Synthesis and conformational structure of hydrazo-bridged homo calix[2]pyridine[2]triazines

Abstract

Presented in this paper are the practical synthesis and conformational structure of hydrazo-bridged homo calix[4]arenes. The step-wise fragment coupling method based on the nucleophilic aromatic substitution reaction of 2,6-dihydrazinylpyridine with 6-alkoxy-2,4-dichlorotriazine afforded effectively hydrazo-linked homo calix[2]pyridine[3]triazines. The exhaustive methylation of –NHNH– linkages led to lipophilic macrocycles, while the introduction of a THP-protected triglyme moiety on a triazine ring produced a water soluble hydrazo-bridged homo calix[2]pyridine[2]triazine. The acquired hydrazo-bridged homo calix[4]arenes adopted a cone conformational structure with two nitrogen atoms of the hydrazine linkage forming respectively a conjugation system with pyridine and triazine rings. The unique macrocyclic conformation and multidentate binding sites would render hydrazo-bridged homo calix[2]pyridine[2]triazines powerful hosts in molecular recognition and self-assembly.