Table 2.

Correlation of calculated and experimental mode frequencies for [Fe(Porph)(RIm)(XO)] (X = O, C or N) complexes. (All values in cm⁻¹.)

Complex	Method				Mode frequencies
		Fe–XO[a]			Fe–Im[b]			doming[c]		220–360 cm−1[d]
[Fe(TpivPP)(1-EtIm)(O2)]	NRVS[e]	571	417	393	196	174	134	118	78	296[f], 268, 282, 320, 330[g]
	DFT[h]	642	435	405	195	169	143	104	74/71	295[f], 268, 284, 302(2), 317, 329(2)
	rR[i]	~568	425[j]		Not observed			Not observed
[Fe(TpivPP)(2-MeHIm)(O2)]	NRVS[e]	563	419	389	187	175	130	119	80	300[f], 270, 278, 314, 325
[Fe(TpivPP)(1-MeIm)(O2)]	NRVS[k]	571	417	393	205	175	136	118	84	268, 286, 318, 327
[Fe(TPP)(1-MeIm)(CO)][l]	NRVS[e]	586	561	507	225	172		127	64	331[f], 241, 251, 320, 338
[Fe(TPP)(1-MeIm)(NO)][m]	NRVS[e]	565	473	440	149	175
tri-[Fe(TpFPP)(1-MeIm)(NO)][n]	NRVS	559	467	432	140	167
mono-[Fe(TpFPP)(1-MeIm)(NO)][n]	NRVS	560	474	433	153	177

^[a]These bands incorporate Fe–XO motions associated with bending and stretching modes.

^[b]The frequency with the motions that most closely resemble that of the classical Fe–Im stretch are bolded.

^[c]The frequency with the motion that most closely resembles that of the classical Fe doming mode is bolded.

^[d]Except as noted, these modes are in-plane.

^[e]Powder, in-plane, and out-of-plane measurements.

^[f]Out-of-plane.

^[g]Iron has in-plane and out-of-plane character.

^[h]Basis set for iron: TZVP; Closed-shell singlet.

^[i]Ref. 4, 5, 38.

^[j]Observed in some proteins only.

^[k]Powder data only.

^[l]Ref. 27.

^[m]Ref. 39.

^[n]Ref. 20.