title: The bis-barium complex of a butterfly crown ether as a phototunable supramolecular catalyst.
abstract: Reversible phototuning of the catalytic efficiency of the bis-barium complex of azobis(benzo-18-crown-6) in the basic ethanolysis of anilide derivatives has been achieved by light-induced cis right arrow over left arrow trans interconversion of the azobenzene spacer unit of the catalyst. The geometry of the productive catalyst-substrate complex is more favorable when the concave cis form of the catalyst is involved. Continuous photoregulation of the catalytic activity at any intermediate value between the "HIGH" and "LOW" levels was achieved by proper adjustment of the excitation wavelength or the irradiation time. The complete and relatively fast interconvertibility of photostationary states allowed the activity of the catalyst to be repeatedly photoswitched "HIGH" and "LOW" in the course of the same run.
authors.affiliation: Dipartimento di Chimica and ICCOM CNR-Sezione di Roma, Università La Sapienza, Box 34-ROMA 62, 00185 Roma, Italy. roberta.cacciapaglia@uniroma1.it
authors.forename: Roberta
authors.initials: R
authors.lastname: Cacciapaglia
authors.forename: Stefano
authors.initials: S
authors.lastname: Di Stefano
authors.forename: Luigi
authors.initials: L
authors.lastname: Mandolini