Two new Cr(III) (C1) and Fe(III) (C2) complexes incorporating 2,6-pyridinedicarboxylic acid (PDC) and 2-methyl-1H-benzimidazole (MB): Synthesis, structure, DFT and phenoxazinone synthase mimicking activity.

• New mixed ligand complexes of Cr(III) (C1) & Fe(III) (C2) were synthesized and characterized. • The isolated complexes exhibited a ratio of 1:1:1 (M: MB: PDC). • The C1 and C2 complexes displayed activity potential to the phenoxazinone synthase mimicking. • The observed complexes had a high turnover number (k cat), compared to previously reported ones, suggesting their potential activity to the catalytic function of phenoxazinone synthase. The current study included the synthesis and characterization of newly mixed ligand complexes of Cr(III) (C1) & Fe(III) (C2) incorporating 2,6-pyridinedicarboxylic acid (PDC) and 2-methyl-1H-benzimidazole (MB). The isolated complexes exhibited a ratio of 1:1:1 (M:MB:PDC), indicating the existence of an octahedral configuration centered on the Cr(III) and Fe(III) core, as denoted by the chemical formula [M(MB)(PDC)(Cl)(H 2 O)]. The determination of the most stable coordination modes, trans/cis orientations of the water/chloride ligands, was achieved using theoretical calculations employing density functional theory (DFT). The purpose of these computations was the investigation of the two different trans/cis orientations of the water/chloride around the Cr(III)/Fe(III) center. The complexes were analyzed using DFT to optimize their geometrical properties, characterize their molecular orbitals, and determine the energies associated with the trans/cis coordination approaches of water/chloride around the Cr(III)/Fe(III) center. The trans-water/chloride around the Cr(III)/Fe(III) was found to be the most preferred coordination mode. The C1 and C2 complexes displayed activity potential to the phenoxazinone synthase mimicking through the aerial coupling of o-aminophenol (OAPh) to phenoxazine-2-one (phenox). The Michaelis-Menten enzymatic kinetics was used for the quantification of the mimicking activity. Various enzyme kinetics plots were used to measure a range of kinetic characteristics, such as the specificity constant and turnover number (k cat), as part of comprehensive evaluations of the catalytic cycles. The observed complexes had a high turnover number (k cat), compared to previously reported ones, suggesting their potential activity to the catalytic function of phenoxazinone synthase. [Display omitted] [ABSTRACT FROM AUTHOR]