title: Structural aspects of intermolecular interactions in the solid state of 1,4-dibenzylpiperazines bearing nitrile or amidine groups.
abstract: The crystal structures of the title 1,4-bis(4-cyanobenzyl)piperazine (1) and 1,4-bis(4-amidinobenzyl)piperazine tetrahydrochloride tetrahydrate (2) are reported. Compound (1) crystallizes in the triclinic space group P\bar 1 and compound (2) in the monoclinic space group P21/n. In both (1) and (2) the asymmetric unit contains one half of the molecule because the central piperazine rings were located across a symmetry center. The packing of both molecules was dominated by hydrogen bonds. The crystal lattice of (1) was formed by weak C-H...N and C-H...π interactions. The crystal structure of (2) was completely different, with cations as well as chloride anions and water molecules taking part in intermolecular interactions. Single-crystal X-ray diffraction studies combined with density functional theory (DFT) calculations allowed the characterization of the intermolecular interactions in those two systems having different types of very strong electrophilic groups: non-ionic nitrile and ionic amidine. Chemical shift data from (13)C CP/MAS (Cross Polarization Magic Angle Spinning) NMR spectra were analyzed using the different procedures for the theoretical computation of shielding constants.
authors.affiliation: Department of Organic Chemistry, Faculty of Pharmacy, Medical University of Warsaw, Banacha 1, Warsaw 02 097, Poland.
authors.forename: Mateusz
authors.initials: M
authors.lastname: Rezler
authors.affiliation: Department of Organic Chemistry, Faculty of Pharmacy, Medical University of Warsaw, Banacha 1, Warsaw 02 097, Poland.
authors.forename: Teresa
authors.initials: T
authors.lastname: Żołek
authors.affiliation: Department of Crystallography, Faculty of Chemistry, Adam Mickiewicz University, Grunwaldzka 6, Poznań 60 780, Poland.
authors.forename: Irena
authors.initials: I
authors.lastname: Wolska
authors.affiliation: Department of Organic Chemistry, Faculty of Pharmacy, Medical University of Warsaw, Banacha 1, Warsaw 02 097, Poland.
authors.forename: Dorota
authors.initials: D
authors.lastname: Maciejewska
mesh_terms: D000578:Amidines / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry; D010879:Piperazines / Q000737:chemistry*; D014867:Water
chemical_list: D000578:Amidines; D009570:Nitriles; D010879:Piperazines; D014867:Water
keywords: density functional theory; pharmaceuticals; solid-state study; spanning X-ray diffraction