Cucurbit[8]uril-controlled [2 + 2] photodimerization of styrylpyridinium molecule

Abstract

Complexation of ( E )-4-(4-(1-methyl-pyridinium)styryl)-1-methyl-pyridinium chloride (SMP) guest and cucurbit[8]uril (CB[8]) host depending on the host-guest interactions which was characterized by 1 H NMR spectroscopy, electronic absorption, isothermal titration calorimetry, high-resolution electrospray mass spectrum and fluorescence spectroscopy. What’s more interesting is that the styryl units in supramolecular complexes can more easily undergo [2 + 2] photodimerization under the promotion of macrocyclic CB[8] when irradiated with visible light. • Complexation of SMP and CB[8] depending on the host-guest interaction. • The styryl group of SMP is located in the cavity of CB[8], resulting in a highly stable inclusion complex SMP@CB[8] with a host-guest binding ratio of 2:1. • The styryl units of supramolecular complexes can more easily undergo [2 + 2] photodimerization under the promotion of CB[8] when irradiated with visible light. he interaction of ( E )-4-(4-(1-methyl-pyridinium)styryl)-1-methyl-pyridinium chloride (SMP) guest, with cucurbit[8]uril (CB[8]) host was characterized by 1 H NMR spectroscopy, electronic absorption, isothermal titration calorimetry (ITC), high-resolution electrospray mass spectrum and fluorescence spectroscopy. Experimental data indicated that the styryl group of SMP resides within the cavity of CB[8] in aqueous solution, generating a highly stable inclusion complex SMP@CB[8] with a host-guest binding ratio of 1:2. Isothermal titration calorimetry experiments showed that the complexation of the SMP guest with CB[8] were enthalpy and entropy driven, which benefits from ion dipole interactions between the guest SMP and the host CB[8]. What’s more interesting is that the styryl units of supramolecular complexes can more easily undergo [2 + 2] photodimerization under the promotion of macrocyclic CB[8] when irradiated with visible light.