Abstract
The asymmetric unit of the title complex salt, [Cr(C10H24N4)(NH3)2][ZnCl4]Cl·H2O, is comprised of four halves of the Cr(III) complex cations (the counterparts being generated by application of inversion symmetry), two tetra-chlorido-zincate anions, two chloride anions and two water mol-ecules. Each Cr(III) ion is coordinated by the four N atoms of the cyclam (1,4,8,11-tetra-aza-cyclo-tetra-deca-ne) ligand in the equatorial plane and by two N atoms of ammine ligands in axial positions, displaying an overall distorted octa-hedral coordination environment. The Cr-N(cyclam) bond lengths range from 2.0501 (15) to 2.0615 (15) Å, while the Cr-(NH3) bond lengths range from 2.0976 (13) to 2.1062 (13) Å. The macrocyclic cyclam moieties adopt the trans-III conformation with six- and five-membered chelate rings in chair and gauche conformations. The [ZnCl4](2-) anions have a slightly distorted tetra-hedral shape. In the crystal, the Cl(-) anions link the complex cations, as well as the solvent water mol-ecules, through N-H⋯Cl and O-H⋯Cl hydrogen-bonding inter-actions. The supra-molecular set-up also includes N-H⋯Cl, C-H⋯Cl, N-H⋯O and O-H⋯Cl hydrogen bonding between N-H or C-H groups of cyclam, ammine N-H and water O-H donor groups, and O atoms of the water mol-ecules, Cl(-) anions or Cl atoms of the [ZnCl4](2-) anions as acceptors, leading to a three-dimensional network structure.
Highlights
The asymmetric unit of the title complex salt, [Cr(C10H24N4)(NH3)2][ZnCl4]ClH2O, is comprised of four halves of the CrIII complex cations, two tetrachloridozincate anions, two chloride anions and two water molecules
Each CrIII ion is coordinated by the four N atoms of the cyclam (1,4,8,11-tetraazacyclotetradecane) ligand in the equatorial plane and by two N atoms of ammine ligands in axial positions, displaying an overall distorted octahedral coordination environment
A deeper knowledge of the conformation and crystal packing of metal complexes containing the cyclam ligand has become important in the development of new highly effective anti-HIV drugs that specifially target alternative events in the HIV replicative cycle (De Clercq, 2010)
Summary
The cyclam macrocycle (1,4,8,11-tetraazacyclotetradecane, C10H24N4) can adopt both planar (trans) and folded (cis) configurations (Poon & Pun, 1980). There are five conformational trans isomers for the macrocycle, which differ in the chirality of the sec-NH groups (Choi, 2009). It has been reported that cyclam derivatives and their metal complexes exhibit anti-HIV activity (Ronconi & Sadler, 2007; De Clercq, 2010; Ross et al, 2012) whereby the strength of binding to the CXCR4 receptor correlates with the anti-HIV activity. A deeper knowledge of the conformation and crystal packing of metal complexes containing the cyclam ligand has become important in the development of new highly effective anti-HIV drugs that specifially target alternative events in the HIV replicative cycle (De Clercq, 2010). As part of a study on the structural and supramolecular features of chromium(III) complex cations with a macrocyclic ligand and with different anions, we report here the structural characterization of trans-[Cr(NH3)2(cyclam)][ZnCl4]ClH2O, (I)
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