Iron(II) bis(pyrazolyl)phenanthroline complexes as robust and efficient homogeneous catalysts for CO2-to-CO conversion under visible light

Imported from: /opt/uploadtmp/1-s2.0-S0021951726000072-main_6a35513256656.pdf

This paper reports a family of homogeneous Fe(II) bis(pyrazolyl)phenanthroline complexes, [Fe(bpzRphen)(H2O)2]X2 (Fe1–Fe4), for visible-light-driven CO2 reduction in MeCN/H2O using [Ru(bpy)3]2+ as photosensitizer and BIH as sacrificial donor. Under blue-light irradiation (462 nm), all complexes produced CO as the major product with minor H2 and no significant formate or CH4. At 50 μM catalyst, Fe2 gave the highest activity (TONCO 1318, 84% CO selectivity), while Fe4 gave the highest selectivity (TONCO 1265, 91% CO selectivity). Optimization with Fe2 showed strong dependence on catalyst loading, irradiation time, water content, and BIH concentration. The best reported performance was obtained at low catalyst loading, where Fe2 reached TONCO 23,138 after 24 h and TONCO 9754 after 4 h with TOFCO 2438 h−1. A CO quantum yield of 7.6% at 462 nm was explicitly reported for Fe2 under low loading.

		cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	.	.	solvent A	.	.	.	.	.	.	λexc [nm]	.	TON CO	.	.	TON H2	.	.	.	.
(edit)	1.	[[[Fe(bpzphen)(H2O)2](BF4)2 (Fe1) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		987			187
(edit)	2.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1318			243
(edit)	3.	[[[Fe(bpzPhphen)(H2O)2](ClO4)2 (Fe3) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		847			205
(edit)	4.	[[[Fe(bpzCF3phen)(H2O)2](ClO4)2 (Fe4) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1265			133
(edit)	5.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		311			51
(edit)	6.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1578			296
(edit)	7.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1593			300
(edit)	8.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		2			22
(edit)	9.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1352			285
(edit)	10.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		661			191
(edit)	11.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		621			77
(edit)	12.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	25.0 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		2086			123
(edit)	13.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	12.5 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		4259			276
(edit)	14.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	6.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		10			423.7 h-1
(edit)	15.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	3.12 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		23			964.1 h-1
(edit)	16.	[[[Fe(bpzphen)(H2O)2](BF4)2 (Fe1) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	17.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		9754
(edit)	18.	[[[Fe(bpzPhphen)(H2O)2](ClO4)2 (Fe3) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	19.	[[[Fe(bpzCF3phen)(H2O)2](ClO4)2 (Fe4) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	20.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	27.5 mM			MeCN							462 nm (blue LED strip)		221

Investigation-Name: inv0

Imported from: /opt/uploadtmp/1-s2.0-S0021951726000072-main_6a355df670af9.pdf

This paper reports a family of homogeneous iron(II) bis(pyrazolyl)phenanthroline complexes, [Fe(bpzRphen)(H2O)2]X2 (Fe1–Fe4), for visible-light-driven CO2 reduction to CO using [Ru(bpy)3]2+ as photosensitizer and BIH as sacrificial electron donor in MeCN/H2O. All four complexes are active and selective for CO formation under 462 nm LED irradiation. Under the standard conditions (50 μM catalyst, 0.3 mM [Ru(bpy)3]2+, 0.11 M BIH, CO2-saturated MeCN/H2O, 308 K, 24 h), Fe2 gave the highest activity (TONCO = 1318, 84% CO selectivity), while Fe4 gave the highest selectivity in the series (TONCO = 1265, 91% CO selectivity). At lower Fe2 loading (3.12 μM), the system reached TONCO = 23,138 after 24 h and TONCO = 9754 after 4 h, with a total quantum yield of 8.24% reported in the abstract and 7.6% at 462 nm in the main text.

		cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	.	.	solvent A	.	.	.	.	.	.	λexc [nm]	.	TON CO	.	.	TON H2	.	.	.	.
(edit)	1.	[[[Fe(bpzphen)(H2O)2](BF4)2 (Fe1) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		987			187
(edit)	2.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1318			243
(edit)	3.	[[[Fe(bpzPhphen)(H2O)2](ClO4)2 (Fe3) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		847			205
(edit)	4.	[[[Fe(bpzCF3phen)(H2O)2](ClO4)2 (Fe4) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1265			133
(edit)	5.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		311			51
(edit)	6.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1578			296
(edit)	7.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1593			300
(edit)	8.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		2			22
(edit)	9.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		1352			285
(edit)	10.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		661			191
(edit)	11.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		621			77
(edit)	12.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	25.0 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		2086			123
(edit)	13.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	12.5 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		4259			276
(edit)	14.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	6.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		10			423.7 h-1
(edit)	15.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	3.12 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		23			964.1 h-1
(edit)	16.	[[[Fe(bpzphen)(H2O)2](BF4)2 (Fe1) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	17.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)		9754
(edit)	18.	[[[Fe(bpzPhphen)(H2O)2](ClO4)2 (Fe3) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	19.	[[[Fe(bpzCF3phen)(H2O)2](ClO4)2 (Fe4) ]]	3.25 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	0.11 M			MeCN							462 nm (blue LED strip)
(edit)	20.	[[[Fe(bpzMe2phen)(H2O)2](BF4)2 (Fe2) ]]	50 μM	[[[Ru(bpy)3]2+ ]]	0.3 mM	BIH	27.5 mM			MeCN							462 nm (blue LED strip)		221

Investigation-Name: inv0