Infrared Spectroelectrochemistry of Iron-Nitrosyl Triarylcorroles. Implications for Ligand Noninnocence

Abstract

Recent DFT calculations have suggested that iron nitrosyl triarylcorrole complexes have substantial {FeNO} 7 –corrole •2– character. With this formulation, reduction of Fe(C)(NO) complexes, where C = triarylcorrole, should be centered on the corrole macrocycle rather than on the {FeNO} 7 moiety. To verify this proposition, visible and infrared spectroelectrochemical studies of Fe(C)(NO) were carried out and the results were interpreted using DFT (B3LYP/STO-TZP) calculations. The first reduction of Fe(C)(NO) led to significant changes in the Soret and Q-band regions of the visible spectrum as well as to a significant downshift in the ν NO and changes in the corrole vibrational frequencies. DFT calculations, which showed that the electron was mostly added to the corrole ligand (85%), were also able to predict the observed shifts in the ν NO and corrole bands upon reduction. These results underscore the importance of monitoring both the corrole and nitrosyl vibrations in ascertaining the site of reduction. By contrast, the visible spectroelectrochemistry of the second reduction revealed only minor changes in the Soret band upon reduction, consistent with the reduction of the FeNO moiety.

Nature of the copper-nitrosyl intermediates of copper nitrite reductases during catalysis

“…Such a description parallels that for formal {FeNO} 6 corroles, which are now thought to be better described as {FeNO} 7 -corrolec 2À assemblies. 26,27 This insight also explains the surprisingly similar geometries of the CuNO units for the {CuNO} 10 and {CuNO} 11 states for the L2 supporting ligand.…”

“…The results proved stable across a wide range of exchange-correlation functionals. Note, however, that broken-symmetry solutions for M S ¼ 0 systems are oen only obtainable with hybrid functionals (such as B3LYP, PBE0, and M06-L), [18][19][20][21][22][23][24][25][26][27] which was also the case in this study. Fig.…”

Heavy-element–ligand covalence: ligand noninnocence in molybdenum and tungsten Viking-helmet Corroles

“…In recent years, metallocorroles have provided many examples of well-characterized noninnocent systems. [19][20][21][22] Key examples include MnCl, 23 FeCl, [9][10][11][12][13][14][15] FeNO, [24][25][26][27] Fe 2 (μ-O), 28 Copy 29 /DMSO 30 ( py = pyridine), Co-PPh 3 , 31 and Cu [32][33][34][35][36][37][38][39][40] corrole derivatives. It is worth noting that all these involve first-row transition metals.…”

Electronic Structure of Neutral and Anionic Iron–Nitrosyl Corrole. A Multiconfigurational and Density Matrix Renormalization Group Investigation

“…B3LYP calculations also uncovered considerable polyradical character within the {FeNO} 7 unit; thus, the ground-state electronic structure was described as consisting of an S = 3 / 2 Fe III with a d xy 2 d z 2 1 d xz 1 d yz 1 configuration coupled antiferromagnetically to an S = 1 NO – and an S = 1 / 2 corrole •2– . Very recently, an infrared spectroelectrochemical study provided evidence that the one-electron electroreduced product of FeNO triarylcorroles is best described as {FeNO} 7 –(corrole 3– ); in other words, the reduction occurs in a largely ligand-centered manner …”