title: Cyclohexenylphenyldiazene: a simple surrogate of the azobenzene photochromic unit.
abstract: We have carried out an experimental and computational study on the ground- and excited-state photochemical and photophysical properties of (1-cyclohexenyl)phenyldiazene (CPD), a species formally derived from azobenzene in which one of the phenyl rings is replaced by a 1-cyclohexene substituent. The results show that CPD does substantially behave like azobenzene, but with a higher (approximately 70%) Phi(Z-->E) (npi*) photoisomerization quantum yield, calling for CPD as an effective alternative of azobenzene itself with new functionalization possibilities. By use of state-of-the-art ab initio CASPT2//CASSCF minimum energy path computations, we have identified the most efficient decay and isomerization routes of the absorbing singlet (pipi*), S1 (npi*), T1, and S0 states of CPD. The resulting mechanistic scheme agrees with experimental findings and provides a rationale of the observed photoisomerization quantum yields. Furthermore, this study provides a deep insight on the photophysical and photochemical properties of compounds based on the -N=N- double bond which supplies a general model for the photoreactivity of azobenzene-type compounds in general. This is expected to be a useful guideline for the design of novel photoreactive azo compounds.
authors.affiliation: Department of Chemistry G. Ciamician, University of Bologna, Via Selmi 2, 40126 Bologna, Italy.
authors.forename: Irene
authors.initials: I
authors.lastname: Conti
authors.forename: Filippo
authors.initials: F
authors.lastname: Marchioni
authors.forename: Alberto
authors.initials: A
authors.lastname: Credi
authors.forename: Giorgio
authors.initials: G
authors.lastname: Orlandi
authors.forename: Goffredo
authors.initials: G
authors.lastname: Rosini
authors.forename: Marco
authors.initials: M
authors.lastname: Garavelli