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Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

ABSTRACT: The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl(-) and H2O around Zn(2+). According to the solid-liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn(2+) both in a tetra-hedral coordination with Cl(-) and in an octa-hedral environment defined by five water mol-ecules and one Cl(-) shared with the [ZnCl4](2-) unit. Thus, these two different types of Zn(2+) cations form isolated units with composition [Zn2Cl4(H2O)5] (penta-aqua-?-chlorido-tri-chlorido-di-zinc). The trihydrate {hexa-aqua-zinc tetra-chlorido-zinc, [Zn(H2O)6][ZnCl4]}, consists of three different Zn(2+) cations, one of which is tetra-hedrally coordinated by four Cl(-) anions. The two other Zn(2+) cations are each located on an inversion centre and are octa-hedrally surrounded by water mol-ecules. The [ZnCl4] tetra-hedra and [Zn(H2O)6] octa-hedra are arranged in alternating rows parallel to [001]. The structure of the 4.5-hydrate {hexa-aqua-zinc tetra-chlorido-zinc trihydrate, [Zn(H2O)6][ZnCl4]·3H2O}, consists of isolated octa-hedral [Zn(H2O)6] and tetra-hedral [ZnCl4] units, as well as additional lattice water mol-ecules. O-H?O hydrogen bonds between the water mol-ecules as donor and ZnCl4 tetra-hedra and water mol-ecules as acceptor groups leads to the formation of a three-dimensional network in each of the three structures.

SUBMITTER: Hennings E

PROVIDER: S-EPMC4257420 | biostudies-literature | 2014 Dec

REPOSITORIES: biostudies-literature

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Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

Hennings Erik E Schmidt Horst H Voigt Wolfgang W

Acta crystallographica. Section E, Structure reports online 20141115 Pt 12

The formation of different complexes in aqueous solutions is an important step in understanding the behavior of zinc chloride in water. The structure of concentrated ZnCl2 solutions is governed by coordination competition of Cl(-) and H2O around Zn(2+). According to the solid-liquid phase diagram, the title compounds were crystallized below room temperature. The structure of ZnCl2·2.5H2O contains Zn(2+) both in a tetra-hedral coordination with Cl(-) and in an octa-hedral environment defined by f ...[more]

PMID: 25552980

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Project description:Bedaquiline [systematic name: 1-(6-bromo-2-methoxyquinolin-3-yl)-4-(dimethylamino)-2-(naphthalen-1-yl)-1-phenylbutan-2-ol, C32H31BrN2O2] is one of two important new drugs for the treatment of drug-resistant tuberculosis (TB). It is marketed in the US as its fumarate salt {systematic name: [4-(6-bromo-2-methoxyquinolin-3-yl)-3-hydroxy-3-(naphthalen-1-yl)-4-phenylbutyl]dimethylazanium 3-carboxyprop-2-enoate, C32H32BrN2O2+·C4H3O4-}, and about a dozen other salts of bedaquiline have been described in patent literature, but none have so far been structurally described. In a first communication, we present the crystal structure of bedaquilinium fumarate and of two new benzoate salts, as well as that of a degradation product of the reaction of bedaquilinium fumarate with sodium ethoxide, 3-benzyl-6-bromo-2-methoxyquinoline, C17H14BrNO. The fumarate and benzoate salts both feature cations monoprotonated at the dimethylamino group. The much less basic quinoline N atom remains unprotonated. Both salts feature a 1:1 cation-to-anion ratio, with the fumarate being present as monoanionic hydrofumarate. The conformations of the cations are compared to that of free base bedaquiline and with each other. The flexible backbone of the bedaquiline structure leads to a landscape of conformations with little commonalities between the bedaquiline entities in the various structures. The conformations are distinctively different for the two independent molecules of the free base, the two independent molecules of the hydrofumarate salt, and the one unique cation of the benzoate salt. Packing of the salts is dominated by hydrogen bonding. Hydrogen-bonding motifs, as well as the larger hydrogen-bonded entities within the salts, are quite similar for the salts, despite the vastly differing conformations of the cations, and both the hydrofumarate and the benzoate structure feature chains of hydrogen-bonded anions that are surrounded by and hydrogen bonded to the larger bedaquilinium cations, leading to infinite broad ribbons of anions, cations, and (for the benzoate salt) water molecules. The benzoate salt was isolated in two forms: as a 1.17-hydrate (C32H32BrN2O2+·C7H5O2-·1.166H2O), obtained from acetone or propanol solution, with one fully occupied water molecule tightly integrated into the hydrogen-bonding network of anions and cations, and one partially occupied water molecule [refined occupancy 16.6 (7)%], only loosely hydrogen bonded to the quinoline N atom. The second form is an acetonitrile solvate (C32H32BrN2O2+·C7H5O2-·0.742CH3CN·H2O), in which the partially occupied water molecule is replaced by a 74.2 (7)%-occupied acetonitrile molecule. The partial occupancy induces disorder for the benzoate phenyl ring. The acetonitrile solvate is unstable in atmosphere and converts into a form not distinguishable by powder XRD from the 1.17-hydrate.

Dataset Information

Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

Publications

Crystal structures of ZnCl2·2.5H2O, ZnCl2·3H2O and ZnCl2·4.5H2O.

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