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

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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