Spectroscopic and structural elucidation of 3,4-diaminopyridine and its hydrogentartarate salt: Crystal structure of 3,4-diaminopyridinium hydrogentartarate dihydrate

3,4-Diaminopyridinium hydrogen malonate

In the title salt, C₅H₈N₃⁺·C₃H₃O₄⁻, the 3,4-di­amino­pyridinium cation is almost planar, with an r.m.s. deviation of 0.02 Å. The conformation of the hydrogen malonate anion is stabilized by an intra­molecular O—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, N—H⋯O hydrogen bonds link cations and anions into layers parallel to the ab plane.

Anharmonic vibrational analysis of 3,4-diaminopyridine and 3-aminopyridine by density functional theory calculations

In this work, we will report a combined experimental and theoretical study on molecular structure and vibrational analysis of 3,4-diaminopyridine (3,4-DAP) and 3-aminopyridine (3-AP). The Fourier transform infrared and Fourier transform Raman spectra of 3,4-DAP were recorded in the solid phase. The molecular geometry, harmonic vibrational wavenumbers of 3-AP and 3,4-DAP in the ground-state have been calculated by using MP2 and density functional methods (B3LYP) using 6-311++G(d,p) as basis set. Predicted electronic absorption spectra 3,4-DAP from TD-DFT calculation have been analyzed comparing with the experimental UV-vis spectrum. The calculated HOMO and LUMO energies show that charge transfer occur in the molecule. A detailed interpretation of the infrared spectra of 3-AP and 3,4-DAP is reported. The theoretical spectrograms for FTIR and FT-Raman spectra of the title molecules have also been constructed. Comparison of the experimental spectra with anharmonic vibrational wavenumbers indicates that B3LYP results are more accurate.

Three-dimensional hydrogen-bonded structures in the 1:1 proton-transfer compounds of L-tartaric acid with the associative-group monosubstituted pyridines 3-aminopyridine, 3-carboxypyridine (nicotinic acid) and 2-carboxypyridine (picolinic acid)

The 1:1 proton-transfer compounds of L-tartaric acid with 3-aminopyridine [3-aminopyridinium hydrogen (2R,3R)-tartrate dihydrate, C(5)H(7)N(2)(+).C(4)H(5)O(6)(-).2H(2)O, (I)], pyridine-3-carboxylic acid (nicotinic acid) [anhydrous 3-carboxypyridinium hydrogen (2R,3R)-tartrate, C(6)H(6)NO(2)(+).C(4)H(5)O(6)(-), (II)] and pyridine-2-carboxylic acid [2-carboxypyridinium hydrogen (2R,3R)-tartrate monohydrate, C(6)H(6)NO(2)(+).C(4)H(5)O(6)(-).H(2)O, (III)] have been determined. In (I) and (II), there is a direct pyridinium-carboxyl N(+)-H...O hydrogen-bonding interaction, four-centred in (II), giving conjoint cyclic R(1)(2)(5) associations. In contrast, the N-H...O association in (III) is with a water O-atom acceptor, which provides links to separate tartrate anions through O(hydroxy) acceptors. All three compounds have the head-to-tail C(7) hydrogen-bonded chain substructures commonly associated with 1:1 proton-transfer hydrogen tartrate salts. These chains are extended into two-dimensional sheets which, in hydrates (I) and (III) additionally involve the solvent water molecules. Three-dimensional hydrogen-bonded structures are generated via crosslinking through the associative functional groups of the substituted pyridinium cations. In the sheet structure of (I), both water molecules act as donors and acceptors in interactions with separate carboxyl and hydroxy O-atom acceptors of the primary tartrate chains, closing conjoint cyclic R(4)(4)(8), R(3)(4)(11) and R(3)(3)(12) associations. Also, in (II) and (III) there are strong cation carboxyl-carboxyl O-H...O hydrogen bonds [O...O = 2.5387 (17) A in (II) and 2.441 (3) A in (III)], which in (II) form part of a cyclic R(2)(2)(6) inter-sheet association. This series of heteroaromatic Lewis base-hydrogen L-tartrate salts provides further examples of molecular assembly facilitated by the presence of the classical two-dimensional hydrogen-bonded hydrogen tartrate or hydrogen tartrate-water sheet substructures which are expanded into three-dimensional frameworks via peripheral cation bifunctional substituent-group crosslinking interactions.

