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The new vibrational and computational studies on bis(2-aminopiridinium) fumarate -- fumaric acid (1:1) complex have been made. The molecular geometry, vibrational frequencies and intensities of vibrational bands have been interpreted with the aid of structure optimization based on density functional theory (B3LYP) method with 6-311++G(d,p) basis set. The highly occupied-lowly unoccupied molecular orbital energies and chemical reactivity of the molecule have been calculated with time-dependent density functional theory approach. Stability energies of the molecule have been studied using natural bond orbital analysis. The predicted nonlinear optical properties of the title compound are much greater that those of urea. In addition, the molecular electrostatic potential surfaces and thermodynamic properties were calculated. [ABSTRACT FROM AUTHOR]

Highlights: [•] Crystal structure was solved with single crystal X-ray measurements. [•] Solid state vibrational spectra of anilinium trichloroacetate were interpreted. [•] DFT calculations were performed. [•] Second harmonic generation efficiency was measured. [•] Role of hydrogen bonds in NLO phenomenon is analysed. [•] Frontier molecular orbitals and NBO analysis were done. [Copyright &y& Elsevier]

The crystals of the new melaminium arsenate (MAS) [C 3 H 7 N 6 + ⋅H 2 AsO 4 − ] were obtained by the slow evaporation of an aqueous solution at room temperature. Single crystal X-ray diffraction analysis reveals that the crystal belongs to triclinic system with centro symmetric space group P−1. The crystals are built up from single protonated melaminium residues and single dissociated arsenate H 2 AsO 4 − anions. The protonated melaminium ring is almost planar. A combination of ionic and donor–acceptor hydrogen-bond interactions linking together the melaminium and arsenate residues forms a three-dimensional network. Vibrational spectroscopic analysis is reported on the basis of FT-IR and FT-Raman spectra recorded at room temperature. Hydrogen bonded network present in the crystal gives notable vibrational effect. DSC has also been performed for the crystal shows no phase transition in the studied temperature range (113–293 K). [ABSTRACT FROM AUTHOR]