Table 1. Vibrational frequencies (cm^–1) observed for complex 1 and 2, and those reported for the H-cluster in the H_ox, H_ox-CO and H_red′ state with the native [2Fe]^adt-cofactor and the semi-synthetic [2Fe]^pdt-cofactor.

Species	CN–	Terminal CO	Bridging CO	Ref.
1	2056	1980, 1944, 1910	—	This work and ref. 3
2	2078, 2036	(2005), 1984, 1953 (1856)	1792	This work
Hox a , b	2088, 2072	1964, 1940	1800	21
Hox-pdt a , c	2090, 2072	1966, 1941	1810	22
Hox-CO a , b	2092, 2084	2013, 1970, 1964	1810	21
Hred′ a , b	2083, 2067	1962, 1933	1791	23
Hred′-pdt a , c	2084, 2065	1963, 1933	1798	22

^aObserved for HydA1 from Chlamydomonas reinhardtii.

^bNative H-cluster.

^cSemi-synthetic H-cluster incorporating the [2Fe]^pdt (= [Fe₂(pdt)(CO)₃(CN₂)]^2–) cofactor.