Vibrational spectra and structural studies of nonlinear optical crystal ammonium D, L-tartrate: a density functional theoretical approach

• Published in: Journal of Raman spectroscopy 2011-04, Vol.42 (4), p.676-684
• Main Authors: Vidya, S., Ravikumar, C., Hubert Joe, I., Kumaradhas, P., Devipriya, B., Raju, K.
• Format: Article
• Language: English
• Subjects: Activation; ammonium tartrate; charge transfer; Crystal structure; Density; density functional theory; Hydrogen bonding; NBO analysis; Nonlinearity; Single crystals; Stretching; vibrational spectra; Wavenumber
• ISSN: 0377-0486; 1097-4555; 1097-4555
• DOI: 10.1002/jrs.2743

Single crystals of ammonium D, L‐tartrate, a potential nonlinear optical (NLO) material of interest, were grown by the slow evaporation technique. The crystal structure was determined by single‐crystal X‐ray diffraction. Fourier transform infrared and Raman spectra of the crystallized molecule were recorded and analyzed. The geometry, intermolecular hydrogen bonding, first hyperpolarizability and harmonic vibrational wavenumbers were calculated with the help of B3LYP density functional theory method. The red shift of hydroxyl and NH4+ stretching wavenumbers indicate the formation of inter‐ and intramolecular hydrogen bonding. Simultaneous activation of CH stretching wavenumbers shows the presence of intramolecular charge transfer in the molecule. Natural bond orbital analysis was carried out to demonstrate the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule, leading to high NLO activity. Copyright © 2010 John Wiley & Sons, Ltd. FT‐Raman and IR spectra were used to investigate the ammonium tartrate crystal. The vibrational analysis explains the NLO activity and the charge transfer interactions of the molecule supported by density functional theory calculations. Natural bond orbital analysis clearly explains the various inter‐ and intramolecular interactions that are responsible for the stabilization of this molecule.