title: Evans hole and non linear optical activity in Bis(melaminium) sulphate dihydrate: A vibrational spectral study.
abstract: Bis(melaminium) sulphate dihydrate (BMSD), an interesting melaminium derivative for nonlinear optical activity, has been subjected to vibrational spectral analysis using FT IR and FT Raman spectra. The analysis has been aided by the Potential Energy Distribution (PED) of vibrational spectral bands, derived using density functional theory (DFT) at B3LYP/6-31G(d) level. The geometry is found to correlate well with the XRD structure and the band profiles for certain vibrations in the finger print region have been theoretically explained using Evans hole. The detailed Natural Bond Orbital (NBO) analysis of the hydrogen bonding in BMSD has also been carried out to understand the correlation between the stabilization energy of hyperconjugation of the lone pair of donor with the σ(∗) orbital of hydrogen-acceptor bond and the strength of hydrogen bond. The theoretical calculation shows that BMSD has NLO efficiency, 2.66 times that of urea. The frontier molecular orbital analysis points to a charge transfer, which contributes to NLO activity, through N-H…O intermolecular hydrogen bonding between the melaminium ring and the sulphate. The molecular electrostatic potential (MEP) mapping has also been performed for the detailed analysis of the mutual interactions between melaminium ring and sulphate ion.
authors.affiliation: Department of Physics, N M Christian College, Marthandam, Tamil Nadu, India.
authors.forename: V R
authors.initials: VR
authors.lastname: Suresh Kumar
authors.affiliation: Department of Physics, Government College, Nedumangad, Thiruvananthapuram, Kerala, India.
authors.forename: J
authors.initials: J
authors.lastname: Binoy
authors.affiliation: Department of Physics, N M Christian College, Marthandam, Tamil Nadu, India.
authors.forename: S
authors.initials: S
authors.lastname: Dawn Dharma Roy
authors.affiliation: Institute of Low Temperature and Structure Research, Polish Academy of Sciences, Okolna 2, 50-422 Wroclaw, Poland.
authors.forename: M K
authors.initials: MK
authors.lastname: Marchewka
authors.affiliation: Department of Physics, N M Christian College, Marthandam, Tamil Nadu, India. Electronic address: vsjkumar@gmail.com.
authors.forename: V S
authors.initials: VS
authors.lastname: Jayakumar
mesh_terms: D008958:Models, Molecular; D017711:Nonlinear Dynamics; D055620:Optical Phenomena; D011789:Quantum Theory; D017550:Spectroscopy, Fourier Transform Infrared; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics; D014227:Triazines / Q000737:chemistry*; D014732:Vibration; D014961:X-Ray Diffraction
chemical_list: D014227:Triazines; C000610488:bis(melaminium)sulphate dihydrate
keywords: DFT; Evans hole; FT-IR and FT-Raman spectra; HOMO–LUMO; MESP mapping; NLO