Anion-directed assembly of two fluorescent Cd(II) coordination polymers with a versatile multidentate N-donor building block 3-(2-pyridyl)-4,5-bis(4-pyridyl)-1,2,4-triazole

Assembly of Cd(II) nitrate with a novel tripyridyltriazole building block 3-(2-pyridyl)-4,5-bis(4-pyridyl)-1,2,4-triazole (L1) and pseudohalide anion dicyanamide (dca) or azide (N3) yields two coordination polymers {[Cd(L1)2(dca)2](H2O)2}n (1) and {[Cd2(L1)(μ1,1-N3)2(μ1,3-N3)(N3)](H2O)1.5}n (2). Single crystal X-ray diffraction analysis indicates that the Cd(II) centers in 1 are bridged by the bidentate L1 ligands to form 1D arrays, which are further extended to a 3D network via hydrogen bonding and aromatic stacking. Significantly, the L1 ligands in 2 display the unusual pentadentate coordination and the azide anions take different μ1,1-, μ1,3-, and unidentate binding modes, interlinking the Cd(II) ions to afford a complicated 3D open framework with the inclusion of lattice water guests. Both complexes exhibit strong solid state fluorescent emissions at room temperature.