Cooperative H-bonds, π⋯π and anion⋯π interactions as driving forces in the construction of novel Cu(II) bis(imidazol-2-yl) supramolecular 3D frameworks

Abstract

Two new Cu(II) complexes with bis(2-imidazolyl) based ligands, with the formula [Cu(BIM)2(SCN)2]·2H2O (BIM = bis(2-imidazol-2-yl)methane) and [Cu(HBIMAM)2(OH2)2](BF4)4·2H2O (BIMAM = bis(2-imidazol-2-yl)methylaminomethane) have been synthesized and characterized. Both compounds contain mononuclear entities as molecular building blocks (MBBs); neutral [Cu(BIM)2(SCN)2] in compound 1 and cationic [Cu(HBIMAM)2(OH2)2]4+ in compound 2. The coordination around the metal atoms shows a tetragonally-elongated octahedral geometry (CuN4S2 and CuN4O2 chromophores). The Q-band EPR spectra of both compounds are indicative of an essentially dx2-y2 ground state for copper(II) ions. The analysis of the crystal structures of both compounds shows a cooperative relationship between conventional hydrogen bonds and other non-covalent interactions. Thus, in compound 1 concerted π⋯π interactions are the driving force in the construction of one-dimensional frameworks, which are connected through H-bonds to give 3D structure. On the other hand, in compound 2, cooperative XH⋯F (X = N, O) H-bonds and anion⋯π interactions control the arrangement of the supramolecular 3D framework.