Heterophane prototypes containing azolium and/or azole anion-binding motifs†
Revisiting a ‘3 + 1’ convergent stepwise strategy permitted the synthesis of imidazoliophane 2·2Br in excellent yield for a macrocyclization. The new triazoliophane 3 and bis(1,2,3-triazolium) counterpart 4·2Cl were less synthetically accessible and the hybrid derivative 5·Cl proved troublesome to prepare. Triazolophane 3 was devoid of anion-binding affinities, while charged heterophane prototypes showed a particular preference for acetate. When association constants were compared, dicationic systems 2·2PF6 and 4·2PF6 showed greater values than monocationic macrocycle 5·PF6, and the highest affinities corresponded to the bis(imidazolium) receptor 2·2PF6.