Microvoltammetry and in situ FTIR, ESR, and UV-visible spectroelectrochemical studies of nitrosyl(tetrophenylporphyrinato)cobalt oxidation/reduction in dichloromethane

Conversion of Nitric Oxide into Nitrous Oxide as Triggered by the Polarization of Coordinated NO by Hydrogen Bonding

“…Only a few non‐porphyrin‐supported {Co(NO)} 9 cobalt–nitrosyl complexes have been described, and no thorough characterization of a reduced {Co(NO)} 9 or {Co(NO)} 8 radical‐anion cobalt–nitrosyl porphyrinoid has been reported, possibly as a result of the facile denitrosylation of such compounds upon reduction. Furthermore, an electron‐rich metal–nitrosyl porphyrin in a reduced state usually requires an electron‐deficient porphyrinato ligand for stabilization. For example, {Fe(NO)} 8 [Co(Cp) 2 ][Fe(TFPPBr 8 )(NO)] was structurally characterized by the use of an extremely electron‐deficient porphyrin, TFPPBr 8 2− , as the supporting ligand .…”

“… Upon the electrolysis of 1 in CH 2 Cl 2 under −1.2 V (vs. a pseudoreference silver‐wire electrode), the IR SEC spectrum showed a ν NO shift from 1616 to 1521 cm −1 (Δ ν NO =95 cm −1 ; Figure b), which was further corroborated by studies with isotope‐labeled 1‐ 15 NO (see Figure S6). Thus far, only one‐electron π‐ring oxidation of {Co(NO)} 8 cobalt–nitrosyl tetraaryl porphyrins provided an NO‐intact product with Δ ν NO ≈40 cm −1 ; all other reduction processes resulted in facile denitrosylation . Notably, the one‐electron electrochemical reduction of 1 only caused a redshift of the Soret‐like band from λ max =432 to 455 nm without significant peak broadening in the UV/Vis SEC spectra (Figure ).…”

Reflectance infrared and UV–visible spectroelectrochemical studies on a series of [Ni3(µ3-L)(µ3-I)(µ2-dppm)3][PF6] (L = CO; CNR, R = alkyl, aryl; dppm = Ph2PCH2PPh2) clusters

“…Infrared spectroelectrochemistry studies have been carried out on a number of organometallic systems and allow for the in situ monitoring of sensitive electrogenerated species (20)(21)(22)(23)(24)(25). The vibrational spectra so obtained allow for structural and electronic changes to be directly monitored.…”

Structure and Reactivity of NO/NO+/NO−Pincer and Porphyrin Complexes

“…[101] Even if the first oxidation is reversible in the voltammetric timescale, the second process eventually yields Co(III) species and free NO. [104,105,118,121] Interestingly, results from spectroelectrochemical studies in organic media showed changes in the ν NO frequency during the first and second oxidation that were consistent with formation of π cations on the porphyrin system still bearing the NO moiety. [102,121] On the other hand, reduction experiments ended in NO labilization after the first reductive process.…”

“…[104,105,118,121] Interestingly, results from spectroelectrochemical studies in organic media showed changes in the ν NO frequency during the first and second oxidation that were consistent with formation of π cations on the porphyrin system still bearing the NO moiety. [102,121] On the other hand, reduction experiments ended in NO labilization after the first reductive process. [121] Using a perbromated, nitrosubstituted porphyrin, Kadish and coworkers could relatively stabilize the one and two-electron reduction products, which conserved the NO moiety on a short timescale, suggesting a reduction process based on the electron withdrawing macrocycle.…”