Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

MO: Fachverband Molekülphysik

MO 12: Photochemistry I

MO 12.2: Vortrag

Mittwoch, 10. März 2010, 11:00–11:15, F 142

Ultrafast bidirectional switching of a spiropyran system — •Martin Kullmann, Johannes Buback, Florian Langhojer, and Tobias Brixner — Institut für Physikalische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

Spiropyran, an example for a molecular switch, exists as a ring-open isomer (merocyanine) and as a ring-closed isomer (spiropyran) but only the ring-opening has been studied yet in detail. In this contribution we find ultrafast bidirectional switching for a dinitro substituted spiropyran (1’,3’-dihydro-1’,3’,3’-trimethyl-6,8-dinitrospiro[2H-1-benzopyran-2,2’-(2H)-indole] = 6,8-dinitro-BIPS).

We have carried out transient absorption experiments on 6,8-dinitro-BIPS in chloroform showing ultrafast photoreactions both for the ring-opening and the ring-closure direction. The ring-closure was observed with visible pump pulses (excitation to the S1 state of merocyanine) and probe pulses in the visible and the mid-infrared spectral range, indicating merocyanine bleach and spiropyran formation on a ps timescale. The ring opening reaction is also based on an ultrafast mechanism, as revealed by experiments using UV (266 nm) excitation and probing in the visible spectral range.

With the accumulated knowledge, two-color pump-repump-probe measurements were performed to induce ring-opening and the following reclosure showing a complete photocycle of the 6,8-dinitro-BIPS. This illustrates the possible application of spiropyrans as optical switches.