Mainz 2017 – wissenschaftliches Programm
MO 8.1: Hauptvortrag
Dienstag, 7. März 2017, 14:30–15:00, N 25
Ultrafast dynamics of a magnetically bistable molecular switch by fs transient absorption spectroscopy — •Sebastian Megow1, Julia Bahrenburg1, Hendrik Böhnke1, Mats Bohnsack1, Mark Dittner1, Marcel Dommaschk2, Rainer Herges2, and Friedrich Temps1 — 1Institute of Physical Chemistry, Christian-Albrechts-University, Max-Eyth-Strasse 1, 24098 Kiel, Germany — 2Otto-Diels-Institute of Organic Chemistry, Christian-Albrechts-University, Otto-Hahn-Platz 6/7, 24098 Kiel, Germany
The phenylazopyridine(PAP)-functionalized Ni-porphyrin-based molecular switch, dubbed "record player" (RP), has recently drawn considerable attention as it shows magnetic bistability at room temperature in homogeneous solution upon irradiation[Venkataramani et al., Science 331 (2011)]. The reversible photoswitching process between the diamagnetic low- and the paramagnetic high-spin compound occurs under isomerization and (de-)coordination of the PAP moiety. Suprisingly, the spin-crossover seems to be triggered by absoption in the porphyrin marcrocycle rather than photoisomerization of the PAP. To shed light on the underlying mechanism, we have monitored the ultrafast dynamics of the cis- and trans-PAP RP by means of fs transient absorption spectroscopy after photoexcitation. While the low-spin compound shows virtually identical dynamics to pure Ni-porphyrin without formation of any identifiable spin-switching product, the high-spin compound shows formation of the low-spin product within 12 ps with an estimated quantum yield of 6 ± 1 %.