Coordination geometries of high-spin manganese(III) porphyrins and their synthetic intermediates

Abstract

This report contains recent results which help clarify previous ambiguities about some aspects of Mn(III) coordination chemistry.1 These results clearly demonstrate the expected formation of distorted octahedral complexes of high-spin Mn(III)-a result contrary to some published structural work.2 This distortion, which frequently manifests itself in the form of a tetragonal elongation, is probably responsible for the ready incorporation of Mn(III) into porphyrins.34 The results reported herein also tend to contradict to some extent those which report high-spin octahedral manganese(III) porphyrins containing a very tightly cotí) See, for instance, F. A. Cotton and G. Wilkinson, "Advanced

Crystal structures of manganese- and cobalt-substituted myoglobin in complex with NO and nitrite reveal unusual ligand conformations

“…In both compounds, the azide ligand is oriented towards the interior of the protein. The Mn III -N(azide) distance of 2.37 Å is longer than those observed in the model complexes (TPP)Mn III ðN À 3 Þ(MeOH) (2.176(9) Å ) [73], (TPP)Mn III ðN À 3 Þ (2.045 Å ) [83], and (Schiff base)Mn III ðN À 3 Þ (2.221(4) Å ) [84]. The coordinating atom of the azide ligand is 2.64 Å away from the N e atom of the distal His64 residue, indicative of a hydrogen-bonding stabilization of the azide ligand in the distal pocket.…”

Characterization of Mn(III)porphyrin immobilized on modified silica surfaces by EXAFS spectroscopy: A promising tool for analysis of supported metalloporphyrin catalysts

“…Even though is not possible to distinguish the origin of the oxygen atom by this EXAFS analysis, this Mn-O distance is found in the structure of [Mn(TPP)(H 2 O) 2 ]ClO 4 [29]. The solvent used for the immobilization of the complex on to the matrix surface was MeOH, then its presence as axial ligand cannot be ruled out, since in the reported XRD structure of [Mn(TPP)N 3 (CH 3 OH)] the Mn-O distance is 2.329Å [30]. As pointed by Maclean et al [13], the competition between the oxygen atoms from the support and from the solvent for the axial positions should not be excluded, although in our examples the anionic ligands will interact, most likely, with the cationic functional groups of the porphyrin ring.…”

Synthesis, Characterization and Antifungal Activities of Some Novel Mixed Ligand Complexes of Manganese(III) g-Diketone

“…This is supported the global research interests in the studies of Mn(III) complexes [8][9][10][11][12][13]. Wide variety of high spin Mn(III) octahedral complexes are reported in literature [14][15][16][17][18]. Manganese(III) β-diketone complexes shows versatile catalytic behaviour [19][20][21][22][23][24] and are also used in the depolymerization of coal using humic acid, as a coal model compound [23] which has been tested by viscosity measurement method.…”