An ultrafast pre-organization of the [2+2] photocycloaddition of styryl dyes in 1:2 host-guest complexes with cucurbit[8]urils

• Published in: Chemical physics letters 2017-04, Vol.673, p.99-102
• Main Authors: Petrov, N.Kh, Ivanov, D.A., Shandarov, Yu.A., Kryukov, I.V., Svirida, A.D., Avakyan, V.G., Alfimov, M.V., Lobova, N.A., Gromov, S.P.
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2017.02.005

[Display omitted] •Ultrafast dynamic aspects of the [2+2] photocycloaddition of styryl dyes mediated by cucurbit[8]uril was studied by florescence upconversion technique.•The theoretical calculations indicate that the unexcited dyes inside the cavity does not fit the topochemical requirements.•Being in translational motion during its lifetime (about 4ps), an excited styryl dye inside host-guest complex gets the position that corresponds to the topochemical postulate. The photocycloaddition of styryl dyes 1, mediated by 1:2 hostguest complexes with cucurbit[8]urils (CB[8]), was studied by fluorescence upconversion techniques. The lifetime of 14.5ps for photoexcited 1 in aqueous solution and 3.8ps for that inside the complexes were gained from the fluorescence decay, the rate constant of quenching being obtained within the diffusion control limit. Calculations confirmed that unexcited pairs of 1 inside CB[8] does not fit the topochemical principles. So a translational movement is required to produce a reaction-ready structure that is in agreement with the timeresolved fluorescence anisotropy measured in the range of 5ps.