Mononuclear manganese(iii) complexes with reduced imino nitroxide radicals by single-electron transfer and intermolecular hydrogen bonds as an intramolecular structural driving force

Abstract

One-electron transfer from Mn(ii) ions to an imino nitroxide radical gives mononuclear Mn(iii) complexes of the reduced amino imine-oxide form for which crystal structures evidence hydrogen bonds networks acting as a stabilizing driving-force.

Hypersensitive pressure-dependence of the conversion temperature of hysteretic valence tautomeric manganese–nitronyl nitroxide radical 2D-frameworks

“…The Raman spectrum at atmospheric pressure shows a peak at 1564 cm À1 (B), previously assigned to the n(O-NQC) elongation of the nitronyl ring. 17,23 As expected, this peak vanishes with increasing pressure and a new peak appears at 1600 cm À1 for P 4 0.19 GPa. It broadens at higher pressures, particularly for P 4 2.5 GPa.…”

“…It broadens at higher pressures, particularly for P 4 2.5 GPa. The peak around 1440 cm À1 (A), assigned to n(C-N) of the imidazole, 23 is broadening with increasing pressure but does not show any shift, as this vibrational mode is not affected by the VT transition. Pressure is known to induce Fig.…”

Mimicking of Tunichlorin: Deciphering the Importance of a β-Hydroxyl Substituent on Boosting the Hydrogen Evolution Reaction

“…The Q-band (34 GHz) EPR spectrum recorded at 25 K for the product [ 6 ] 2– resulting from the treatment of 6 with 0.5–2.5 equiv of Co­(Cp*) 2 (Figure c) contains a major signal with g = 2.006 that is best described as that of an anion radical with a spin population primarily located on the ligand, consistent with the spectroelectrochemical study of [ 6 ] 2– . Reductive processes of metalloporphyrins have been ascribed to both innocent and noninnocent ligand chemistry, and the clear distinction between ligand- and metal-centered reductions is frequently difficult . There is, however, a small additional signal with a well resolved rhombic g = [2.210, 2.106, 2.055] that may be assigned to a Ni­(I) species with a d x 2 – y 2 ground state, indicating the noninnocence of the ligand (Figure S32).…”

“…Thus, we proposed that the β-OH moiety induces the formation of a hydrogen bond network, which helps to stabilize one-electron reduced species and deliver the protons via a proton relay mechanism. 49 It is noteworthy that the hydrogen bond network also lowers the second electron reduction potential from 0.59 to 0.52 eV according to DFT calculations, and the HOMO−SOMO−LUMO plots illustrate the reduced species Thus, we proposed the catalytic mechanism for HER of 6 in the presence of water, as shown in Figure 10. As water is a much weaker acid compared to TsOH, water could be the proton acceptor, allowing TsOH to transfer the proton to form a hydrate proton.…”

“…Reductive processes of metalloporphyrins have been ascribed to both innocent and noninnocent ligand chemistry, and the clear distinction between ligand-and metal-centered reductions is frequently difficult. 49 There is, however, a small additional signal with a well resolved rhombic g = [2.210, 2.106, 2.055] that may be assigned to a Ni(I) species with a d x 2 −y 2 ground state, indicating the noninnocence of the ligand (Figure S32).…”