Synthesis and crystal structure determination of 0D-, 1D- and 3D-metal compounds of 4-(pyrid-4-yl)-1,2,4-triazole with zinc(II) and cadmium(II)

The potentially tritopic bridging ligand 4-(pyrid-4-yl)-1,2,4-triazole (pytz) reacts with cadmium(II) nitrate tetrahydrate, Cd(NO3)2·4H2O and sodium dicyanamide (Na-dca) to form the molecular complex [Cd(dca)2(κNpy-pytz)2(H2O)2] (1). The cadmium atom lies on a center of inversion and is coordinated in a slightly distorted octahedral geometry by the trans-oriented pytz ligands, dicyanamide anions and aqua ligands. The pytz ligand coordinates through the Npyridin atom to the metal atom. The molecular complexes are connected to a 3D supramolecular network by O–H···Ndca and O–H···Ntriazole hydrogen bonds. From zinc(II) bromide and pytz the compound 1D-[ZnBr2(μ-κNpy,Ntz-pytz)] (2) is obtained where the pytz-ligand bridges between the tetracoordinated zinc(II) atoms through coordination of its Npyridine- and Ntriazole-atoms. Adjacent chains are connected through C–H···Br and C–H···N hydrogen bonds to form a 3D supramolecular structure. Single crystals of 2 crystallize homochiral in the non-centrosymmetric space group P212121. The origin of the homochirality is the formation of hydrogen-bonded helices around the 21 screw axes with the same sense of rotation (left-handed or M in the investigated crystal). Cd(NO3)2·4H2O, pytz and sodium thiocyanate (NaSCN) give the framework 3D-[Cd(μ-SCN)2(μ-κNpy,Ntz-pytz)] (3). Parallel layers of 2D-{Cd(μ-SCN)2}-nets with distorted (6,3)-net topology are assembled by the bridging pytz-ligands into a 3D-structure. The pytz-ligand bridges between two cadmium atoms by Npyridine- and Ntriazole-coordination.