Dresden 2011 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 34: Photochemistry

MO 34.1: Vortrag

Freitag, 18. März 2011, 10:30–10:45, TOE 317

Ring-closure and isomerization capabilities of spiropyran-derived merocyanine isomers — •Johannes Buback¹, Martin Kullmann¹, Patrick Nuernberger¹, Ralf Schmidt², Frank Würthner², and Tobias Brixner¹ — ¹Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg — ²Institut für Organische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

We report the photochemistry of two ring-open isomers, namely TTC and TTT, of a bidirectional photoswitchable spiropyran, 6,8-dinitro-1’,3’,3’-trimethylspiro[2H-1-benzopyran-2,2’-indoline] (6,8-dinitro BIPS). Both isomers are capable of ring closure after excitation with visible fs laser pulses, as disclosed by pump-wavelength-dependent transient absorption experiments in the visible spectral range. The main isomer TTC has its maximum absorption at 560 nm, whereas the minor isomer TTT is red shifted (600 nm). The excited-state lifetimes differ strongly (τ=902 ps for TTT and τ=94 ps for TTC), nevertheless the quantum efficiencies for ring closure (40% for TTC and 35% for TTT) and isomerization (1−2% for TTC and 1−2% for TTT) are comparable. With regard to the bidirectional photoswitching capabilities, 6,8-dinitro BIPS is the first molecular switch based on a 6π-electrocyclic reaction where both ring-open isomers are capable of ring closure.