Abstract
Functionalised dialkoxy‐substituted tetraoxacalix[2]arene[2]triazine macrocycles 6 have been readily synthesised by the fragment coupling approach using methyl 3,5‐dihydroxy‐4‐alkoxybenzoates and cyanuric chloride as the starting materials under very mild conditions. AlCl~3~‐mediated deallylation and debenzylation reactions afforded the lower‐rim dihydroxy‐substituted tetraoxacalix[2]arene[2]triazine derivatives 11 and 13 in good yields. Although dialkoxy‐substituted tetraoxacalix[2]arene[2]triazine macrocycles are fluxional in solution on the NMR spectroscopy timescale, they adopt a symmetric or slightly distorted 1,3‐alternate conformation with the bridging oxygen atoms conjugated with the triazine rings. The dihydroxylated tetraoxacalix[2]arene[2]triazine 13 b, which gives a mixture of monomer and dimer in solution according to a diffusion NMR spectroscopy study, adopts a 1,3‐alternate conformation and forms a cyclic tetrameric assembly in the solid state due to the formation of intermolecular hydrogen‐bonding networks. This dihydroxylated macrocyclic host molecule, a hydrogen‐bond donor macrocycle with a V‐shaped cleft, interacts with 2,2′‐bipyridine, 4,4′‐bipyridine and 1,10‐phenanthroline guests. Although in solution they form the corresponding 1:1 complexes with binding constants ranging from 37.7 to 213 M^−1^, 2:2 host–guest complexes were observed in the crystalline state. Hydrogen‐bonding interactions, along with other non‐covalent interactions, such as lone‐pair‐electron–π and CH⋅⋅⋅π interactions, were found to be the driving force for the formation of host–guest complexes.