strong hydrogen bond
Springer Online Journal Archives 1860-2000
Chemistry and Pharmacology
Abstract Side arm modifications of hexahomotriazacalixarene (1) were achieved by simple synthetic methods. Compound5 has picolyl side arms and liquid-liquid extraction experiments showed that the alkali cation affinity of5 is much stronger than that of1. A chiral group was also introduced into the azacalixarene structure. Calixarene was converted into dihomoazacalixarene (2) in 8% yield. Clathrate formation of2 with various solvents is described. MM3 calculations were carried out onp-substituted analogs of2. The ‘self-filled’ structure, in which the benzyl side arm is placed in its cavity, is the most stable structure when thep-positions of the aromatic rings carry small substituents. Strong hydrogen bonds between nitrogen and phenolic hydroxyl groups in dihomoazacalixarene (2) were observed at low temperatures. The1H-NMR signals of phenolic hydroxyl groups appeared as six singlets in the range of 9.8∼17.1 ppm at −70°C.
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