Very Short Intramolecular Hydrogen Bonds in the Crystal Structure of 1-[Bis(4-Fluorophenyl)Methyl]Piperazinediium Dimaleate

Abstract

The crystal structure of 1-[bis(4-fluorophenyl)methyl]piperazine-1,4-diium dimaleate has been determined at 130(1) K in order to analyze the short intramolecular hydrogen bonds in maleate anions. The salt crystallizes in the orthorhombic Pbca space group with unit-cell parameters: a = 9.7143(3) Å, b = 18.2668(3) Å, c = 27.2219(8) Å. The two anions display different kinds of very short intramolecular hydrogen bonds (O···O distance is 2.4184(12) and 2.4414(13) Å). In one of the anions the hydrogen atom is located asymmetrically, much closer to one of the oxygen atoms than to the other, while in the other anion the hydrogen atom is almost in the middle between two oxygen atoms. These positions were confirmed by the analysis of the difference Fourier maps. The dication is protonated on both nitrogen atoms of piperazine ring (which is in quite regular chair conformation), and all three N–H groups of the cation are involved in short and linear hydrogen bonds with oxygen atoms of the anions, not involved in intramolecular hydrogen bonds. These hydrogen bonds connect cations and anions into ribbons expanding along b-axis. Much weaker C–H···F, C–H···O and C–H···π interactions take part, along with the electrostatic and van der Waals interactions, in the determination of the crystal packing. The two anions display different kinds of very short intramolecular hydrogen bonds: in one of them the hydrogen atom is located asymmetrically, much closer to one of the oxygen atoms than to the other, while in the other anion the hydrogen atom is almost in the middle between two oxygen atoms.