1D-Coordination Polymer of Copper(I) thiocyanate complex with metronidazole: Synthesis, crystal structure, Hirshfeld surface analysis, PXRD, Spectroscopic properties, MEP, QTAIM, π(CN)···tetrel interaction, RDG, and thermal analysis

Abstract

Within 24 h of slow evaporation of the solution containing CuCl2·2H2O, metronidazole, and NH4SCN, a red-like crystalline Cu(I) complex titled [Cu(SCN)(mnz)]n (1), [where mnz = metronidazole; SCN = thiocyanate], was synthesized. The presence of SCN− during the synthesis induces reduction of the Cu(II) to Cu(I) giving rise to novel 1D coordination polymer. The compound was characterized by single crystal X-ray diffraction, powdered X-ray diffraction, spectroscopic proprieties, and Hirshfeld surface analysis. [Cu(SCN)(mnz)]n crystallizes in the monoclinic space group P21/c. The complex possesses a 1D layer structure constructed by linking the staircase-like [CuSCN]n chains. Intermolecular interactions in the crystals investigation via Hirshfeld surface analysis reveals the major contribution is from O···H/H···O interaction (22.9 %), which is due to the presence of hydrogen bonds of the O − H···O type. The thermal properties were investigated using DTA-TGA and DSC. The study comprises the interpretation of non-covalent interactions through Quantum Theory of Atoms in Molecules (QTAIM), Natural Bond Orbital (NBO) analyses, and Reduced Density Gradient (RDG). The results show the role of interactions between SCN− and mnz through multiple connections involving the oxygen, nitrogen, and sulfur lone pairs and π-bonds for constructing the unit cell. The non-covalent arrangements include very weak hydrogen bonds that cooperatively stabilize the crystal. Along with SCN− bridging copper atoms, growth in the ab plane is favored by an uncommon π···π interaction between SCN− and the imidazole ring of mnz. In this interaction, the π(SN) and π(CN) orbitals perturb the imidazole π(CN) orbital with energies of 0.36 and 0.22 kcal/mol, respectively. In the c direction, a hydrogen bond between the hydroxyl group and CH- fragment from different mnz molecules assists structure stabilization. It is accompanied by a rarely observed π(CN)···tetrel interaction, wherein SCN− donates π-electron density to the antibonding σ(CH) orbital of the methyl carbon.