One-pot cocrystallization of mononuclear and 1D cobalt(II) complexes based on flexible triclopyr and 2,2′-bipyridine coligands: Structural analyses, conformation comparison, non-covalent interactions and magnetic properties

Abstract

A pair of cobalt(II) complexes with formulas of [Co(3,5,6-tcpa)(2,2′-bpy)Cl] (1A) and [Co(3,5,6-tcpa)2(2,2′-bpy)]n (1B) have been cocrystallized by the solvothermal reaction of cobalt chloride hexahydrate with triclopyr (systematic name 2-((3,5,6-trichloropyridin-2-yl) oxy)acetic acid, abbreviation 3,5,6-Htcpa) and 2,2′-bipyridine (2,2′-bpy). Single-crystal X-ray diffraction analysis indicated that both 1A and 1B crystallized in triclinic system, space group P1¯ (no. 2). Compound 1A is mononuclear and 3,5,6-tcpa anion in it is a bidentate chelate ligand. In contrast, 1B is a 1D double-stranded chain structure in which 3,5,6-tcpa are bidentate bridging-μ2 linkers. The non-covalent interactions of Cl···Cl halogen bonds, C–H···O/Cl hydrogen bonds as well as π···π stacking interactions play an important part in their crystal packing, which have been confirmed by the careful Hirshfeld surface analyses. After deeply structural analyses, it was proposed that flexible conformation alteration of 3,5,6-tcpa might be in charge of the cocrystallization phenomenon of 1A and 1B. In addition, the magnetic characterizations suggested antiferromagnetic coupling between neighbouring cobalt(II) centers in 1B.