title: H/D isotopic recognition and temperature effects in IR spectra of hydrogen-bonded cyclic dimers in crystals: 3-methylcinnamic acid and 4-phenylbutyric acid.
abstract: In the present work, the experimental and theoretical study of the nature of the inter-hydrogen bond interactions in two different carboxylic acids, 3-methylcinnamic acid (3MCA) and 4-phenylbutyric acid (4PBA), were reported. The polarized IR spectra of 3MCA and 4PBA crystals were recorded at the frequency ranges of the νO-H and νO-D bands. The spectral properties of 3MCA and 4PBA interpreted with the aid of the calculations based on the "strong-coupling" model. The differences in the spectral properties of the two different dimeric systems in the crystals provide a valuable information about the existence of a direct relationship between the crystal spectral properties in IR and the electronic structure of the molecular systems. In 3MCA crystals strong vibrational exciton interactions favor a "tail-to-head" (TH)-type Davydov coupling widespread via the π-electrons, whereas in 4PBA crystals a weak "through-space" (SS) exciton coupling is responsible for a "side-to-side"-type coupling. The relative contribution of each individual exciton coupling mechanism in IR spectra generation strongly depends on temperature and molecular electronic structure. The H/D isotopic recognition effect, depending on a non-random distribution of protons and deuterons in the crystal hydrogen bridges, was also analyzed.
authors.affiliation: Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice, Poland. Electronic address: barbara.hachula@us.edu.pl.
authors.forename: Barbara
authors.initials: B
authors.lastname: Hachuła
authors.affiliation: Institute of Environmental Engineering of the Polish Academy of Sciences, 34 Maria Curie-Skłodowska Street, 41-819 Zabrze, Poland.
authors.forename: Magdalena
authors.initials: M
authors.lastname: Jabłońska-Czapla
authors.affiliation: Institute of Chemistry, University of Silesia, 9 Szkolna Street, 40-006 Katowice, Poland.
authors.forename: Henryk T
authors.initials: HT
authors.lastname: Flakus
authors.affiliation: Institute of Physics, University of Silesia, 4 Uniwersytecka Street, 40-007 Katowice, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Nowak
authors.affiliation: Institute of Physics, University of Silesia, 4 Uniwersytecka Street, 40-007 Katowice, Poland.
authors.forename: Joachim
authors.initials: J
authors.lastname: Kusz
mesh_terms: D003460:Crystallization; D019281:Dimerization; D006860:Hydrogen Bonding; D008689:Methacrylates / Q000737:chemistry*; D010654:Phenylbutyrates / Q000737:chemistry*; D010666:Phenylpropionates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared
chemical_list: D008689:Methacrylates; D010654:Phenylbutyrates; D010666:Phenylpropionates; C510582:alpha-methylcinnamic acid; C075773:4-phenylbutyric acid
keywords: Dynamical co-operative interactions; H/D isotopic effects; Hydrogen bond; Polarized IR spectra; Temperature effects