Synthesis and characterization of a new 4-styrylpyridine based square planar copper(II) complex: exploration of phenoxazinone synthase-mimicking activity and DFT study

A new 4-styrylpyridine (4-spy)-based square planar copper(II) complex, [Cu(4-spy)2(NCS)2] {4-spy = 4-styrylpyridine} (1), has been synthesized and characterized by elemental analysis and single-crystal X-ray diffraction study. The complex crystallizes in triclinic space group Pī and forms square planar geometry. Complex 1 is self-assembled to construct 3D supramolecular architecture via π–π interactions. Complex 1 exhibits strong biomimetic phenoxazinone synthase-like activity under mild conditions for the aerial oxidation of o-aminophenol to amino phenoxazinone, i.e. modeling the catalytic function of the copper-containing enzyme phenoxazinone synthase. The turnover number (kcat) for the process in methanol is 50.13 × 10−2 s−1. The mechanism of phenoxazinone synthase-like activity has been proposed for the Cu(II) catalyst with the help of mass spectral analysis. Density functional theory study has also been explored to corroborate the experimental findings.