This work describes a rational approach for addressing the prototropy-related problems in heterocycle-based self-assembling systems by the use of degenerate prototropy. As a proof of principle, the utility of degenerate prototropy is demonstrated herein by developing heterocycle-based AADD-type self-assembling modules that exist as "single set of protameric pair (duplex)" in both solution and solid states. These self-assembling modules are quickly accessible in good yield by reacting 2-amino-5,5-disubstituted-1H-pyrimidine-4,6-diones, available in one step by the condensation of alpha,alpha-dialkyl malonates and free guanidine, with isocyanates. Evidence from NMR spectroscopy, ESI mass spectrometry, and single-crystal X-ray diffraction studies confirmed the formation of molecular duplexes. The effect of electronic repulsion in duplex formation is also investigated. Their ready synthetic accessibility, remarkably high propensity to crystal formation, and the novel property of degenerate prototropy would make these novel self-assembling molecules promising candidates for many proposed applications.

The variations in the endo- and exo-stereoselectivities for the reaction of cyclopentadiene (CP) with methyl acrylate (MA) have been investigated in salt−solvent reaction media (SSRM) at different concentrations of salts. The SSRM employed in the reaction include aqueous solutions of LiCl, NaCl, NaBr, CaCl2, guanidinium chloride, and LiClO4. The endo/exo (N/X) ratios have been noted to be sensitive to the ionic concentrations. Salts such as LiCl, NaCl, NaBr, and CaCl2 enhance the N/X ratios, while the solutions of guanidinium chloride and LiClO4 decrease them. The results have been analyzed in light of the salting-out and -in coefficients. The scaled particle theory has also been employed to calculate the contributions from the cavitation and solvation effects. The correlations of the N/X ratios with the surface tension of the SSRM are presented, which bring out clearly the impact of the surface tension of reaction media on the stereoselectivities of the above reaction. An attempt has also been made to interpret the results in terms of internal pressure of the SSRM in conjunction with the activation parameters. With the help of internal pressure, it is possible to suggest a division of zones to describe the salting-out and -in effects by different SSRM for the CP + MA reaction.

Barium hexaaluminate (BHA) synthesized by coupling of sol-gel process in reverse microemulsions shows a unique nanowhisker morphology and high surface area, which are retained after calcination at 1300 degrees C.

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Convenient chemical synthesis and incorporation of dithymidine and thymidine-cytidine dimer blocks connected with a five-atom amide linker N3'-CO-CH2-S-CH2 into oligonucleotides (ONs) are reported. The UV-Tm experiments for binding affinities of these mixed backbone ONs with complementary DNA and RNA sequences revealed important results such as significantly higher RNA-binding selectivity as compared with complementary DNA. NMR studies of the dimer blocks suggested a marginal increase in the N-type sugar conformations over that of the native DNA.