Halogen anion-directed helical host chain and the effect of halogen anions on the inclusion property

Abstract

In this paper, a series of halogen anion-directed complexes 0.5[CH3OH] · 0.5[H2O] ⊂ [L1H2]2+ · 2[Cl− ] (crystal 1), 0.5[H2O], {[L1H2]2+}0.5 · [Br− ] (crystal 2), [L2H2]2+ · 2[Br]− (crystal 3), [L1H2]2+ · 2[] (crystal 4) and 2[L2H2]2+ · 2[] (crystal 5) were synthesised (L1 = diamine N,N,N′,N′-tetrabenzyl-2-butylyne-1,4-diamine, L2 = N,N,N′,N′-tetra-(p-tertbutylbenzyl)-ethyl-enediamine), in which the halogen anions act as templates, via N–H…X (halogen) interactions, generating the helical structures. The choice of anion in this process was shown to be crucial for the successful assembly of the host chains and as well the inclusion property, meanwhile, the conformation of L1 and L2 may also exert an important influence on the formation of helical structures. X-ray structure studies have shown that the ability of the halides to template the formation of the helical host chains follows the order Cl− > Br− > I− .