Solvent effect on neutral Co (II) complexes of paeonol derivative –qualitative and quantitative studies from energy frame work and Hirshfeld surface analysis

Abstract

Co (II) Complex of 1-(2-hydroxy-4-methoxyphenyl)ethanone has been synthesized and crystallized as solvates. The crystallization solvents used are β-picoline and pyridine. However, from β-picoline the metal complex crystallized without solvent as Co[(C9H9O3)]2(A) in monoclinic space group P21/c with lattice parameters a = 6.576(1)Ǻ, b = 11.6897(18)Ǻ, c = 10.8788 (17)Ǻ, β = 97.124 (2)° and Z = 4. From pyridine, complex crystallizes with two solvent molecules as Co[(C9H9O3)2(C5H5N)2](B) in the monoclinic space group C2/c with Z = 4 and lattice parameters as a = 17.698(2)Ǻ, b = 14.4312(16)Ǻ, c = 10.8803(12)Ǻ, and β = 116.94(2)°. In both unsolvated (A) and solvated (B) complexes Co occupies the special position (000). In solvated complex (B) the nitrogen (N1, N2) and carbon (C12, C15) of both the solvent pyridines lie on symmetry axis along with Co thereby generating other half of both the pyridines symmetrically. In unsolvated complex (A), molecular geometry around Co is distorted tetrahedral with Co coordinating to all four oxygens of bidentate ligand (Paeonol) forming a pseudo square planer configuration where as in the solvated complex (B) Co forms a pseudo square planer configuration along with nitrogens of the solvent pyridines occupying apexial position to complete the octahedral sphere. Similarities and differences in the molecular packing of unsolvated and solvated Co complex are established through the investigation of qualitative and quantitative contribution of intermolecular interactions using Hirshfeld surface and energy frame work analysis. The quantitative contributions of each intermolecular interaction towards molecular stability reveals comparatively higher value of energy (negative) for the solvated complex (B) than those of unsolvated complex (A) highlighting the significant contributions of solvent molecule in molecular stability.