Catechol oxidase and phenoxazinone synthase mimicking activity, X‐ray diffraction and density function theory study of pyridine and phenolate‐based manganese(II) and iron(III) complexes: Synthesis and spectroscopic characterization

Abstract

A new series of MnII and FeIII chelates containing pyridine and phenolate‐based ligands was synthesized by treating the metal salt in ethanol with the Schiff‐bases, which were formed in situ. Analytical (C, H, N, and M), thermal analysis (thermogravimetric analysis & differential thermogravimetric), and spectroscopic techniques (IR, UV–Vis, ESR) in addition to molar conductance and magnetic measurements were employed to characterize the prepared metal chelates. Mono‐nuclear metal complexes, with N5 donor containing pentadentate Schiff‐base ligands were obtained. In addition, two dibridged homobinuclear iron(III) complexes with N4O donors containing phenolate‐based ligand were successfully isolated. Six‐coordinate complex species in an octahedral environment is proposed for both MnII and FeIII metal complexes. The density function theory study was used to optimize the geometrical shapes of three of the existing metal complexes and to identify some global reactivity descriptors. In addition, spectral data of PXRD with Expo 2014's structural solution software were utilized in the structural illustration of a representative MnII and FeIII complexes. Aerobic catalytic oxidation of 4‐tert‐butylcatechol (4‐TBCH2) and o‐aminophenol under catalytic conditions was studied by using the present manganese(II) and iron(III) complexes. The synthesized MnII and FeIII chelates exhibited a promising catalytic activity and probable catalytic sequences have been discussed.

Structural and bio-catalytic aspects of nano crystallite iron(iii) complexes containing triazole-based ligands

“…Nowadays, XRD data processing of microcrystalline samples of metallic complexes by Expo 2014 combined with Rietveld's method 55 has become an alternative technique for X-ray single crystal structural analysis. 7,26,27,56…”

“…The computed values (Table 6) of cell dimensions such as a , b and c in Å and α , β and γ in (°), cell volume (Å 3 ), density (g cm −3 ) and Rietveld results are acceptable and comparable with those reported for similar cases. 7,26,27,56…”

“…Nowadays, XRD data processing of microcrystalline samples of metallic complexes by Expo 2014 combined with Rietveld's method 55 has become an alternative technique for X-ray single crystal structural analysis. 7,26,27,56 Fig. 4 shows the X-ray powder diffraction spectrum of complex 1 while the spectra of the other complexes 2 and 3 are given in S26 and S31 (ESI †).…”

“…The computed values (Table 6) of cell dimensions such as a, b and c in Å and a, b and g in ( 1), cell volume (Å 3 ), density (g cm À3 ) and Rietveld results are acceptable and comparable with those reported for similar cases. 7,26,27,56 Looking at the numbering diagrams in Fig. 6(a,b), 8 and 9 it becomes clear that the iron(III) centers of the mono nuclear complex 2 and binuclear complexes 1 and 3 are geometrically similar.…”

“…6 Oxidation mimicking studies using iron(III) complexes showed selective catalytic oxidation of catechol because it oxidized catechol to ortho quinone instead of ring-breaking. [7][8][9][10][11][12][13][14][15] Several studies have reported the catalytic activity of iron complexes for the selective oxidation of o-aminophenols to produce the pharmaceutically important amino-3-H-phenoxazin-3-one (APX) instead of ring-opening. [16][17][18][19][20][21][22][23][24] The current study aims to gain a deeper understanding of the natural process of metal ions as catalysts and gain experience in designing more efficient catalysts.…”