title: Reversible photochemical modifications in dicarbene-derived metallacycles with coumarin pendants.
abstract: Molecular rectangles were obtained from two bis(NHC) ligands, each featuring two terminal coumarin groups and two Ag(+), Au(+), or Cu(+) ions. Upon UV irradiation (λ=365 nm), the dinuclear complexes undergo photochemical modification through a [2+2] cycloaddition reaction of two adjacent coumarin moieties to give a macrocyclic tetra(NHC) ligand. The photodimerization of the coumarin pendants proceeds stereoselectively to give the syn-head-head isomers in all cases. Subsequent irradiation at λ=254 nm initiates a photocleavage reaction with reconstitution of the initial dinuclear complexes with coumarin pendants.
authors.affiliation: Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials, Department of Chemistry, Fudan University, 220 Handan Road, 200433 Shanghai (P.R. China); Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster, Corrensstraße 30, 48149 Münster (Germany). yfhan1980@fudan.edu.cn.
authors.forename: Ying-Feng
authors.initials: YF
authors.lastname: Han
authors.forename: Guo-Xin
authors.initials: GX
authors.lastname: Jin
authors.forename: Constantin G
authors.initials: CG
authors.lastname: Daniliuc
authors.forename: F Ekkehardt
authors.initials: FE
authors.lastname: Hahn
keywords: carbenes; coumarin; photochemical activation; photodimerization; supramolecular chemistry