Premium
Photocontrolled Molecular Assembler Based on Cucurbit[8]uril: [2+2]‐Autophotocycloaddition of Styryl Dyes in the Solid State and in Water
Author(s) -
Gromov Sergey P.,
Vedernikov Artem I.,
Kuz'mina Lyudmila G.,
Kondratuk Dmitry V.,
Sazonov Sergey K.,
Strelenko Yuri A.,
Alfimov Michael V.,
Howard Judith A. K.
Publication year - 2010
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.200901324
Subject(s) - chemistry , cyclobutane , substituent , stereospecificity , aqueous solution , pyridine , cyclobutanes , crystallography , stereochemistry , stoichiometry , crystal structure , medicinal chemistry , organic chemistry , ring (chemistry) , catalysis
Three styryl dyes of the 4‐pyridine series that form syn ‐head‐to‐tail dimeric pairs in polycrystalline films were synthesised. NMR and UV/Vis spectroscopic studies showed that this promotes stereospecific [2+2]‐autophotocycloaddition (PCA) in the dimeric pairs to give rctt ‐isomers of cyclobutane derivatives. For the dye with an N ‐ammoniopropyl substituent, this transformation was accomplished according to the single‐crystal‐to‐single‐crystal pattern. In aqueous solutions, the dyes and cucurbit[ n ]urils (CB[ n ], n = 7, 8) form complexes with a pseudorotaxane structure. CB[7] tends to form 1:1 complexes, and CB[8] forms 1:1 and 2:1 complexes. The structure of the termolecular complex formed by the betaine of the N ‐sulfonatopropyl styryl dye and CB[8] was determined by X‐ray diffraction. The stability of the complexes was measured by 1 H NMR titration in a D 2 O/[D 3 ]MeCN (10:1) mixture (log K 1:1 ≥ 3.2, log K 2:1 ≥ 2.6). Free dyes and their complexes with CB[7] in water undergo only ( E )/( Z ) photoisomerisation. Termolecular complexes of all dyes with CB[8] were found to undergo effective stereospecific PCA reactions to give rctt isomers of cyclobutane derivatives. The 1:1 complexes of the obtained cyclobutanes with CB[8] (log K cb = 3.2–4.8) are less stable than those of the starting dyes with the same stoichiometry. Thus, CB[8] can play the role of a photocontrolled molecular assembler, i.e., even in the presence of 5 mol‐% of CB[8], complete conversion of styryl dyes into the corresponding cyclobutane derivatives takes place upon irradiation in solution.