ИСТИНА

Previously we described the synthesis of supramolecular donor–acceptor complexes of bis(18-crown-6)stilbene with bisammonium derivatives of heterocyclic compounds [1,2]. The complexes were shown to possess a high stability in solution due to the double macrocycle–ammonium ion interaction. They can be used as “off–on” fluorescent indicators for metal cations [2] and as convenient model systems to study ultrafast electron transfer reactions [3]. In order to evaluate the effect of the nature of the donor component on the properties of the supramolecular complexes, we synthesized bis(18-crown-6)azobenzene 1, a weaker electron donor in comparison with the analogous stilbene. The structure, thermodynamic stability and photochemical properties of complexes of azobenzene 1 with bisammonium compounds 2–4 were studied by different techniques including quantum-chemical modeling. It was found that the stability constants of complexes 1•(2–4) are lower (up to tenfold) in comparison with the corresponding complexes of bis(18-crown-6)stilbene. The quantum yield of E–Z photoisomerization of azobenzene 1 decreases by an order of magnitude upon complexation with viologen 2 (excitation in the region of the * absorption of 1). This fact is attributable to relatively fast excited-state electron transfer reaction between the complex components. The charge-transfer absorption band of complex 1•2 is unobservable because it lies between the more intense bands associated with the local p-p* and n-p* electronic transitions of 1. This work was supported by the Russian Science Foundation (project № 14-13-00076) and the Russian Academy of Sciences (Branch of Chemistry and Material Sciences). References [1] Ushakov, E.N.; Gromov, S.P.; Vedernikov, A.I.; Malysheva, E.V.; Botsmanova, A.A.; Alfimov, M.V.; Eliasson, B.; Edlund, U.G.; Whitesell, J.K.; Fox, M.A. J. Phys. Chem. A, 2002, 106, 2020. [2] Vedernikov, A.I.; Ushakov, E.N.; Efremova, A.A.; Kuz’mina, L.G.; Moiseeva, A.A.; Lobova, N.A.; Churakov, A.V.; Strelenko, Y.A.; Alfimov, M.V.; Howard, J.A.K.; Gromov, S.P. J. Org. Chem., 2011, 76, 6768. [3] Ushakov, E.N.; Nadtochenko, V.A.; Gromov, S.P.; Vedernikov, A.I.; Lobova, N.A.; Alfimov, M.V.; Gostev, F.E.; Petrukhin, A.N.; Sarkisov, O.M. Chem. Phys., 2004, 298, 251.