Because of their versatile coordination modes and strong coordination ability for metals, triazole ligands can provide a wide range of possibilities for the construction of metal–organic frameworks. Three transition-metal complexes, namely bis(μ-1,2,4-triazol-4-ide-3-carboxylato)-κ3
N
2,O:N
1;κ3
N
1:N
2,O-bis[triamminenickel(II)] tetrahydrate, [Ni2(C3HN3O2)2(NH3)6]·4H2O, (I), catena-poly[[[diamminediaquacopper(II)]-μ-1,2,4-triazol-4-ide-3-carboxylato-κ3
N
1:N
4,O-[diamminecopper(II)]-μ-1,2,4-triazol-4-ide-3-carboxylato-κ3
N
4,O:N
1] dihydrate], {[Cu2(C3HN3O2)2(NH3)4(H2O)2]·2H2O}
n
, (II), (μ-5-amino-1,2,4-triazol-1-ide-3-carboxylato-κ2
N
1:N
2)di-μ-hydroxido-κ4
O:O-bis[triamminecobalt(III)] nitrate hydroxide trihydrate, [Co2(C3H2N4O2)(OH)2(NH3)6](NO3)(OH)·3H2O, (III), with different structural forms have been prepared by the reaction of transition metal salts, i.e. NiCl2, CuCl2 and Co(NO3)2, with 1,2,4-triazole-3-carboxylic acid or 3-amino-1,2,4-triazole-5-carboxylic acid hemihydrate in aqueous ammonia at room temperature. Compound (I) is a dinuclear complex. Extensive O—H...O, O—H...N and N—H...O hydrogen bonds and π–π stacking interactions between the centroids of the triazole rings contribute to the formation of the three-dimensional supramolecular structure. Compound (II) exhibits a one-dimensional chain structure, with O—H...O hydrogen bonds and weak O—H...N, N—H...O and C—H...O hydrogen bonds linking anions and lattice water molecules into the three-dimensional supramolecular structure. Compared with compound (I), compound (III) is a structurally different dinuclear complex. Extensive N—H...O, N—H...N, O—H...N and O—H...O hydrogen bonding occurs in the structure, leading to the formation of the three-dimensional supramolecular structure.
Disorder in the anionic part ofcatena-poly[[(pyrazine-2-carboxylato)copper(II)]-μ-pyrazine-2-carboxylato]