Supramolecular Assemblies of Melamine-2-Thiobarbiturate and Melamine-Barbiturate-2-Thiobarbiturate: Experimental and Theoretical Studies

Abstract

In this work, we considered the formation of supramolecular assemblies of melamine-thiobarbiturate and melamine-barbiturate-thiobarbiturate. It is known that thiobarbituric acid can form many tautomers, as well as different motifs due to the change of C2=O to C2=S hydrogen bonds. We formed the crystal. The resulting crystals were studied with scanning electron microscopy (SEM), optical fluorescence microscopy, single crystal and powder (PXRD) X-ray diffraction analyses, and solid state nuclear magnetic resonance (ss NMR). These systems were theoretically studied using density functional theory (DFT) and classical molecular dynamics (MD) simulations. Interestingly, just as in the case of melamine barbiturate, during the crystallization process, hydrogen from the C5 moiety of thiobarbituric acid migrates to the melamine molecule. In addition, the resulting melamine thiobarbiturate crystals exhibit fluorescence behavior in the red region (~565–605 nm), while the melamine barbiturate crystals are fluorescent in the green region (512–542 nm).

Thionation of poly(2-ethyl-2-oxazoline) and its effect on solubility and cloud point

“…[57][58][59][60] While to our knowledge this class of polythioamides has not been simulated before, the chosen force field has been successfully used in recent works for poly(2-alkyl-2-oxazoline)s of the same length, 61 as well as for thioamide containing small molecules. 62 Chains were solvated with TIP3P water 63 in a cubic box with a minimum border-tosolute distance of 1 nm. After initial steepest descent minimization, a short 100 ps-long equilibration in NVT was performed followed by 10 ns in NPT, using the Berendsen thermostat and barostat respectively (300 K at 1 bar).…”