Photochromism of three supramolecular assemblies derived from benzenecarboxylate donors and viologen acceptors

Abstract

Based on 1,2,4,5-benzenetetracarboxylic acid (H4BTEC) and different viologen cations (MQ+ = 1-methyl-4,4′-bipyridinium cation; MV2+ = 1,1′-bis(methyl)-4,4′-bipyridinium dication; EV2+ = 1,1′-bis(ethyl)-4,4′-bipyridinium dication), three novel supramolecular assemblies [(H3O)(MQ)(H4BTEC)(H2BTEC)]·H2O (1), (H3O)(MV)0.5(BTEC)0.5 (2), (H3O)(EV)0.5(H2BTEC) (3), have been synthesized and structurally characterized with viologen cations as the guest and acid moieties acting as the host. The crystal structures and photochromic properties of three compounds have been explored. Similar to other viologen-based materials, compounds 2 and 3 are found to exhibit electron-transfer (ET) photochromism, while compound 1 has no photochromism observed. The photosensitivity of the compounds should be due to the rational modulation of electron acceptors and donors. Controllably fabricating appropriate donor and acceptor units at the molecular level in photosensitive materials is critical to the development of new photochromic host–guest materials.