title: The formation of peroxide degradation products of photochromic triphenylimidazolyl radical-dimers.
abstract: Following the recent report of Abe and co-workers (Phys. Chem. Chem. Phys., 2012, 14, 5855) of the isolation of a bridging peroxide of a naphthalene-tethered bisimidazolyl diradical, it is reported herein that this degradation pathway is a more general phenomenon for the chromic dimers of 2,4,5-triphenylimidazolyl radical (TPIR) materials, with non-tethered TPIRs forming similar oxygen adducts. The peroxides of two derivatives have been characterised by single crystal X-ray diffraction (SC-XRD) and it is identified that the 4-position of the imidazolyl ring is the site susceptible to reaction with oxygen. Furthermore, mass spectrometry has been used to show that for a range of five known, non-tethered derivatives, peroxide formation can be detected within 30 minutes when samples are irradiated under an oxygen atmosphere, thus presenting a significant challenge to the long term use of this class of material in colour-switching device applications.
authors.affiliation: Department of Chemistry, Durham University, South Road, Durham, DH1 3LE, UK.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Edkins
authors.forename: Michael R
authors.initials: MR
authors.lastname: Probert
authors.forename: Katharina
authors.initials: K
authors.lastname: Fucke
authors.forename: Craig M
authors.initials: CM
authors.lastname: Robertson
authors.forename: Judith A K
authors.initials: JA
authors.lastname: Howard
authors.forename: Andrew
authors.initials: A
authors.lastname: Beeby
mesh_terms: D019281:Dimerization; D005609:Free Radicals / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry*; D015394:Molecular Structure; D010545:Peroxides / Q000138:chemical synthesis* / Q000737:chemistry; D055668:Photochemical Processes
chemical_list: D005609:Free Radicals; D007093:Imidazoles; D010545:Peroxides