title: Probing photochromic properties by correlation of UV-visible and infra-red absorption spectroscopy: a case study with cis-1,2-dicyano-1,2-bis(2,4,5-trimethyl-3-thienyl)ethene.
abstract: Quantification of the relative composition of the isomers in a photochromic system at any irradiation time interval is a critical issue in determining absolute quantum yields. For this purpose, we have developed a simple and convenient protocol involving combination of UV-visible and infra-red absorption spectroscopy. Photochromic cyclization reaction of cis-l,2-dicyano-l,2-bis(2,4,5-trimethyl-3-thieny1)ethene (CMTE) is analyzed to demonstrate the efficiency of the proposed methodology. This approach is based on the fact that the two isomers show distinctive infra-red bands. Detailed investigations of the UV-visible and infra-red spectra of the mixture obtained at different irradiation times in CCl(4) supported by quantum chemical computations lead to the unambiguous estimation of molar absorption coefficients of the closed isomer (epsilon(CF) = 4650 L mol(-1) cm(-1) at 512 nm). It facilitates the first determination of absolute quantum yields of this reversible photochromic reaction in CCl(4) by fitting the UV-visible spectral data (Phi(OF-->CF) = 0.41 +/- 0.05 and Phi(CF-->OF) = 0.12 +/- 0.02 at 405 nm and 546 nm, respectively).
authors.affiliation: PPSM, ENS Cachan, CNRS, UniverSud, 61 av President Wilson, 94230, Cachan, France.
authors.forename: Arnaud
authors.initials: A
authors.lastname: Spangenberg
authors.forename: Jose Alejandro
authors.initials: JA
authors.lastname: Piedras Perez
authors.forename: Abhijit
authors.initials: A
authors.lastname: Patra
authors.forename: Jonathan
authors.initials: J
authors.lastname: Piard
authors.forename: Arnaud
authors.initials: A
authors.lastname: Brosseau
authors.forename: Rémi
authors.initials: R
authors.lastname: Métivier
authors.forename: Keitaro
authors.initials: K
authors.lastname: Nakatani