Synthesis, spectroscopic properties, structural characterization, and computational studies of a new non-centrosymmetric hybrid compound: bis-cyanato-N chromium(iii) meso-arylporphyrin complex

Abstract

In this work, we report the synthesis and spectroscopic properties of a hexa-coordinated chromium(III) porphyrin complex, namely, bis(cyanato-N)[meso-tetraphenylporphyrinato]chromate(III) (cryptand-222)sodium chloroform monosolvate with the formula [Na(2,2,2-crypt)][Cr^III(TPP)(NCO)₂]·0.406CHCl₃ (I). Complex I was characterized in solution by UV/vis and IR spectroscopies. The structural determination of compound I was performed by single-crystal X-ray diffraction and Hirshfeld surface area calculations. This compound crystallized in the triclinic system with the non-centrosymmetric space group P1. The average distance between the central Cr(III) ion and the nitrogen atoms in the equatorial position is 2.039(3) Å, while the Cr^III–N (axial ligand) distances from the bis-cyanate ligand are 2.012(3) Å and 2.016(4) Å. Crystal packing cohesion was stabilized by unconventional intramolecular C–H⋯O and C–H⋯Cl hydrogen bonds. In addition, we conducted a theoretical investigation of several key physical properties to provide a comprehensive understanding of the electron charge transfer mechanisms of the chromium(III) porphyrin complex using density functional theory (DFT) at the B3LYP-D3/LanL2DZ level. This includes the analysis of frontier molecular orbitals (FMOs) and associated reactivity descriptors; molecular electrostatic potential (MEP) assessment; non-covalent interaction (NCI) analysis through reduced density gradient (RDG) surfaces and bond critical points (BCPs); as well as electron localization function (ELF), localized orbital locator (LOL), and Hirshfeld surface analyses.