title: Vibrational spectroscopy of secondary amine salts: 1. Assignment of NH(2)(+) stretching frequencies in crystalline phases.
abstract: The NH(2)(+) stretching modes of secondary amine salts have been previously studied, but the band assignments are inconsistent between the various studies. This paper assigns characteristic NH(2)(+) group frequencies between approximately 2500 and 2400 cm(-1). Crystal structures of four diamine salts are reported here. Vibrational frequencies were calculated with the B3LYP hybrid Hartree-Fock/density functional method and the 6-31G(d) split-valence plus polarization basis set, and the results are in agreement with the experimental frequencies. Deuterium dilution experiments result in a group of sharply featured bands between the NH(2)(+) and the ND(2)(+) stretching bands. These bands, located between 2200 and 2100 cm(-1), are attributed to modes that contain contributions from coupled N-H and N-D stretching motions.
authors.affiliation: Department of Chemistry and Biochemistry, University of Oklahoma, 620 Parrington Oval, Rm 208, Norman, Oklahoma 73019, USA.
authors.forename: Guinevere A
authors.initials: GA
authors.lastname: Giffin
authors.forename: Scott
authors.initials: S
authors.lastname: Boesch
authors.forename: Dharshani N
authors.initials: DN
authors.lastname: Bopege
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Powell
authors.forename: Ralph A
authors.initials: RA
authors.lastname: Wheeler
authors.forename: Roger
authors.initials: R
authors.lastname: Frech
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D003959:Diamines / Q000737:chemistry*; D018054:Hydrobromic Acid / Q000737:chemistry; D006851:Hydrochloric Acid / Q000737:chemistry; D006860:Hydrogen Bonding; D012492:Salts / Q000737:chemistry*; D013057:Spectrum Analysis; D014732:Vibration
chemical_list: D003959:Diamines; D012492:Salts; D018054:Hydrobromic Acid; D006851:Hydrochloric Acid