	solvent A	.	.	.	λexc [nm]	.	TON CO	TON H2	TON HCOOH	.
1.	[MoO(qpdt)2][NBu4]2	0.05	Ru(bpy)3Cl2	0.5	BIH	0.1	MeCN				400		73	670	80
2.	[K]2[MoO(Hqpdt)2]	0.05	Ru(bpy)3Cl2	0.5	BIH	0.1	MeCN				400		13	51	31
3.	[MoO(2Hqpdt)2][NBu4]	0.05	Ru(bpy)3Cl2	0.5	BIH	0.1	MeCN				400		40	89	83

Investigation-Name: Table 1Export

Sacrificial Electron Donor

In this study, the experiments were done with the sacrificial electron donors TEOA (TEOA) and BIH (BIH).

Additives

In this study, no additives were tested.