title: Kinetic analysis of the thermal isomerisation pathways in an asymmetric double azobenzene switch.
abstract: Here we report a photochemical and kinetic study of the thermal relaxation reaction of a double azobenzene system, in which two azobenzene photochromic units are connected via a phenyl ring. Upon UV irradiation, three thermally unstable isomers are formed. Kinetic studies using arrayed (1)H-NMR spectroscopy revealed four distinct barriers for the thermal reversion to the stable isomer. The double isomerised Z,Z-2 can revert thermally to the E,E-2 isomer via either of two isomerisation pathways. The thermal Z to E isomerisations are not significantly affected by the state of the neighbouring azo-switching unit in the meta position. These findings are supported by quantum chemical calculations on the thermal Z to E isomerisation.
authors.affiliation: Stratingh Institute for Chemistry, Groningen, The Netherlands.
authors.forename: Jort
authors.initials: J
authors.lastname: Robertus
authors.forename: Siebren F
authors.initials: SF
authors.lastname: Reker
authors.forename: Thomas C
authors.initials: TC
authors.lastname: Pijper
authors.forename: Albert
authors.initials: A
authors.lastname: Deuzeman
authors.forename: Wesley R
authors.initials: WR
authors.lastname: Browne
authors.forename: Ben L
authors.initials: BL
authors.lastname: Feringa
mesh_terms: D001391:Azo Compounds / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D013237:Stereoisomerism; D013696:Temperature; D014466:Ultraviolet Rays
chemical_list: D001391:Azo Compounds; C009850:azobenzene