title: Hydrogen-bonding between pyrimidine and water: a vibrational spectroscopic analysis.
abstract: We present an experimental and a theoretical study on hydrogen-bonding between pyrimidine and water as the H-donor. The degree of hydrogen-bonding in this binary system varies with mixture composition. This was monitored experimentally by polarization-resolved linear Raman spectroscopy with the pyrimidine ring breathing mode nu1 as a marker band. A subsequent quantitative line shape analysis of the isotropic Raman intensity for 24 pyrimidine/water mixtures clearly revealed a splitting into three spectral components upon dilution with water. The two additional peaks have been assigned to distinct groups of hydrogen-bonded species that differ in the number of pyrimidine nitrogen atoms (N) involved in hydrogen-bonding to water hydrogen atoms (H). From the integrated Raman intensities for "free" and "hydrogen-bonded" pyrimidine, a concentration profile for these species was established. Our assignments and interpretations are supported by quantum mechanical calculations of structures and by vibrational spectra for pyrimidine and 10 pyrimidine/water complexes with increasing water content. Also, accurate structure-spectra correlations for different cluster subgroups have been determined; within each particular cluster subgroup the water content varies, and a perfect negative correlation between NH hydrogen-bond distances and nu1 wavenumbers was observed.
authors.affiliation: Institut für Physikalische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg, Germany. sebastian.schluecker@uni-wuerzburg.de
authors.forename: S
authors.initials: S
authors.lastname: Schlücker
authors.forename: J
authors.initials: J
authors.lastname: Koster
authors.forename: R K
authors.initials: RK
authors.lastname: Singh
authors.forename: B P
authors.initials: BP
authors.lastname: Asthana
mesh_terms: D006860:Hydrogen Bonding; D046911:Macromolecular Substances / Q000737:chemistry; D011743:Pyrimidines / Q000737:chemistry*; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman; D014732:Vibration; D014867:Water / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D011743:Pyrimidines; D014867:Water; C030986:pyrimidine