Ethylenediammonium dication: H-bonded complexes with terephthalate, chloroacetate, phosphite, selenite and sulfamate anions. Detailed vibrational spectroscopic and theoretical studies of ethylenediammonium terephthalate

Vibrational spectra of the ortho-nitroanilinium cation in torsional space. Theoretical studies vs. experimental data of ortho-nitroanilinium chloride

Crystal structure of the ortho-nitroanilinium chloride, (HoNA)Cl, was re-determined by means of X-ray single crystal diffraction. Hydrogen atoms of the ammonio form intra- and intermolecular hydrogen bonds which are arranged in chain and ring patterns. The patterns are described by the mathematical relations of the elementary graph-set descriptors. Since the interactions have a weak nature, the interpretation of the vibrational spectra was carried out with the help of theoretical calculations of the spectra for the HoNA+ ion. In order to properly assign experimental bands, theoretical spectra were calculated at the B3LYP/6-31G(d,p) level of theory for the geometry of global minimum of HoNA+ ion as a reference and for the other conformations, including in-crystal geometry of the ion, changing the relative position of the ammonio and nitro groups. Overall, the 89 spectra were analyzed as a two-dimensional dependence of each of 45 normal modes of the HoNA+ ion on two dihedral angles, dih(HNCC) and dih(ONCC). Additionally, calculations were done for the in-crystal conformation of the (HoNA)Cl3(2-) anion. Great increase of frequency is observed for the ν7 (641 cm(-1)), where the H1C atom is involved in, because the intramolecular N-H1C⋯O hydrogen bond weakens upon rotation of the NH3+ group. PED analysis shows that also the modes of vibrations changes upon rotation. The mode of vibrations for the (HoNA)Cl3(2-) anion differs from the HoNA+ ion, especially for the ν(N-H) vibrations. Besides, when three chloride anions where included in the calculations, only then the experimental spectra were well reproduced.

FT-IR, FT-Raman spectra and DFT calculations of melaminium perchlorate monohydrate

Melaminium perchlorate monohydrate (MPM), an organic material has been synthesized by slow solvent evaporation method at room temperature. Powder X-ray diffraction analysis confirms that MPM crystal belongs to triclinic system with space group P-1. FTIR and FT Raman spectra are recorded at room temperature. Functional group assignment has been made for the melaminium cations and perchlorate anions. Vibrational spectra have also been discussed on the basis of quantum chemical density functional theory (DFT) calculations using Firefly (PC GAMESS) version 7.1 G. Vibrational frequencies are calculated and scaled values are compared with experimental values. The assignment of the bands has been made on the basis of the calculated PED. The Mulliken charges, HOMO-LUMO orbital energies are analyzed directly from Firefly program log files and graphically illustrated. HOMO-LUMO energy gap and other related molecular properties are also calculated. The theoretically constructed FT-IR and FT-Raman spectra of MPM coincide with the experimental one. The chemical structure of the compound has been established by (1)H and (13)C NMR spectra. No detectable signal was observed during powder test for second harmonic generation.