New crystalline forms of hydrated and anhydrous N-acylhydrazones are reported. The studied crystal structures were determined by single-crystal X-ray diffraction at 90 or 100 K. Transferred aspherical atom model (TAAM) structure refinements were performed with the aid of the most recent version of the University at Buffalo Databank (UBDB). The resulting crystal structures were analyzed in terms of molecular conformations, intermolecular interaction energies, and crystal packing motifs. For this purpose, solid-state NMR studies and theoretical calculations were conducted supplementarily. It was found that all studied hydrazones adopt the E configuration around the azine N–N bond and imino NC function in the solid state, whereas the hydrazide N–N–CO moiety exhibits the E and Z arrangement in the N-acyl and N-aroyl derivatives, respectively. The constrained energy scans confirmed the E conformation of the hydrazide unit and the E arrangement of pyridine and hydrazone N atoms as the most stable ones. The association modes in the studied crystals are dominated by strong hydrogen bonds of the N–H···O or N–H···N-type involving the amide group as a proton donor. Consequently, as indicated by lattice energy calculations, a significant increase in the crystal cohesive energy per asymmetric unit is observed when water molecules are incorporated into the crystal structure, because this enables efficient saturation of the hydrogen bond acceptor and donor atoms. On the other hand, a substantial contribution of π···π stacking interactions to the overall stabilization of the crystal nets was also found. Thus, when more bulky phenyl substituents are introduced, the cohesive energy becomes more favorable.

This study presents the synthesis and spectral analysis of new derivatives of 1,2,4-triazole-3-thione and 1,3,4-thiadiazole. New compounds were prepared by cyclization reaction of acyl thiosemicarbazide derivatives in the presence of alkaline and acidic media. All synthesized compounds were screened for their in vitro antibacterial activity by using the agar dilution technique. Six of the compounds had potential activity against Gram-positive bacteria (minimal inhibitory concentration [MIC] = 15.63–500 μg/mL). Some compounds showed good activity especially against Bacillus subtilis ATCC 6633 (MIC = 15.63–250 μg/mL), Staphylococcus aureus ATCC 25923 (MIC = 31.25–250 μg/mL), and Micrococcus luteus ATCC 10240 (MIC = 125–250 μg/mL).Graphical abstract

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By the reaction of 4-methyl-4H-1,2,4-triazole-3-thiol with ethyl bromoacetate, ethyl [(4-methyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetate (1) was obtained. This compound was converted to [(4-methyl-4H-1,2,4-triazol-3-yl)sulfanyl]acetohydrazide (2). In the reaction of 2 with isothiocyanates, new thiosemicarbazides 3a-3g were obtained. The cyclization of 3a-3g in 2% aqueous solution of sodium hydroxide led to the formation of 4H-1,2,4-triazole-3(2H)-thione derivatives 4a-4g, whereas the cyclization in acid media led to the formation of 2-amino-1,3,4-thiadiazole derivatives 5a-5g. Molecular structure was confirmed by X-ray structure analysis of 3a, 4g, 5a and 5g. Compounds 4a, 4b and 4g were investigated pharmacologically to determine their effect on the central nervous system (CNS) in mice.

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The reaction of sodium hydroxide with 2-aminoterephthalic acid leads to the formation of a complex of the general formula: [Na 2 (atpt)(H 2 O) 5 ]ÁH 2 O, where atpt = [NH 2 C 6 H 3 (COO) 2 ] 2-. Sodium 2-aminoterephthalate was synthesized and characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, thermal analysis and coupled TG-FT-IR technique. Crystallographic study of the sodium complex reveals that the compound crystallizes in the triclinic system, the space group P-1 with a = 7.983(3) Å , b = 8.405(3) Å , c = 11.311(5) Å , a = 70.74(3)°, b = 76.57(3)°, c = 83.12(3)°and V = 696.1(5) Å 3. On heating in air atmosphere the compound in question loses all water molecules in two steps in the temperature range 30-205°C. The anhydrous form of the complex is stable up to 370°C and then decomposes to sodium carbonate.

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