title: Electrochemically controlled formation/dissociation of phosphonate-cavitand/methylpyridinium complexes.
abstract: The phosphorus-bridged cavitand 1 self-assembles very efficiently in CH2Cl2 with either the monopyridinium guest 2+ or the bispyridinium guest 3(2+). In the first case a 1:1 complex is obtained, whereas in the second case both 1:1 and 2:1 host-guest complexes are observed. The association between 1 and either one of the guests causes the quenching of the cavitand fluorescence; in the case of the adduct between 1 and 3(2+), the fluorescence of the latter is also quenched. Cavitand complexation is found to affect the reduction potential values of the electroactive guests. Voltammetric and spectroelectrochemical measurements show that upon one-electron reduction both guests are released from the cavity of 1. Owing to the chemical reversibility of such redox processes, the supramolecular complexes can be re-assembled upon removal of the extra electron from the guest. Systems of this kind are promising for the construction of switchable nanoscale devices and self-assembling supramolecular materials, the structure and properties of which can be reversibly controlled by electrochemical stimuli.
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi 2, 40126 Bologna (Italy), Fax: (+39) 051-209-9456.
authors.forename: Benoît
authors.initials: B
authors.lastname: Gadenne
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi 2, 40126 Bologna (Italy), Fax: (+39) 051-209-9456.
authors.forename: Monica
authors.initials: M
authors.lastname: Semeraro
authors.affiliation: Dipartimento di Chimica Organica e Industriale and INSTM, UdR Parma, Università di Parma, Viale Usberti 17 A, 43100 Parma (Italy), Fax: (+39) 0521-905472.
authors.forename: Roger M
authors.initials: RM
authors.lastname: Yebeutchou
authors.affiliation: Dipartimento di Chimica Organica e Industriale and INSTM, UdR Parma, Università di Parma, Viale Usberti 17 A, 43100 Parma (Italy), Fax: (+39) 0521-905472.
authors.forename: Francesca
authors.initials: F
authors.lastname: Tancini
authors.affiliation: Dipartimento di Chimica Organica e Industriale and INSTM, UdR Parma, Università di Parma, Viale Usberti 17 A, 43100 Parma (Italy), Fax: (+39) 0521-905472.
authors.forename: Laura
authors.initials: L
authors.lastname: Pirondini
authors.affiliation: Dipartimento di Chimica Organica e Industriale and INSTM, UdR Parma, Università di Parma, Viale Usberti 17 A, 43100 Parma (Italy), Fax: (+39) 0521-905472.
authors.forename: Enrico
authors.initials: E
authors.lastname: Dalcanale
authors.affiliation: Dipartimento di Chimica "G. Ciamician", Università di Bologna, Via Selmi 2, 40126 Bologna (Italy), Fax: (+39) 051-209-9456.
authors.forename: Alberto
authors.initials: A
authors.lastname: Credi