title: Experimental and DFT dimer modeling studies of the H-bond induced-vibration modes of l-β-Homoserine.
abstract: The vibrational spectra for l-β-Homoserine have been measured (IR absorption: 4000-400cm-1/Raman spectra: 4000-200cm-1). Characteristic vibrational modes of ammonium (-NH3+), carboxylate (-CO2-) and hydroxyl (-OH) groups across the 3700-1400cm-1are all identified to have originated in inter-molecular hydrogen bonding involving these functional groups. DFT calculations at B3LYP/6-311++G(d, p) level have yielded a single neutral monomer in the gas phase. Since as a member of the amino acids which are known to possess zwitterionic structure in condensed phase, the neutral monomer of l-β-Homoserine is optimized to a zwitterionic structure in a water medium. Consideration of two dimer structures, one dimer with -NH‧‧‧O bond and another -OH‧‧‧O bond, has given rise to vibrational modes that satisfactorily fit to all the observed absorption and Raman bands. It is found that the dimer with -OH‧‧‧O bond (binding energy, 8.896kcal/mol) is more tightly bound than the dimer with -NH‧‧‧O bond (8.363kcal/mol).
authors.affiliation: Vibrational Spectroscopy Group, Department of Physics, Karnatak University, Dharwad 580 003, Karnataka, India.
authors.forename: Shashikala
authors.initials: S
authors.lastname: Yalagi
authors.affiliation: Vibrational Spectroscopy Group, Department of Physics, Karnatak University, Dharwad 580 003, Karnataka, India.
authors.forename: J
authors.initials: J
authors.lastname: Tonannavar
authors.affiliation: Vibrational Spectroscopy Group, Department of Physics, Karnatak University, Dharwad 580 003, Karnataka, India. Electronic address: jyenagi.phys.kud@gmail.com.
authors.forename: Jayashree
authors.initials: J
authors.lastname: Yenagi
keywords: DFT; IR; NH‧‧‧O and OH‧‧‧O inter-molecular hydrogen bonding; Raman; Zwitterion; l-β-Homoserine