title: P-Type Photochromism of New Helical Naphthopyrans: Synthesis and Photochemical, Photophysical and Theoretical Study.
abstract: Two novel helical naphthopyrans have been synthesised. The helical scaffold has the interesting effect of increasing the thermal stability of the transoid-trans (TT) open isomer formed upon UV irradiation of the closed form (CF), which transforms these naphthopyrans from thermal to photochemical photochromes. The photochromic performance is excellent in both polar and apolar solvents and the conversion percentage from the CF to the TT form can be as high as 92.8 %. We propose a new method to determine the quantum yields of the photochemical processes that lead to transoid-cis (TC) and TT isomers, and their molar absorption coefficients. The thermal stability of the TT and TC isomers has been studied in different solvents. The quantum yields of fluorescence before and after irradiation, along with the decay lifetimes, have also been measured. TD-DFT calculations have been performed to determine the relative thermodynamic stability of the species involved in the photochromic mechanism and to rationalise their spectral properties.
authors.affiliation: Institut Lavoisier de Versailles, UMR CNRS 8080, Université de Versailles Saint-Quentin-en-Yvelines, 45 av des Etats-Unis, 78035 Versailles (France). michel.frigoli@uvsq.fr.
authors.forename: Michel
authors.initials: M
authors.lastname: Frigoli
authors.affiliation: Institut Lavoisier de Versailles, UMR CNRS 8080, Université de Versailles Saint-Quentin-en-Yvelines, 45 av des Etats-Unis, 78035 Versailles (France).
authors.forename: Jérôme
authors.initials: J
authors.lastname: Marrot
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy).
authors.forename: Pier Luigi
authors.initials: PL
authors.lastname: Gentili
authors.affiliation: CEISAM, UMR CNRS 6230, Université de Nantes et Institut Universitaire de France, 2, rue de la Houssinière, 44322 Nantes (France). denis.jacquemin@univ-nantes.fr.|Institut Universitaire de France, 103, blvd Saint-Michel, 75005 Paris Cedex 05 (France). denis.jacquemin@univ-nantes.fr.
authors.forename: Denis
authors.initials: D
authors.lastname: Jacquemin
authors.affiliation: Associazione Laboratorio di Diagnostica per i Beni Culturali di Spoleto, Piazza Campello, 2 06049, Spoleto (PG) (Italy).
authors.forename: Manuela
authors.initials: M
authors.lastname: Vagnini
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy).
authors.forename: Danilo
authors.initials: D
authors.lastname: Pannacci
authors.affiliation: Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, Via Elce di Sotto 8, 06123 Perugia (Italy). fausto.ortica@unipg.it.|Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Perugia - Via Pascoli, 06123 Perugia (Italy). fausto.ortica@unipg.it.
authors.forename: Fausto
authors.initials: F
authors.lastname: Ortica
keywords: density functional calculations; helical structures; isomerization; naphthoyrans; photochromism