Metal–organic supramolecular architecture of oxo-bridged molybdenum(VI) complexes: Synthesis, structural elucidation and Hirshfeld surface analysis

Abstract

New Binuclear monooxo, Mo2O4L21(H2O)CHCl3 (1), tetranuclear tetraoxo, Mo4O8L41 (2) and binuclear dioxo, Mo2O4L22 (3) bridged molybdenum(VI) complexes have been synthesized using two diprotic tridentate ONS donor Schiff base ligands H2L1 and H2L2 (H2L1 = S-benzyl-β-N-(2-hydroxyphenyl) methylene dithiocarbazate and H2L2 = S-benzyl-β-N-(5‑bromo-2-hydroxyphenyl) methylene dithiocarbazate. All the three complexes have been characterized by elemental analyses and IR, UV–vis and 1H NMR spectroscopies and their crystal structures were solved by single crystal X-ray diffraction technique. Complexes (1) and (3) crystallized in triclinic space group P-1 and complex (2) in monoclinic space group P21/n. Complexes 1, 2 and 3 exhibit distorted octahedral geometry around Mo(VI) center. X-ray crystallography reveals that in the crystal packing of the complexes C–H···O, O–H···O, O–H···N, C–X···π (X = Br) and π···π stacking interactions cooperatively take part. A detailed analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions which are crucial in building different supramolecular architectures of three molybdenum complexes. Crystal structure analysis supported with the Hirshfeld surface and fingerprint plots enabled the identification of the significant intermolecular interactions. The intermolecular interactions are further characterized by analyzing the topological parameters through Bader's theory of ‘atoms in molecule’ (QTAIM) along with the ‘non-covalent interaction’ (NCI) plot index. The investigation of topological parameters of electron density at the (3, −1) bond critical point classified the interactions as ‘closed-shell’ interactions.