Berlin 2014 – scientific programme
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MO: Fachverband Molekülphysik
MO 5: Posters 1: Electronic Spectroscopy, Photochemistry, Femtosecond Spectroscopy
MO 5.23: Poster
Monday, March 17, 2014, 16:30–18:30, Spree-Palais
Photoinduced Processes in a Low-Spin Cobalt(II) Semiquinonate Complex — •Fabian Rupp1, Katharina Chevalier1, Anneken Grün2, Manuel Zimmer2, Markus Gerhards2, Christoph van Wüllen2, Hans-Jörg Krüger2, and Rolf Diller1 — 1Dept. of Physics, Univ. of Kaiserslautern — 2Dept. of Chemistry, Univ. of Kaiserslautern, 67663 Kaiserslautern
Metal complexes undergoing valence tautomerism (VT) and spin-crossover (SCO) by external stimuli may be utilized as novel molecular switches. Femtosecond UV/Vis-pump- UV/Vis- and mid-IR-probe-spectroscopy is employed to investigate the first cobalt(II) semiquinonate complex [Co(L-N4tBu2)(dbsq)](B(p-C6H4Cl)4), that displays temperature dependent SCO rather than VT [1]. Surprisingly after photo-excitation in resonance with a CT-band at 1075 nm we do not observe the transient formation of a catecholate species (VT) but instead two intermediate excited semiquinonate states with different high-spin configuration (SCO) and lifetimes τ1 ≈ 0.9 ps and τ2 ≈ 9 ps, respectively, and a complete ground state recovery on a picosecond time scale. The assignment of the transient high-spin species in the photocycle is based on quantum chemical calculations, static electrochemical, temperature dependent UV/Vis, mid-IR, Raman and resonance-Raman spectroscopy.
[1] M. Graf et al., Angew. Chem. Int. Ed., 49, 950 (2010)