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The use of tris(4-aminophenyl)amine (TAPA) as central to the synthesis of both polyimines and polyimides and covalent organic frameworks and inorganic cages, among others, has grown in the last few years. The resulting materials exhibit high performance in their area of application. In this contribution, the crystal structures of two TAPA derivatives, triethyl (nitrilotris(benzene-4,1-diyl))tricarbamate (1) and triethyl 2,2′,2″-((nitrilotris(benzene-4,1-diyl))tris(azanediyl))tris(2-oxoacetate) (2), are described. The molecular and supramolecular structures of both compounds were compared between them and with analogous compounds. The analyses of their vibrational and 13C-CPMAS NMR spectroscopies, as well as their thermal stability, were included and corelated with the crystal structure. Hirshfeld surface analysis on the crystal structures of both TAPA derivatives revealed the stabilization of the crystal network via the amide N—H∙∙∙O interactions of dispersive nature in the carbamate, whereas dispersive carbonyl–carbonyl interactions also played a competitive role in the supramolecular arrangement of the oxamate. Interaction energy DFT calculations performed at the B3LYP/6-31G(d,p) level allowed us to estimate the energy contributions and nature of several interactions in terms of the stability of both crystal lattices. [ABSTRACT FROM AUTHOR]

Oxalamic acid derivatives are model molecules used in crystal engineering and molecular recognition both in solution and in the solid state. Despite their growing importance, hardly any information on polymorphism, stability and interrelations of their solid forms can be found in the literature. In this work, the molecular and supramolecular structures of three cocrystal solvates of formula H2pOx·2S (S = DMSO, DMF, ⅓(MeOH·2W); W = H2O) and the dimethylammonium salt of N,N′-(1,4-phenylene)dioxalamic acid (H2pOx) are described. The nature and energetics of non-covalent interactions were explored through computational methods including the evaluation of the Hirshfeld surface, two-dimensional fingerprint plots, energy-framework diagrams and crystal lattice energies. The X-ray structural parameters were correlated with experimental solid state IR, 13C-CPMAS, thermal analysis and SEM to elucidate the unknown molecular and supramolecular structures of two hydromorphs and three desolvated polymorphs of H2pOx. The role of the crystallized solvents was demonstrated to fix the conformation of H2pOx through hydrogen bonding and n/π → π* interactions, favoring the sp–ap conformation to fit the shape of the solvent. The interconversion pathways between the ten solid phases of H2pOx were stablished, relying on the crystal size and temperature to yield a specific solvent-free polymorph. [ABSTRACT FROM AUTHOR]

Two new molecular structures, namely 1,3-bis(trimethylsilyl)-1 H-benzimidazole-2(3 H)-thione, C13H22N2SSi2, (2), and 1-trimethylsilyl-1 H-benzimidazole-2(3 H)-thione, C10H14N2SSi, (3), are reported. Both systems were derived from 1 H-benzimidazole-2(3 H)-thione. Noncovalent C-H...π interactions between the centroid of the benzmidazole system and the SiMe3 groups form helicoidal arrangements in (2). Dimerization of (3) results in the formation of R22(8) rings via N-H...S interactions, along with parallel π-π interactions between imidazole and benzene rings. [ABSTRACT FROM AUTHOR]

Intramolecular hydrogen bond (HB) formation was analyzed in the model compounds N-(2-benzoylphenyl)acetamide, N-(2-benzoylphenyl)oxalamate and N1,N2-bis(2-benzoylphenyl)oxalamide. The formation of three-center hydrogen bonds in oxalyl derivatives was demonstrated in the solid state by the X-ray diffraction analysis of the geometric parameters associated with the molecular structures. The solvent effect on the chemical shift of H6 [δH6(DMSO-d6)–δH6(CDCl3)] and Δδ(ΝΗ)/ΔT measurements, in DMSO-d6 as solvent, have been used to establish the energetics associated with intramolecular hydrogen bonding. Two center intramolecular HB is not allowed in N-(2-benzoylphenyl)acetamide either in the solid state or in DMSO-d6 solution because of the unfavorable steric effects of the o-benzoyl group. The estimated ΔH° and ΔS° values for the hydrogen bonding disruption by DMSO-d6 of 28.3(0.1) kJ·mol-1 and 69.1(0.4) J·mol-1·K-1 for oxalamide, are in agreement with intramolecular three-center hydrogen bonding in solution. In the solid, the benzoyl group contributes to develop 1-D and 2-D crystal networks, through C–H•••A (A = O, π) and dipolar C=O•••A (A = CO, π) interactions, in oxalyl derivatives. To the best of our knowledge, this is the first example where three-center hydrogen bond is claimed to overcome steric constraints. [ABSTRACT FROM AUTHOR]

