title: Synthesis, an experimental and quantum chemical computational study of a new nonlinear optical material: 2-picolinium hydrogensquarate.
abstract: The experimental and theoretical investigation results of a novel organic non-linear optical (NLO) organic squarate salt of 2-Picolinium hydrogensquarate (1), C6H8N+·C4HO4-, were reported in this study. The space group of the title compound was found in the monoclinic C2/c space group. It was found that the asymmetric unit consists of one monohydrogen squarate anion together with mono protonated 2-Picolinium, forming the (1) salt. The X-ray analysis clearly indicated that the crystal packing has shown the hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH⋯O interactions. The hydrogensquarate anions form α-dimer, while 2-Picolinium molecule interacts through NH⋯O and CH⋯O with the hydrogensquarate anion. The structural and vibrational properties of the compound were also studied by computational methods of ab initio performed on the compound at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) level of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 obtained are presented and compared with the X-ray analysis result. On the other the molecular electrostatic potential (MEP), electronic absorption spectra, frontier molecular orbitals (FMOs), conformational flexibility and non-linear optical properties (NLO) of the title compound were also studied at the 2 level and the results are reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.
authors.affiliation: Department of Physics, Faculty of Arts and Sciences, Ondokuzmayıs University, Kurupelit 55139, Samsun, Turkey. Electronic address: ukkorkmaz@gmail.com.
authors.forename: Ufuk
authors.initials: U
authors.lastname: Korkmaz
authors.affiliation: Department of Physics, Faculty of Arts and Sciences, Ondokuzmayıs University, Kurupelit 55139, Samsun, Turkey.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Bulut
mesh_terms: D000838:Anions; D003460:Crystallization; D003503:Cyclobutanes / Q000138:chemical synthesis / Q000737:chemistry*; D019281:Dimerization; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D055095:Optics and Photonics; D010847:Picolines / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D012984:Software; D013055:Spectrophotometry, Infrared; D013056:Spectrophotometry, Ultraviolet; D013696:Temperature; D014961:X-Ray Diffraction
chemical_list: D000838:Anions; D003503:Cyclobutanes; D010847:Picolines; D006859:Hydrogen; D009584:Nitrogen
keywords: Non-linear optical materials; Quantum chemical calculations; Squaric acid; Strong hydrogen bonding; Vibrational spectra; X-ray diffraction