Dioxygenation Reaction of a Cobalt-Nitrosyl: Putative Formation of a Cobalt–Peroxynitrite via a {Co^III(NO)(O₂^–)} Intermediate

Abstract

A cobalt-nitrosyl complex, [(BPI)Co(NO)(OAc)], 1 {BPI = 1,3-bis(2'-pyridylimino)isoindol} was prepared and characterized. Structural characterization revealed that the cobalt center has a distorted square pyramidal geometry with the NO group coordinated from the apical position in a bent fashion. The addition of dioxygen (O) to the dichloromethane solution of complex 1 resulted in the formation of nitro complex, [(BPI)Co(NO)(OAc)], 2. It was characterized structurally. Kinetic studies suggested the involvement of an associative mechanism. FT-IR spectroscopic studies suggested the formation of the intermediate 1a [(BPI)Co(NO)(O)(OAc)] in the reaction. The intermediate 1a decomposed to complex 2 via a presumed peroxynitrite intermediate which was implicated by its characteristic phenol ring nitration reaction.

Artificial Control of Cell Signaling Using a Photocleavable Cobalt(III)–Nitrosyl Complex

“…Thec obalt(III)-nitrosyl complex, [Co III (MDAP)(NO)-(CH 3 CN)] 2+ (1), was generated by bubbling NO through the CH 3 CN solution of [Co II (MDAP)(CH 3 CN) 2 ] 2+ under an N 2 atmosphere at À40 8 8C. [8][9][10][11][12][13][14] The Fourier transform infrared (FT-IR) spectrum of 1 displays an NO stretching band at 1634 cm À1 (Figure 1b,inset), which lies within the range of previously reported values for {CoNO} 8 complexes (1584-1716 cm À1 ). As shown in Figure 1b, the UV/Vis spectrum of 1 in CH 3 CN contains characteristic absorption bands at l max = 330 (e = 4.3 10 3 m À1 cm À1 )a nd 480 nm (e = 4.1 10 2 m À1 cm À1 ), which are similar to those of previously reported cobalt(III)-nitrosyl complexes.…”

“…Thec olor of the reaction mixture changed from orange-red to dark red. [8][9][10][11][12][13][14][15] The 1 HNMR signals of 1 are observed in the 0-10 ppm region, indicating al ow-spin diamagnetic ground state (Supporting Information, Figure S2). [8][9][10][11][12][13][14] The Fourier transform infrared (FT-IR) spectrum of 1 displays an NO stretching band at 1634 cm À1 (Figure 1b,inset), which lies within the range of previously reported values for {CoNO} 8 complexes (1584-1716 cm À1 ).…”

“…As shown in Figure 1b, the UV/Vis spectrum of 1 in CH 3 CN contains characteristic absorption bands at l max = 330 (e = 4.3 10 3 m À1 cm À1 )a nd 480 nm (e = 4.1 10 2 m À1 cm À1 ), which are similar to those of previously reported cobalt(III)-nitrosyl complexes. [8][9][10][11][12][13][14][15][16] Single crystals of 1 were grown from CH 3 CN/Et 2 Oa t À40 8 8C. [8][9][10][11][12][13][14][15] The 1 HNMR signals of 1 are observed in the 0-10 ppm region, indicating al ow-spin diamagnetic ground state (Supporting Information, Figure S2).…”

“…These results point to a{ CoNO} 8 description for 1. [8][9][10][11][12][13][14][15][16] Single crystals of 1 were grown from CH 3 CN/Et 2 Oa t À40 8 8C. TheX -ray crystal structure of 1 exhibits am ononuclear end-on cobalt-NO complex in ad istorted octahedral geometry,w ith four nitrogen (N) atoms of the macrocyclic MDAP ligand, one Nf rom CH 3 CN,a nd one Nf rom NO,a s shown in Figure 1c.The N1-O1 and Co1-N1 bond lengths in 1 are 1.097 (6) Table S2).…”

Direct Resonance Raman Characterization of a Peroxynitrito Copper Complex Generated from O2 and NO and Mechanistic Insights into Metal‐Mediated Peroxynitrite Decomposition

“…[27,28] Metal-coordinated peroxynitrites are of interest because of the intimate role that metals play in the regulation and processing of both NOC and O 2 C À , [3,[29][30][31][32] which may implicate metals as important factors in the physiological formation and transformation of peroxynitrite (Scheme 1). [33][34][35][36][37][38][39][40][41][42] Examples of stable peroxynitrite complexes are scarce, [43,44] and those containing vibrational (i.e., IR spectroscopic) information about the peroxynitrite ligand even more so. [33][34][35][36][37][38][39][40][41][42] Examples of stable peroxynitrite complexes are scarce, [43,44] and those containing vibrational (i.e., IR spectroscopic) information about the peroxynitrite ligand even more so.…”