Syntheses and structural characterizations of the first coordination polymers assembled from the Ni(cyclam)2+ cation and the benzene-1,3,5-tricarboxylate linker

Abstract

The asymmetric unit of catena-poly[[[(1,4,8,11-tetraazacyclotetradecane-κ4N1,N4,N8,N11)nickel(II)]-μ2-5-carboxybenzene-1,3-dicarboxylato-κ2O1:O3] octahydrate], {[Ni(C9H4O6)(C10H24N4)]·8H2O}n (I), consists of a macrocyclic Ni2+ cation, a carboxylate dianion and eight highly disordered water molecules of crystallization. The components of the compound catena-poly[[[(1,4,8,11-tetraazacyclotetradecane-κ4N1,N4,N8,N11)nickel(II)]-μ2-5-carboxybenzene-1,3-dicarboxylato-κ2O1:O3] monohydrate], {[Ni(C9H4O6)(C10H24N4)]·H2O}n (II), are two crystallographically unique centrosymmetric macrocyclic dications, a carboxylate dianion and one water molecule of crystallization. In each compound, the metal ion is coordinated in the equatorial plane by the four secondary N atoms of the macrocyclic ligand, which adopts the most energetically stable trans-III conformation, and two mutually trans O atoms of the carboxylate anions in a slightly tetragonally distorted trans-NiN4O2 octahedral geometry. The crystals of both compounds are composed of parallel coordination polymeric chains running along the [010] direction in I and the [110] and [1\overline{1}0] directions in II. The bridging carboxylate anions display different modes of coordination connected with the relative orientation of coordinated O atoms, i.e., remote in I and intermediate in II, thus resulting in essentially different distances between the Ni atoms in the chains [11.0657 (4) and 8.9089 (2) Å in I and II, respectively]. As a result of hydrogen-bonding interactions, the chains are joined together in sheets oriented parallel to the (10\overline{1}) and (001) planes in I and II, respectively.

Keywords

• crystal structure
• coordination polymers
• cyclam
• nickel
• benzenetricarboxylate
• hydrogen bonds