title: Self-assembly of hydrogensquarates: crystal structures and properties.
abstract: The self-assembly of the hydrogensquarates is elucidated by means of linear-polarized infrared (IR-LD) spectroscopy of oriented colloids in nematic host and the so-called reducing-difference procedure for polarized IR-LD spectra interpretation. The scopes and limitation are discussed on five novel derivatives of squaric acid and its anions, that is, 2-chloro-3-aminopyridinium hydrogensquarate (1), bis (1,2,3,4-tetrahydroquinolinium) squarate (2), bis hydrogensquarate dihydrate salt of 4-(aminomethyl)pyridine (3), N-(2-ammoniumethyl)-piperazinium monohydrate hydrogensquarate squarate (4), and 3-nitropyridinium hydrogensquarate monohydrate (5), respectively. The structures of these compounds 1-5 were solved by means of single-crystal X-ray diffraction, and the crystallographic data were used for the experimental elucidation of the corresponding IR spectra of crystals with respect to studying Fermi-resonance (FR), Davydov splitting (DS), and Fermi-Davydov (FD) as well as Evans' hole effects. The various motifs for self-assembly of squaric acid and its anions in the organic crystals are discussed together with their IR-spectroscopic properties.
authors.affiliation: Lehrstuhl für Analytische Chemie, Ruhr-Universität Bochum, 44780 Bochum, Germany. bkoleva@chem.uni-sofia.bg
authors.forename: B B
authors.initials: BB
authors.lastname: Koleva
authors.forename: T
authors.initials: T
authors.lastname: Kolev
authors.forename: R W
authors.initials: RW
authors.lastname: Seidel
authors.forename: M
authors.initials: M
authors.lastname: Spiteller
authors.forename: H
authors.initials: H
authors.lastname: Mayer-Figge
authors.forename: W S
authors.initials: WS
authors.lastname: Sheldrick
mesh_terms: D018360:Crystallography, X-Ray; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D013055:Spectrophotometry, Infrared
chemical_list: D006859:Hydrogen