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Abstract: This Letter reports the evidences for intramolecular six-membered N–H···O hydrogen bonding in N-benzyl benzamides and five-membered N–H···N hydrogen bonding in N-(pyridin-2-ylmethyl) benzamide. Intramolecular six-membered N–H···X (X=O or F) hydrogen bonding in 2-methoxyl- or 2-fluorobenzamides is used to lock the amide proton from forming strong intermolecular N–H···On bonding. As a result, for the first time the new intramolecular hydrogen bonding patterns are observed in the crystal structures of nine amides, whereas the whole molecules give rise to a new class of three-center hydrogen bonding motif. 1H NMR study in chloroform-d also supports that this weak intramolecular hydrogen bonding pattern exists in solution. [Copyright &y& Elsevier]

Abstract: The capacity of sulfur to form intramolecular five- or six-membered S⋯H–N hydrogen bonding in aromatic amides is assessed. The five-membered S⋯H–N hydrogen bonding is observed in crystal structures of five compounds, whereas the six-membered S⋯H–N hydrogen bonding is revealed in crystal structures of three compounds. The trityl group has been used to promote formation of the weak hydrogen bonding because it efficiently inhibits the competition of the intermolecular CH–N hydrogen bonding. (2D) 1H NMR experiments indicate that both patterns also exist in chloroform. [Copyright &y& Elsevier]

Four hydrogen bonded rigid aromatic hydrazide macrocycles, which bear different number of chiral and/or achiral oligo(ethylene glycol) chains, have been synthesized. 1 H NMR, fluorescence, UV–vis absorption, and circular dichroism experiments showed that the three macrocycles bearing chiral side chains gave rise to one-dimensional chiral column aggregates in aqueous solution. Remarkably, the chiral side chains at two different positions induced the helicity chirality in opposite directions. [ABSTRACT FROM AUTHOR]

Abstract: Two new hydrazide-based quadruple hydrogen-bonding motifs are described. Dipodals based on these two motifs are revealed to form supramolecular polymers, which can further aggregate to form vesicles and/or organogels in hydrocarbons. The quadruple hydrogen-bonding motifs are characterized by the X-ray diffraction and (2D) 1H NMR experiments, while the vesicles and organogels are evidenced by SEM, AFM, TEM, and fluorescent microscopy. [Copyright &y& Elsevier]

This paper describes the synthesis and characterization of the first series of hydrogen bonding-driven hydrazide foldamers and their recognition for alkyl saccharides in chloroform. Oligomers 1, 2-4, 5, 6, and 7, which contain one, two, four, six, or twelve repeated dibenzoyl hydrazide residues, respectively, have been prepared. The rigid and planar conformations of 1 and 2 or 4 have been established with X-ray analysis and 1H NMR spectroscopy, whereas the folding and helical conformations of 5-7 have been evidenced by the 1D and 2D 1H NMR and IR spectroscopy and molecular mechanics calculations. Molecular mechanics calculations also revealed that 5, 6, and 7 possess a rigid cavity with size of Ca. 10.6 to 11.1 Å, and half of the carbonyl groups in the folding conformations are orientated inwardly inside the cavity. 1H NMR and CD experiments revealed that 5-7 efficiently complex alkylated mono- and disaccharides 32- 35 in chloroform. The association constants (Kassoc) of the complexes have been determined with the 1H NMR and fluorescent titration methods. The energy-minimized conformation of 6.34 has been obtained with molecular mechanics calculation. The hydrazide-based folding structures described here represent novel examples of hydrogen bonding-driven foldamers that act as artificial receptors for selective molecular recognition. [ABSTRACT FROM AUTHOR]