Rhenium(I) trinuclear rings as highly efficient redox photosensitizers for photocatalytic CO2 reduction

Abstract

Summary

A photochemical reduction of CO₂ to CO or formic acid was shown using the bipyridine-based rhenium, ruthenium and manganese catalysts [Re(bpy)(CO)3(MeCN)][PF6] (100781), Ru(dtBubpy)(CO)2Cl2 (100573) or [Mn(dtBubpy)(CO)3(MeCN)][PF6] (100875) in combination with cyclic rhenium-based trinuclear redox photosensitizers. Turnover numbers (TONs) of up to 290 for formic acid were reached in DMA with the ruthenium complex Ru(dtBubpy)(CO)2Cl2 (100573) and photosensitizer (100877). For CO production, TONs of up to 98 were obtained in DMF with the rhenium complex [Re(bpy)(CO)3(MeCN)][PF6] (100781) and photosensitizer (100878). The experiments were conducted under visible-light irradiation (λ = 436 nm) using TEOA as sacrificial electron donor (see section SEDs below).

Advances and special progress

Re(I)-based trinuclear photosensitizers were developed and allowed for high product selectivities for CO or formic acid in CO₂ reduction attempts with different bipyridine-based catalysts.

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 bipyridine-based complexes and rhenium-based trinuclear rings as photosensitizers. The catalytic system performs best in DMA for formic acid production (referring to the TON of formic acid production) and in DMF for CO production.

Catalyst

[Re(bpy)(CO)3(MeCN)][PF6] (100781) Ru(dtBubpy)(CO)2Cl2 (100573) [Mn(dtBubpy)(CO)3(MeCN)][PF6] (100875)

Photosensitizer

(100730) [Show R-Groups]

Investigation

		cat	cat conc [µM]	PS	PS conc [mM]	solvent A	.	.	λexc [nm]	.	TON CO	.	.	.	.
(edit)	1.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100878	0.05	DMF			436		27
(edit)	2.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100878	0.05	DMF			436		98
(edit)	3.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100877	0.05	DMF			436		22
(edit)	4.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100877	0.05	DMF			436		71
(edit)	5.			Molecule:100877	0.05	DMF			436		6
(edit)	6.			Molecule:100877	0.05	DMF			436		8
(edit)	7.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100879	0.05	DMF			436		20
(edit)	8.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100879	0.05	DMF			436		32
(edit)	9.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100880	0.05	DMF			436		11
(edit)	10.	[Re(bpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100880	0.05	DMF			436		48

Investigation-Name: Table 1

		cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	solvent A	.	.	λexc [nm]	.	TON CO	TON H2	TON HCOOH	.	.	.	.
(edit)	1.	Ru(dtBubpy)(CO)2Cl2	0.05	Molecule:100877	0.05			DMF			436		20	72	290
(edit)	2.	Ru(dtBubpy)(CO)2Cl2	0.05	Molecule:100877	0.05	BI(OH)H	0.03	DMF			436		16	49	280
(edit)	3.	[Mn(dtBubpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100877	0.05			DMF			436		32		85
(edit)	4.	[Mn(dtBubpy)(CO)3(MeCN)][PF6]	0.05	Molecule:100877	0.05	BI(OH)H	0.03	DMF			436		80		60

Investigation-Name: Table 2

Sacrificial Electron Donor

In this study, the experiments were done with the sacrificial electron donor TEOA (100507).

Additives

In this study, no additives were tested.