Coordination Polymers Built with a Linear Bis-Imidazole and Different Dicarboxylates: Unusual Entanglement and Emission Properties

The linear linker bis(4-imidazol-1-ylphenyl)diazene (L) has been used to construct eight new coordination polymers with Zn(II), Cd(II) and Co(II) metal ions and different carboxylate donor ligands, viz., 1,1'-ferrocenedicarboxylic acid (H(2)Fc), 2',5'-dimethylterphenyl-4,4 ''-dicarboxylic acid (H(2)MDA), diphenic acid (H(2)DPA), biphenyl-4,4'-dicarboxylic acid (H2BIPH), 4,4'-oxybis (benzoic acid) (H2BIOXY), L-(-)-malic acid (H(3)LMA) and 2,2'-dibromo-6,6'-dinitrobiphenyl-4,4'-dicarboxylic acid (H(2)DBDPA). Compounds formed solvothermally are {[Cd(L)(Fc)-(H2O)]center dot(H2O)(2)}(n) (1), {[Cd(L)(MDA)]center dot DMF center dot CH3OH}(n) (2), {[Zn(L)- (M D A)] center dot 3H(2)O} (3)) {[Cd(L)(DPA)]}(n) (4), {[Cd-2(L)(2)(BIPH)(2)(H2O)(2)]center dot H2O}(n) (5), {[Cd-2(L)(2)(BIOXY)(2)]center dot H2O center dot CH3OH}(n) (6), {[Zn-3(L)(5)(LMA)(2)]center dot 2.5H(2)O}(n) (7) and {[Co(L)(DBDPA)center dot H2O}(n) (8). All the complexes have been characterized by single crystal X-ray diffraction, IR spectroscopy, thermogravimetry, elemental analysis and powder X-ray diffraction (PXRD). Interestingly, all complexes topologically exhibit 4-connected net except complex 7, which is (4,6). Moreover, the degree of interpenetration varies in 1-8. Complexes 1, 4 and 6 exhibit commonly occurring sql topology, while complexes 2 and 3 are 8-fold interpenetrated dia net. Contrary to this, complexes 5 and 8 show rare cdl and dmp nets with three and five mutual interpenetrative nets, respectively. However, 7 forms a novel pkb6 topological net with 2-fold interpenetration. Upon excitation at 322 nm, complexes 1-8 exhibit solid-state luminescence at room temperature.