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MO: Fachverband Molekülphysik
MO 9: Posters 1: Dichroism, VUV and Xray, Clusters, and Cold Molecules
MO 9.5: Poster
Dienstag, 7. März 2017, 17:00–19:00, P OG1
Transient absorption and VCD spectroscopy of two azobenzene derivatives with chiral sidegroups — •Kevin Artmann1, Karoline Buennemann2, Johannes Knorr1, Christian Merten2, and Patrick Nuernberger1 — 1Physikalische Chemie II, Ruhr-Universität Bochum, 44780 Bochum — 2Organische Chemie II, Ruhr-Universität Bochum, 44780 Bochum
Azobenzenes are a widely-studied class of photochromic molecular switches with versatile applicability. Their photoswitching is based on a trans/cis isomerization, with the exact isomerization mechanism still under debate and subject of many recent investigations [1]. We examine two azobenzene derivatives with chiral sidegroups: the one substituted in para position, whose cis isomer is observable for >48 h after photoswitching, shows ultrafast dynamics similar to unsubstituted azobenzene [2]. Global analysis yields three time constants for accurately describing the experimental data. The second azobenzene derivative, with two substituents in ortho position, behaves differently: the cis isomer is absent in stationary absorption spectra, yet transient absorption discloses that it is formed. Hence, a fast thermal back-isomerization occurs, caused by electronic and/or steric effects of the sidegroups. The experiments are complemented with IR and vibrational circular dichroism (VCD) studies: switching is observed in vibrational spectra for the para compound, whereas the fast back-reaction prevents the observation of VCD changes for the ortho compound.
*[1] H.M.D. Bandara, S.C. Burdette, Chem. Soc. Rev. 41, 1809 (2012).
*[2] I.K. Lednev et al., Chem. Phys. Lett. 290, 68 (1998).