Crystal structure and spectroscopic elucidation of 3-phenylpyridinium hydrogensquarate

The novel 3-phenylpyridinium hydrogensquarate (1) has been synthesized and its structure and properties are elucidated spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy, TGA, DSC, DTA and ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectrum. 3-Phenylpyridinium hydrogensquarate, crystallizes in the space group P-1 and the ions in the unit cell are joined into layers by intermolecular NH...O=C((Sq)) bonds with bond lengths of 2.625 and 2.626 A, respectively. Hydrogentartarates form dimers by strong O=COH...OCO interactions (2.499 A).

1,10-Phenanthrolinium hydrogensquarate monohydrate--a non-centrosymmetric structure from two non-chiral agents

The novel hydrogensquarate salt of 1,10-phenanthroline has been synthesized, isolated and structurally elucidated by single crystal X-ray diffraction. 1,10-Phenanthrolinium hydrogensquarate monohydrate (1) crystallizes in the non-centrosymmetric P2(1) space group. Its hydrogensquarate anions form a stable dimer by means of ((Sq))OHc...O=C((Sq)) hydrogen bonds with lengths of 2.509, 2.526, 2.510, and 2.524A. The solvent water molecule interacts with the anion dimers by means of strong and moderate hydrogen bonds HOHc...O=C((Sq)) with bond lengths of 2.782 and 2.845A, respectively. The 1,10-phenanthrolinium cation participates in NHc...OH(2) interactions with the water molecule (bond lengths of 2.810, 2.758, 2.779 and 2.760A). Surprisingly, compound contains four independent molecules in the unit cell. Optical properties were elucidated by means of linear-polarized solid-state IR-spectroscopy and UV-spectroscopy. In addition TGA, DSC, DTA data, positive and negative ESI mass spectra as well as (1)H- and (13)C NMR spectra are presented. Quantum chemical methods were used to calculate the electronic structure, vibrational data and electronic spectra as well as non-linear optical properties of neutral 1,10-phenanthroline and its protonated cation. Second harmonic generation measurements of the novel compound demonstrate that the compound possesses effective d coefficients of 1.9+/-0.5 pm V(-1), value that is about three times higher that of the low temperature form of potassium dideuterophosphate.

3,4-Diamino-pyridinium 4-nitro-benzoate-4-nitro-benzoic acid (1/1)

In the title compound, C₅H₈N₃⁺·C₇H₄NO₄⁻·C₇H₅NO₄, the non-H atoms of the 3,4-diamino­pyridinium cation are coplanar, with a maximum deviation of 0.022 (1) Å. The carboxyl­ate and nitro groups of the 4-nitro­benzoate anion are twisted out of the attached ring planes by dihedral angles of 15.89 (8) and 10.20 (8)°, respectively. In the 4-nitro­benzoic acid mol­ecule, the carboxyl and nitro groups form dihedral angles of 18.25 (8) and 6.55 (8)°, respectively, with the benzene ring. In the crystal, the constituent units form two-dimensional networks parallel to (001) by O—H⋯O, N—-H⋯O and C—H⋯O hydrogen bonds. Weak π–π inter­actions involving inversion-related 4-nitro­benzoic acid mol­ecules [centroid–centroid distance = 3.7325 (8) Å] and inversion-related 4-nitro­benzoate mol­ecules [centroid–centroid distance = 3.7124 (8) Å] are also observed.

3,4-Diamino-pyridinium hydrogen succinate

In the title compound, C₅H₈N₃⁺·C₄H₅O₄⁻, the pyridine N atom of the 3,4-diamino­pyridine mol­ecule is protonated. The protonated N atom participates in an N—H⋯O hydrogen bond to a succinate O atom of the singly deprotonated succinate anion. Each of the two amino groups are hydrogen-bonded to the O atoms of two different sets of succinate groups.. The crystal structure is further stabilized by O—H⋯O and C—H⋯O hydrogen bonds.

1,8-dinitro-4,5-dihydroxyantraquinone--solid-state linear-polarized IR-spectroscopy of oriented colloid particles as a suspension in nematic liquid crystal

By means of the linear-polarized IR-spectroscopic (IR-LD) tool to study the oriented solids samples as a colloid suspensions in nematic liquid crystal, the influence of the short contacts and pi-pi interactions in crystalline phase on IR-bands assignment and profile, i.e., relationship structure-spectroscopic properties, is studied in model system 1,8-dinitro-4,5-dihydroxyantraquinone. For a higher accuracy of the spectroscopic assignments a predetermination of the crystal structure in the same crystalline sample used in IR-LD spectroscopic elucidation is done. Some important aspects of pi-pi interactions and short contacts in solid phase are described. The advantages of the IR-LD method for an orientation of samples are demonstrated.