Crystal Structure of 1-(m-Chlorophenyl)biguanide Hydrochloride

Abstract

These interactions have also been suggested based on preliminary studies using NG-108-15 cell membranes, which showed that the rate of dissociation of the 5-HT3 receptor antagonist [ 3 H]RS-42358 depends upon the ligand used to prevent rebinding. 2 To characterize further putative allosteric interactions at 5-HT3 receptors, steady-state and kinetic radioligand binding studies have been conducted using the receptor agonist 1-(mchlorophenyl)biguanide. This suggests that the binding of this agonists to unoccupied sites on the receptor can increase the receptor's affinity for prebound ligands, and thereby slow their dissociation. 3,4 In this paper, we describe an X-ray structure determination of 1-(m-chlorophenyl)biguanide hydrochloride. The crystals were prepared from a commercially available compound.X-ray data for crystals of the title compound were collected by graphite-monochromatized Mo Kα radiation at 293 K. No absorption correction was applied. The structure was solved by direct methods and refined by full-matrix least-squares with anisotropic temperature factors for the non-hydrogen atoms. In both molecules, the C4, C5 atoms of the phenyl rings show relatively high temperature factors, which may be due to a localized molecular disorder. The hydrogen atoms bonded to C C8H11Cl2 N5 is monoclinic, P21/n. The unit-cell dimensions at 293 K are a = 9.3569(9), b = 13.6832(14), c = 18.4879(19)Å, β = 98.411(2)˚, V = 2341.6(4)Å 3 , Dx = 1.408 g/cm 3 , and Z = 8. The R value is 0.043 for 4129 reflections. The monoclinic unit cell contains two crystallographic independent molecules, A and B. The Cl(1) and Cl(4) ions are coordinated to 5 and 6 N atoms, respectively. In the crystal, there are two hydrogen bonds between N5A and N3B:N5B and N3A of the neighboring molecules, and constitute the major intermolecular attraction and packing force. These two molecules make a centro-symmetric dimer.

A practical guide to arylbiguanides — Synthesis and structural characterization

“…It is noteworthy that the cation can be represented by localized structure 8 and its resonance hybrids, whereas alternatives in which the central nitrogen atom is protonated (9) or an intramolecular hydrogen bond is formed (10) are not favored in the solid state. Similar observations have been made in all previous structural studies of biguanidinium cations (25,26,(28)(29)(30)(31)(32)(33)(34)(36)(37)(38), so protonation of biguanides to give struc- ture 8 appears to be a fundamental preference, both in the solid state and in solution (2). The two guanidinium subunits that can be considered to make up the biguanidinium cation lie in two distinct planes that form an angle of 22.8(4)°.…”

“…single hydrogen bond. Similar interactions between biguanidinium ions and halide have been observed previously (25,28,31,34,(36)(37)(38). In addition, the phenyl groups of each biguanidinium cation engage in multiple aromatic contacts or interactions with phenyl groups provided by neighboring cations (Fig.…”

“…The biguanidinium ions do not interact directly with each other by forming hydrogen bonds. The absence of inter-cationic hydrogen bonds has been noted in most other biguanidinium salts (28,29,31,34,(36)(37)(38), but they are nevertheless present in certain cases (25,26,32). Each chloride ion accepts a total of six hydrogen bonds from four neighboring biguanidinium cations (Fig.…”

“…Few structures of simple biguanidinium salts or biguanides have been reported (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38), and in none of these cases have aryl groups been present at positions 1 and 5. As a result, we elected to determine the structures of 1,5-diphenylbiguanide (6a) and its monohydrochloride salt.…”

Hydrogen-bonded networks in crystals built from bis(biguanides) and their salts

“…3a). The NLN distance in these cationic pairs is 3.033(3) Å. Intercationic hydrogen bonding is inhibited by coulombic repulsion and is absent in most biguanidinium salts (4,11,14,15,17,(19)(20)(21), although it has previously been observed in a few cases (12,13,18). Slightly offset face-to-face aromatic interactions are also observed in the structure of salt 2·2HCl (Fig.…”