Influence of the Electrochemical Conversion of [(LH)Mn^IICl₂] into [(L)Mn^IIICl]⁺on the Protonic State of a Phenol-Containing Ligand

Abstract

A bischloromanganese(II) complex [(LH)MnCl2] (1), where LH is the pentadentate ligand N,N-bis(2-pyridylmethyl)-N'-salicylidene- ethane-1,2-diamine, has been synthesized. Elemental analysis, UV-visible, and cyclic voltammetry experiments showed that the phenol function of the ligand LH remains protonated. Exhaustive electrolysis at 1.0 V vs SCE led to the formation of the Mn(III) derivative [(L)MnCl]+ (3) with the concomitant expulsion of H+ and Cl-. The formation of the Mn(III) species was confirmed by UV-visible spectroscopy and X-ray crystallography. Complex 1 could be regenerated by the reduction of complex 3 in the presence of H+ and Cl-.

Stabilization of Mn(II) and Mn(III) in mononuclear complexes derived from tridentate ligands with N2O donors: Synthesis, crystal structure, superoxide dismutase activity and DNA interaction studies

“…However, another redox wave detected at E 1/2 =0.80-1.06 V vs. Ag/AgCl is described as Mn(III)/Mn(IV) redox couple. These data match with the values reported [20,58,64] for the manganese complexes with similar ligand frame. E 1/2 values for Mn(II)/Mn(III) and Mn(III)/Mn(IV) couples in 5 are 0.143 V and 0.802 V respectively.…”

“…Mn-N imine distance 2.2984(17) Å is also closely related with reported data[56,58,59]. The MnN 4 O 2 coordination shows a considerable distortion because of ligand's rigidity.…”

“…Similarly Mn-O phenolato , Table 2) which differ significantly from ideal 90°and 180°. In complex 2, Mn-N py [58] and other structurally characterized manganese(III) complexes [21,48,61,62]. A d 4 system of manganese(III) is susceptible to undergo Jahn-Teller distortion and is expected to show elongation of trans bonds.…”

Chemical and Electrochemical Behaviours of a New Phenolato‐Bridged Complex [(L)MnIIMnII(L)]2+. Pathways to Mononuclear Chlorido [(L)MnII/III/IVCl]0/1/2+ and Dinuclear Mono‐µ‐Oxido [(L)MnIII(µ‐O)MnIII/IV(L)]2+/3+ Species

“…Research along this field is being pursued in our laboratory. Recently, we have reported on the metalation of the ligand LH, where LH is the [N 4 O] phenol‐containing ligand N , N ‐bis(2‐pyridylmethyl)‐ N′ ‐salicylidene‐ethane‐1,2‐diamine, with Mn II salt giving the [(LH)MnCl 2 ] complex where the phenol was still in a protonated state 24. We have shown through various spectroscopic characterizations that upon the first one‐electron oxidation process a concerted chemical reaction took place with the concomitant expulsion of one chloride ion from the manganese coordination sphere together with the deprotonation of the phenol and the coordination of the phenolate group.…”

Role of carboxamido nitrogen in mononuclear manganese complex: Superoxide scavenging activity and nuclease activity

“…In complex 3ÁCH 3 OH, Mn(III)-N am distances were longer than the reported distances, 1.9133(11) Å [12] and 1.922(4) or 1.945(3) Å [17]. In 3ÁCH 3 OH, Mn(III)-N py distances are usually shorter than reported Mn(III)-N Py distances [10,12,22]. The elongation of the trans Mn(III)-N am bonds and contraction of Mn-N Py bonds may be due to Jahn-Teller effect for a high-spin d 4 electronic configuration similar to [Mn III (Phimp) 2 ](ClO 4 ) [10,23].…”