Halogen,hydrogen and electrostatic interactions in 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium nitrate and 2‐amino‐5‐chloro‐1,3‐benzoxazol‐3‐ium perchlorate

In the title compounds, C₇H₆ClN₂O⁺·NO₃⁻ and C₇H₆ClN₂O⁺·ClO₄⁻, the ions are connected by N—H...O hydrogen bonds and halogen interactions. Additionally, in the first compound, co‐operative π–π stacking and halogen...π interactions are observed. The energies of the observed interactions range from a value typical for very weak interactions (1.80 kJ mol⁻¹) to one typical for mildly strong interactions (53.01 kJ mol⁻¹). The iminium cations exist in an equilibrium form intermediate between exo‐ and endocyclic. This study provides structural insights relevant to the biochemical activity of 2‐amino‐5‐chloro‐1,3‐benzoxazole compounds.     

The synthesis,crystal structure and thermal studies of a mixed-ligand 1,10-phenanthroline and hexamethylenetetramine complex of lanthanum nitrate. Insight into coordination sphere geometry changes of lanthanide(III) 1,10-phenanthroline complexes

The structure of tetraaqua-bis(nitrato-O,O′)-(1,10-phenanthroline-N,N′)-lanthanum(III) 1,3,5,7-tetraazatricyclo[3.3.1.1^3,7]decane nitrate dihydrate, [La(NO₃)₂ · phen · (H₂O)₄]⁺ · hmt · NO ₃ ⁻ · 2H₂O, is presented. The lanthanum ion exhibits tenfold coordination and the polyhedron can be described as tetradecahedron. The complex cations, nitrate ions, water and hexamethylenetetramine molecules are assembled via hydrogen bonds, H–π rings and π–π stacking interactions into 3D supramolecular network. The bond strength of coordination sphere was calculated by means of the bond-valence method. The influence of La:phen stoichiometry and additional ligand on the changes of lanthanum(III) coordination sphere geometry in ten-coordinated complexes with 1,10-phenanthroline was discussed. The infrared spectrum of structure optimised by means of quantum mechanical calculations was analysed and compared with measured one. The obtained compound was characterised by thermogravimetric analysis in conjunction with evolved gases in the air atmosphere.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate and 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate: a combined structural and theoretical study

The 2‐aminobenzothiazole sulfonation intermediate 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium monohydrogen sulfate, C₇H₇N₂S⁺·HSO₄⁻, (I), and the final product 2‐iminio‐2,3‐dihydro‐1,3‐benzothiazole‐6‐sulfonate, C₇H₆N₂O₃S₂, (II), both have the endocyclic N atom protonated; compound (I) exists as an ion pair and (II) forms a zwitterion. Intermolecular N—H...O and O—H...O hydrogen bonds are seen in both structures, with bonding energy (calculated on the basis of density functional theory) ranging from 1.06 to 14.15 kcal mol⁻¹. Hydrogen bonding in (I) and (II) creates DDDD and C(8)C(9)C(9) first‐level graph sets, respectively. Face‐to‐face stacking interactions are observed in both (I) and (II), but they are extremely weak.     

The coupled TG-MS investigations of lanthanide(III) nitrate complexes with hexamethylenetetramine

New transition metal compounds of the general formula Ln(NO₃)₃·2[N₄(CH₂)₆]·nH₂O, where Ln = La, Nd, Sm, Gd, Tb, Dy, Er, Lu, and n = 7-12, were obtained. The compounds and the gases evolved in the course of their thermal decomposition were characterised by thermogravimetric analysis. The measurements were carried out in air and argon environment in order to compare the intermediate products, final products and the mechanism of the thermal decomposition. The combined TG-MS system was used to identify the main volatile products of thermal decomposition and fragmentation processes of the obtained compounds. This revised version was published online in July 2006 with corrections to the Cover Date.     

2,3‐Dihydro‐1,3‐benzothiazol‐2‐iminium hydrogen oxydiacetate: a combined structural and theoretical study

In the title compound, C₇H₇N₂S⁺·C₄H₅O₅⁻, the ions are connected by N—H...O hydrogen bonds. The hydrogen oxydiacetate residues are linked together by O—H...O hydrogen bonds disordered about centres of inversion into hydrogen‐bonded ribbon layers crosslinked by weak C—H...O and stacking interactions. The cation exists mainly in the 2,3‐dihydro‐1,3‐benzothiazol‐2‐iminium form, with a small participation of the 2‐aminobenzothiazolium form, based on the structural data and quantum mechanical calculations. This study provides structural insights relevant to the biochemical activity of benzothiazole molecules.