Novel structures based on 1-(4-cyanophenyl)-imidazole resulting from weak bonding interactions

Mono-nuclear complexes [M(CPI)6](X)2 (M = Co, X = NO3−1; M = Ni, X = NO3−2; M = Cu, X = ClO4−3) and [Cu(CPI)4(H2O)2](NO3)24, based on novel bridging ligand 1-(4-cyanophenyl)-imidazole (CPI) are reported. The complexes have been characterized by elemental analyses, spectral studies and their molecular structures have been authenticated by single crystal X-ray diffraction analyses. In molecular species 1–3 metal centers are coordinated octahedrally by six CPI ligands wherein cyanophenyl rings of six ligands about the complex cations are involved in face-to-face π–π interaction with six co-planar molecules to afford unprecedented 2D sheet. Along ‘c’-axis it gives a beautiful rim like motif. In complex 4, coordination about metal center Cu is distorted octahedral with four CPI ligands in the equatorial position and two water molecules occupying axial positions. In this complex hydrogen bonding interactions between the coordinated water molecules and nitrate anions results in a 1D straight chain along ‘a’-axis and 2D sheets having hexagonal cavity filled by nitrate ions. The complexes upon excitation at 275–285 nm exhibit luminescences with emission maxima centered at 438–445 nm attributable to the ligand CPI at room temperature.