The reactions of the benzimidazole nitrogen atoms and the exocyclic amino group of 2-aminobenzimidazole with CS2 in NaOH basic medium followed by methylation with methyl iodide was explored. With careful control of the stoichiometric quantities and addition sequences, this set of reactions allows the selective functionalization of the benzimidazole ring with N-dithiocarbamate, S-methyldithiocarbamate or dimethyldithiocarboimidate groups. The products were characterized by 1H-, 13C-NMR spectroscopy and three of them by X-ray diffraction analysis. The preferred isomers, tautomers and conformers were established. [ABSTRACT FROM AUTHOR]

A new organic salt of metformin, an antidiabetic drug, and N,N′-(1,4-phenylene)dioxalamic acid, was mechanochemically synthesized, purified by crystallization from solution and characterized by single X-ray crystallography. The structure revealed a salt-type crystal hydrate composed of one dicationic metformin unit, two monoanionic units of the acid and four water molecules, namely H2Mf(HpOXA)2∙4H2O. X-ray powder, IR, 13C-CPMAS, thermal and BET adsorption–desorption analyses were performed to elucidate the structure of the molecular and supramolecular structure of the anhydrous microcrystalline mesoporous solid H2Mf(HpOXA)2. The results suggest that their structures, conformation and hydrogen bonding schemes are very similar. To the best of our knowledge, the selective formation of the monoanion HpOXA−, as well as its structure in the solid, is herein reported for the first time. Regular O(δ−)∙∙∙C(δ), O(δ−)∙∙∙N+ and bifacial O(δ−)∙∙∙C(δ)∙∙∙O(δ−) of n→π * charge-assisted interactions are herein described in H2MfA organic salts which could be responsible of the interactions of metformin in biologic systems. The results support the participation of n→π * charge-assisted interactions independently, and not just as a short contact imposed by the geometric constraint due to the hydrogen bonding patterns. [ABSTRACT FROM AUTHOR]

The title compound, C16H19NO5, crystallizes as a centrosymmetric dimer through strong O-H···O hydrogen-bonding interactions between the hydroxyphenyl and morpholinocarbonyl groups. The morpholinocarbonyl group is almost perpendicular to the propenoate moiety. Electron delocalization in the N-C(=O) fragment leads to the formation of hydrogen-bonded S(5) ring motifs through C-H···O interactions. [ABSTRACT FROM AUTHOR]

Discusses the crystal structure of 2-Amino-1,3-benzothiazole—ethyl coumarin-3-carboxylate. Formation of yellow monoclinic crystals; Intermolecular three-centered hydrogen bonding interaction; Donor-acceptor nature of the compound.

The title compounds, C12H9ClO4, (I), and C12H9BrO4, (II), are isomorphous and crystallize in the monoclinic space group P21/ c. Both compounds present an anti conformation between the 3-carb­oxy and the lactone carbonyl groups. Both carbonyl groups are out of the plane defined by the remaining chromene atoms, by 8.37 (6) and 17.57 (6)° for (I), and by 9.07 (8) and 18.96 (18)° for (II), owing to their involvement in inter­molecular inter­actions. In both compounds, layers of centrosymmetric hydrogen-bonded dimers are developed in the [ 22] plane through C—H⋯O inter­actions, involving both carbonyl groups as acceptors. Two families of dimers stack through C=O⋯C=O, C=O⋯π and C— X⋯C=O ( X = Cl and Br) dipolar inter­actions, as well as a C—H⋯π inter­action, developing the three-dimensional structure along the c axis. [ABSTRACT FROM AUTHOR]

The title compound, C14H22N2O6, possesses C i symmetry and crystallizes with one half-mol­ecule in the aymmetric unit. The structure can be described as cyclo­hexyl­diamide singly bonded to two ethyl carboxyl­ate groups. The supramolecular structure is achieved through inter­molecular hard N—H⋯O hydrogen-bonding inter­actions involving only the amide group. The full hydrogen-bonding network is described by the C22(8)[ S(5) S(5) C(4)] motif that develops along the c-axis direction. [ABSTRACT FROM AUTHOR]