Dual Chlorine-Bifurcated Acceptor Cl···H–(N,O) Hydrogen Bonds in 4-[(4-Methylpiperazin-1-yl) Methyl]benzoic Acid Dihydrochloride Hemihydrate

Abstract

The title compound, a salt of C13H20O2 2+ 2Cl− 0.5 H2O, (I), crystallizes in the monoclinic space group C 2/c with unit cell parameters a = 34.091(4) A, b = 7.2312(4) A, c = 12.5827(5) A, β = 96.870(6)°, Z = 8. The dihedral angle between the mean plane of the benzyl ring and the piperazin-1-yl group is 80.4(2)°, while the angle between the mean planes of the carbonyl group with that of the benzyl and piperazin-1-yl rings measure 6.6(3)° and 76.8(3)°, respectively. A short C=O and slightly extended C–O carboxyl bond in concert with weak intermolecular C–O···Cg π-ring interactions influences this twist angle with the benzyl ring and provides a slight interaction with the π conjugation of the benzene ring. Hydrogen bonding has no effect on the carboxylic group. Two separate two-center (acceptor bifurcated) Cl−···H–(N,O) hydrogen bonds are observed between one chloride anion and a water molecule and the piperazin-1-yl ring and a second chloride anion with a carboxyl oxygen atom and the piperazin-1-yl ring. These direct intermolecular couplings link the molecule into chains along the [010] plane of the unit cell which influence the twist angles of the benzyl and piperazin-1-yl rings and help stabilize crystal packing in the unit cell. Crystal Structure of 4-[(4-methylpiperazin-1-yl)methyl]benzoic acid dihydrochloride hemihydrate is reported and its geometric and packing parameters described and compared to a MOPAC computational calculation.