Penta-coordinated Cr(II) and Cu(II) complexes appended with 4′-(4-quinolyl)-2,2′:6′,2″-terpyridine: Crystal structure, Hirshfeld surface analysis, luminescence and thermal properties

Abstract

Two new chromium and copper complexes containing 4′-(4-quinolyl)-2,2′:6′,2′'-terpyridine (qtpy) have been synthesized and characterized using elemental analysis, IR and X-ray crystal structure determination. The reaction of CrCl3.6H2O with qtpy in presence of granulated zinc as a reducing agent has been resulted in the formation of the new terpyridine chromium(II) complex [Cr(qtpy)Cl2] (1). Moreover, the reaction of CuBr2 with qtpy affords the new complex [Cu(qtpy)Br2] (2). Recrystallization of 1 from DMF and recrystallization of 2 from DMSO yield the respective solvates, [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO), confirmed by X-ray single crystal analysis. The crystal structures of isostructural complexes [Cr(qtpy)Cl2].DMF (1.DMF) and [Cu(qtpy)Br2].2DMSO (2.2DMSO) reveal that chromium(II) and copper(II) adopt the penta-coordinated square pyramidal geometry in which Cr and Cu are coordinated by three nitrogen atoms of qtpy and two Cl- for 1.DMF, and two Br- for 2.2DMSO. As well, the crystal packings of complex 1.DMF, and 2.2DMSO clearly show the formation of supramolecular structures through C-H…X (X = N, O, halide) hydrogen bond interactions. The 3D Hirshfeld surface analysis and 2D fingerprint maps were used for quantitative mapping out of the intermolecular interactions for 1.DMF, and 2.2DMSO. Luminescence properties of 1 and 2 displayed the ligand-based π–π* emission bands in solution. Thermal properties of 1 and 2 show that they undergo thermal decomposition and the corresponding metal oxide formed in each case.