title: Reversible Light-Controlled Cargo Release in Hydrogen-Bonded Dimeric Capsules.
abstract: We describe the synthesis of three tetraureacalix[4]arenes having four appended terminal azobenzene groups. In CD2Cl2 solution and at millimolar concentration, the thermally equilibrated all-trans-tetraureas dimerize quantitatively, encapsulating one Me4P(+) cation. The light-induced isomerization of the all-trans encapsulation complexes produced a plethora of isomeric cis-enriched counterparts displaying a reduction in cavity size. cis-enriched dimers not suitable for the encapsulation of the cation or a solvent molecule are also produced, leading to partial release of the cargo (Me4P(+)) to the bulk solution. The substitution of the terminal phenyl in the azobenzene groups plays a key role in controlling the amount of released cargo in quantities up to 70%. The switching between the two states (all-trans and cis-enriched capsules) proceeds with no detectable photodegradation, even when it is repeated multiple times.
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology , Avgda. Països Catalans 16, 43007 Tarragona, Spain.
authors.forename: Frank A
authors.initials: FA
authors.lastname: Arroyave
authors.affiliation: Institute of Chemical Research of Catalonia (ICIQ), The Barcelona Institute of Science and Technology , Avgda. Països Catalans 16, 43007 Tarragona, Spain.|Catalan Institution for Research and Advanced Studies (ICREA) , Passeig Lluís Companys, 23, 08010 Barcelona, Spain.
authors.forename: Pablo
authors.initials: P
authors.lastname: Ballester