Two-photon isomerization properties of donor–acceptor Stenhouse adducts† † Electronic supplementary information (ESI) available: Detailed synthetic procedures and additional UV-Vis absorption spectra of molecules 1–6. 1H-NMR analysis of the open-closed populations. Determination of the photoconversion quantum yields. Spectra of the pure cyclopentenone form. Linear photochemistry results and calculations for the photoconversion quantum yields. Two-photon photochemistry of DASA 5 and 6. Time series of the spectra of 3, 4 and 6 under 800 nm excitation. Thermal evolution after two-photon conversion of 4 and 6. Calculations of the experimental two-photon absorption cross sections. Most relevant conformations for the computational studies. Isosurfaces of the molecular orbitals of 1, 3, 4. Comparison of experimental UV-Vis spectra with the TDDFT calculations. Vertical transition energies for each of the conformers. Two-photon absorption cross sections for each of the conformers. NMR spectra o

ABSTRACT: Donor–acceptor Stenhouse adducts (DASAs) are important photo-responsive molecules that undergo electrocyclic reactions after light absorption. From these properties, DASAs have received extensive attention as photo-switches with negative photochromism. Meanwhile, several photochemical applications require isomerization events to take place in highly localized volumes at variable depths. Such focused photoreactions can be achieved if the electronic excitation is induced through a non-linear optical process. In this contribution we describe DASAs substituted with extended donor groups which provide them with significant two-photon absorption properties. We characterized the photo-induced transformation of these DASAs from the open polymethinic form to their cyclopentenic isomer with the use of 800 nm femtosecond pulses. These studies verified that the biphotonic excitation produces equivalent photoreactions as linear absorbance. We also determined these DASAs' two-photon absorption cross sections from measurements of their photoconverted yield after biphotonic excitation. As we show, specific donor sections provide these systems with important biphotonic cross-sections as high as 615 GM units. Such properties make these DASAs among the most non-linearly active photo-switchable molecules. Calculations at the TDDFT level with the optimally tuned range-separated functional OT-CAM-B3LYP, together with quadratic response methods indicate that the non-linear photochemical properties in these molecules involve higher lying electronic states above the first excited singlet. This result is consistent with the observed relation between their two-photon chemistry and the onset of their short wavelength absorption features around 400 nm. This is the first report of the non-linear photochemistry of DASAs. The two-photon isomerization properties of DASAs extend their applications to 3D-photocontrol, non-linear lithography, variable depth birefringence, and localized drug delivery schemes. Photo-switching of Stenhouse donor–acceptor adducts by a non-linear optical input.

SUBMITTER: Reza-Gonzalez F 

PROVIDER: S-EPMC10231324 | biostudies-literature | 2023 Apr

REPOSITORIES: biostudies-literature