Intramolecular N H···X (X=F, Cl, Br, and Ⅰ) hydrogen bonding patterns of aromatic amides in the solid state are summarized. It is revealed that the key for the formation of this kind of weak intramolec...Intramolecular N H···X (X=F, Cl, Br, and Ⅰ) hydrogen bonding patterns of aromatic amides in the solid state are summarized. It is revealed that the key for the formation of this kind of weak intramolecular hydrogen bonding in X-ray crystal structures is to suppress the competition of strong intermolecular N H···O C hydrogen bonding of the amide unit. For amides with identical backbones, the bonding capacity of halogen atoms as hydrogen bonding acceptors is in the order of F>Cl>Br>I, which is in accordance with their electronegativity strength. Generally, the five-membered hydrogen bonding is easier to form than the six-membered one.展开更多
Three arylamide-bridged biscoumarin derivatives 1-3 have been designed and prepared. Compounds 1 and 2 are induced by the intramolecular N?H…O and N·H…F hydrogen bonding to possess a helical conformation,and 3 ...Three arylamide-bridged biscoumarin derivatives 1-3 have been designed and prepared. Compounds 1 and 2 are induced by the intramolecular N?H…O and N·H…F hydrogen bonding to possess a helical conformation,and 3 is induced to have an extended conformation. A comparison of their absorption and fluorescent spectra in a variety of solvents of a wide range of polarity with those of control compound 4 reveals that,for foldamers 1 and 2,the intramolecular hydrogen bonding and the helical conformations exist in most solvents,but do not exist or are very weak in DMF and DMSO.展开更多
Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to la...Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to lack of one or two intramolecular hydrogen bonds at the middle aromatic unit. (2D) 1H NMR,circular dichroism and fluorescent studies revealed that both oligomers moderately complex n-octyl-α-L-glucopyranoside in chloroform.展开更多
基金the National Natural Science Foundation of China (21172042and 20974118)the Ministry of Education of China (IR1117) for financial support
文摘Intramolecular N H···X (X=F, Cl, Br, and Ⅰ) hydrogen bonding patterns of aromatic amides in the solid state are summarized. It is revealed that the key for the formation of this kind of weak intramolecular hydrogen bonding in X-ray crystal structures is to suppress the competition of strong intermolecular N H···O C hydrogen bonding of the amide unit. For amides with identical backbones, the bonding capacity of halogen atoms as hydrogen bonding acceptors is in the order of F>Cl>Br>I, which is in accordance with their electronegativity strength. Generally, the five-membered hydrogen bonding is easier to form than the six-membered one.
基金supported by the National Natural Science Foundation of China (20732007,20621062,20672137,20872167)the National Basic Research Program of China (2007CB808001)the Science and Technology Commission of Shanghai Municipality (09XD14-05300)
文摘Three arylamide-bridged biscoumarin derivatives 1-3 have been designed and prepared. Compounds 1 and 2 are induced by the intramolecular N?H…O and N·H…F hydrogen bonding to possess a helical conformation,and 3 is induced to have an extended conformation. A comparison of their absorption and fluorescent spectra in a variety of solvents of a wide range of polarity with those of control compound 4 reveals that,for foldamers 1 and 2,the intramolecular hydrogen bonding and the helical conformations exist in most solvents,but do not exist or are very weak in DMF and DMSO.
基金Supported by the National Natural Science Foundation of China(Grant Nos. 20732007, 20621062, 20872167, and 20672137)the National Basic Research Project (Grant No. 2007CB808000)the Chinese Academy of Sciences (Grant No. KJCX2-YW-H13)
文摘Two aromatic hydrazide haptamers have been prepared,with both consisting of two hydrogen bonded folded segments. Compared to their fully hydrogen bonded analogues,the flexibility of their backbones increases due to lack of one or two intramolecular hydrogen bonds at the middle aromatic unit. (2D) 1H NMR,circular dichroism and fluorescent studies revealed that both oligomers moderately complex n-octyl-α-L-glucopyranoside in chloroform.
