Known methods of synthesis of dihydropyrimidines and their oxidized products were modified, the impact of hydrogen bonds on stabilization of preferred tautomer and biological activities were studied.

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The synthesis and investigation of a new biologically active derivative of dihydropyrimidine are reported. The structure of the synthesized compound was investigated by X-ray single crystal diffraction method. In order to understand the molecular interactions, the Hirshfeld surface and contacts enrichment analyses were performed. The crystal packing is mainly stabilized by strong N-H…O hydrogen bonds and aromatic cycle stacking. Among the different types of oxygen atoms, the most electronegative had the highest propensity to form H-bonds. Biological activity of the synthesized compound was studied against E.coli, P. aeruginosa and S. aureus bacteria.

The nanostructuring of hydroxyl-substituted diazacrown-ether (DC) by silver nanoparticles was obtained by green synthesis method in order to increase the antibacterial activity of silver nanoparticles. The synthesized DC, nanoparticles, and nanosupramolecular complex (Ag@DC) were studied by TEM, powder-XRD, and NMR, IR, and UV spectroscopy methods. The Ag@DC nanostructures were uniform and their sizes ranged from 8 to 18 nm. IR and UV spectra revealed the noncovalent formation of the nanosupramolecular complex. The antibacterial activities of the prepared active agents were investigated on gram-positive and gram-negative bacteria by twofold microdilution method. Ultrastructural study by TEM was performed on E. coli BDU12 after treatment with Ag@DC. The results showed the improvement of the antibacterial action of Ag@DC compared to silver nanoparticles (E. coli BDU12-32 times, A. baumannii BDU32-16 times, K. pneumoniae BDU44 and P. aeruginosa BDU49-4 times, S. aureus BDU23-512 times). Chelating by DC significantly improved the antibacterial effects of the silver nanoparticles on gram-positive and gram-negative bacteria due to the ionophoric behavior of the crown ethers.