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MO: Fachverband Molekülphysik

MO 15: MO Poster 3

MO 15.2: Poster

Mittwoch, 11. März 2020, 17:00–19:00, Empore Lichthof

Monitoring the photochemistry of a formazan over 12 orders of magnitude in time — •Svenja Wortmann, Roger Jan Kutta, and Patrick Nuernberger — Institut für Physikalische und Theoretische Chemie, Universität Regensburg, 93040 Regensburg, Germany

Photoreaction of 2,3,5-triphenyltetrazolium chloride (TTC) in water yields 1,3,5-triphenyltetrazolium formazan (TPF) [1,2], used in TTC assays to indicate cellular respiration or cell growth [3]. From previous studies of formazan analogues only stationary spectra were reported. Exciting at 530 nm, the stable TPF conformer [4] performs an E-Z isomerization to a TPF-stereoisomer, observable by a hypsochromic shift [5]. At least 10 more isomers exist. So far, two conflicting mechanisms are suggested for the light-induced processes in TPF [6].

We studied the photochemistry of TPF in dependence on temperature, excitation wavelength, and solvent environment by time-resolved spectroscopy over 12 orders of magnitude in time. Additionally, vertical excitation energies for each potential TPF conformer were determined by time-dependent density functional theory for assignment of all observed intermediates. Thus, it is shown that the phototriggered dynamics have both ultrafast and very slow contributions with several isomers being accessed along the reaction path.

[1] T. Bolze et al., ChemPhysChem, 2018, 19, 138. [2] J. Hausser et al., Chem. Ber., 1949, 82, 195. [3] J. N. Eloff, Planta Medica, 1998, 64, 711. [4] F. Kanal et al., ChemPhysChem, 2015, 16, 3143. [5] L. S. Atabekyan et al., High Energy Chem, 2011, 45, 52. [6] C. Veas-Arancibia, Diss., Louisiana State University, 1986