Table 3. Screening bis-NHC Ir(iii) complexes for photo-catalysis ^a .

Entry b	PC	Conversion c /%	Yield c /%
1	1b	93	59
2	2b	1	0
3	4Meb	90	59
4	5b	90	52
5	6Hb	93	59
6	6Fb	80	44
7	7b	49	24
8	8b	11	7.3
9	9b	0.1	0

^aComplex 3a was not tested because of the low quantum yield (0.2%, see Table 1).

^bProcedure: substrate 50 μmol, PC (1 mol%), DIPEA (5 equiv.), HCOOH (2.5 equiv.) in 4 mL MeCN solution was degassed by nitrogen, and irradiated by blue light (12 W, λ_max = 462 nm) at ambient temperature for 4 h.

^cDetermined by ¹H NMR spectroscopy by adding internal standard of 5,5′-dimethyl-2,2′-bipyridine.