75 74 Principal Scientist Profiles Benjamin Dietzek-IvanšiC Benjamin Dietzek-IvanšiC Principal Scientist Profiles BENJAMIN DIETZEK-IVANŠIC RESEARCH AREAS Prof. Dietzek-Ivanšić’s research in the field of molecular photonics focuses on understanding the relationship between structure, photoinduced dynamics and the function of molecules and molecular materials, including: • Electron transfer reactions in molecules in solution and in molecule-bulk interfaces • Photoinduced processes in drugs for photodynamic therapy and molecular sensors • Photoinduced processes in molecular sensors • Photophysics underlying molecular photocatalytic water-splitting • Developing experimental tools to characterize structural and electronic intermediates in (photo)catalytic cycles and the impact of local environment on the photophysics of molecules TEACHING FIELDS Benjamin Dietzek-Ivanšić is actively involved in the education of young developing researchers. His teaching includes classes in: • Physical Chemistry • Molecular Spectroscopy RESEARCH METHODS Prof. Dietzek-Ivanšić’s group uses a variety of spectroscopic methods to study the photoinduced function-determining processes in molecules and molecular materials: • Ultrafast time-resolved pump-probe spectroscopy spectroelectrochemistry • Time-resolved luminescence spectroscopy • Resonance-Raman spectroelectrochemistry • Ultrafast pump-probe microscopy • Vibrational sum-frequency generation • Time-resolved EPR spectroscopy PROFESSOR FOR PHYSICAL CHEMISTRY AT INSTITUTE OF PHYSICAL CHEMISTRY Benjamin Dietzek-Ivanšić, Fellow of the Royal Chemistry Society, is professor of Physical Chemistry, head of the research department Functional Interfaces and Deputy Scientific Director at the Leibniz Institute of Photonic Technology. He is a member of the executive board of the Abbe School of Photonics and member of the Board of Directors of the Jena Center for Soft Matter. He is co-spokesperson of the SFB/TRR 234 CATALIGHT and chair of the ITN LOGICLAB. His research was awarded with the Thüringer Forschungspreis für Angewandte Forschung in 2013 and the Prix Forcheurs Jean-Marie Lehn in 2018. RECENT RESEARCH RESULTS The group has recently been working on the photophysical mechanisms underlying structural changes in light-responsive polymer nanocarriers for target drug release. This work is performed in the context of the SFB 1278 POLYTARGET. Here we could demonstrate low-intensity upconversion in a noble-metal free polymer [1]. Furthermore, we investigated the photoacidity and photostability of a new class of naphtol-based polyermic photoacids [2, 3]. In collaboration with the Schacher group we investigated the impact of the local polymer environment on the light-activated reactivity of polymer-integrated photobases as a novel material to device light-responsive polymer nanostructures [4]. ECTRONIC INTERMEDIATES DURING SUPRAMOLECULAR PHOTOCATALYTIC WATER SPLITTING Recent research was devoted to studying the electronic intermediates in heterodinuclear transition-metal complexes, which serve as homogeneous photocatalysts for the production of molecular hydrogen as an environmentally clean fuel. The work performed in the context of the SFB/TRR 234 CATALIGHT combined ultrafast time-resolved optical pump-probe spectroscopy, with resonance Raman spectroscopy, electrochemistry and in-situ X-ray absorption near-edge structure spectroscopy to elucidate the impact of structural variations on the mechanism of charge transfer and of proton reduction. We identified a molecular vibrational mode efficiently coupling various excited electronic states and thereby facilitating electron transfer from the photoactive, i.e. light-absorption center of the molecule, to the catalytically active metal center. [Chem. Eur. J. 21, 7668 (2015)]. In-situ-XANES spectroscopy under catalytic conditions has aided the identification of the catalytically active species and has shown that the Pd-version of the molecular photocatalysts forms Pdcolloids under catalytic conditions, which the present the active species. However, exchange of the Pd-ion by Pt leads to a stable molecular photocatalyst [Angew. Chem. Int. Ed. 54, 5044, 2015] the catalytic efficiency of which can be tuned by exchanging the co-ligand structure at the Pt center [Angew. Chem. Int. Ed. 54, 6627, 2015]. Notably, the first ultrafast photoinduced electron transfer (two subsequent light-induced electron transfer processes are required to accumulate a sufficient number of redox equivalents on the catalytically active metal center for Hydrogen formation) are only minorly affected by the structural changes of the structural framework of the molecular catalyst. Introducing ultranfast time-resolved transient absorption spectroelectrochemistry to investigate molecular photocatalysts, we identified the excitation-wavelength specific excited state relaxation pathways, which lead to light-driven deactivation of a key intermediate of the catalytic cycle [Angew. Chem. Int. Ed. 58, 13140, 2019]. Further insight into the mechanism [Chem. Commun. 50, 5227, 2014] revealed a strong dispersion in the intermolecular charge transfer-characteristics upon electrochemical reduction of the molecular bridge connecting the photocenter of the complex with the catalytically active center. SERS Enhancement in the Spectra of Ruthenium Dye-Metal Nanoparticle Conjugates. Photoinduced dynamics of terpyridine 4H-imidazole-ruthenium complexes. [1] Sittig et al., Phys.Chem.Chem.Phys. 22, 4072 (2020). [2] Wendler et al., Macromol. Rapid Commun. 41, 1900607 (2020). [3] Wendler et al., Chem. Eur. J. 26, 2365 (2020). [4] Sittig et al., Chem. Eur. J. 27, 1072 (2020). Contact: Phone: + 49 3641-948360 Email: benjamin.dietzek@uni-jena.de ´
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