Dr. Benjamin Koeppe

Profil

Zusammenfassung

Dr. Benjamin Koeppe erforscht Wasserstoffbrückenbindungen in molekularen Systemen durch kombinierte spektroskopische Methoden, insbesondere die Kopplung von NMR- und UV-Vis-Spektroskopie. Seine Expertise umfasst die Charakterisierung von Protonentransferprozessen, Wasserstoffbondgeometrien und die Entwicklung von Photoschaltern für die lichtgesteuerte Kontrolle chemischer Eigenschaften in wässrigen Lösungen.

Skills

Name

Dr. Benjamin Koeppe

Titel

Dr.

Fakultät

Mathematisch-Naturwissenschaftliche Fakultät

Institut

Institut für Chemie

Arbeitsgruppe

Organische Chemie und Funktionale Materialien

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HU-FIS-Profil

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28.6.2026, 01:08:15

• Entwicklung von molekularen Photoschaltern zur effektiven Steuerung des pH-Werts wässriger Lösungen durch sichtbares Licht

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  Förderer: DFG Eigene Stelle (Sachbeihilfe) Zeitraum: 08/2015 - 10/2018 Projektleitung: Dr. Benjamin Koeppe

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• Reaction Pathways of Proton Transfer in Hydrogen-Bonded Phenol–Carboxylate Complexes Explored by Combined UV–Vis and NMR Spectroscopy

  2011

  Journal of the American Chemical Society · 76 Zitationen · DOI

  Combined low-temperature NMR/UV-vis spectroscopy (UVNMR), where optical and NMR spectra are measured in the NMR spectrometer under the same conditions, has been set up and applied to the study of H-bonded anions A··H··X(-) (AH = 1-(13)C-2-chloro-4-nitrophenol, X(-) = 15 carboxylic acid anions, 5 phenolates, Cl(-), Br(-), I(-), and BF(4)(-)). In this series, H is shifted from A to X, modeling the proton-transfer pathway. The (1)H and (13)C chemical shifts and the H/D isotope effects on the latter provide information about averaged H-bond geometries. At the same time, red shifts of the π-π* UV-vis absorption bands are observed which correlate with the averaged H-bond geometries. However, on the UV-vis time scale, different tautomeric states and solvent configurations are in slow exchange. The combined data sets indicate that the proton transfer starts with a H-bond compression and a displacement of the proton toward the H-bond center, involving single-well configurations A-H···X(-). In the strong H-bond regime, coexisting tautomers A··H···X(-) and A(-)···H··X are observed by UV. Their geometries and statistical weights change continuously when the basicity of X(-) is increased. Finally, again a series of single-well structures of the type A(-)···H-X is observed. Interestingly, the UV-vis absorption bands are broadened inhomogeneously because of a distribution of H-bond geometries arising from different solvent configurations.

• Combined NMR and UV/Vis Spectroscopy in the Solution State: Study of the Geometries of Strong OHO Hydrogen Bonds of Phenols with Carboxylic Acids

  2009

  Angewandte Chemie International Edition · 58 Zitationen · DOI

  A head of the game: A new probe head for simultaneous NMR and UV/Vis spectroscopic measurements is designed. 1H NMR and UV/Vis spectra of an intermolecular hydrogen-bonded complex (see scheme) are measured simultaneously in CD2Cl2 at 175 K. Aided by the 1H NMR spectra, the sample concentration can be adjusted so that the desired complex is the exclusive form of the phenol present. The UV/Vis spectra allow the approximate position of the bridging proton to be found.

• N–H Stretching Excitations in Adenosine-Thymidine Base Pairs in Solution: Pair Geometries, Infrared Line Shapes, and Ultrafast Vibrational Dynamics

  2012

  The Journal of Physical Chemistry A · 54 Zitationen · DOI

  We explore the N-H stretching vibrations of adenosine-thymidine base pairs in chloroform solution with linear and nonlinear infrared spectroscopy. Based on estimates from NMR measurements and ab initio calculations, we conclude that adenosine and thymidine form hydrogen bonded base pairs in Watson-Crick, reverse Watson-Crick, Hoogsteen, and reverse Hoogsteen configurations with similar probability. Steady-state concentration and temperature dependent linear FT-IR studies, including H/D exchange experiments, reveal that these hydrogen-bonded base pairs have complex N-H/N-D stretching spectra with a multitude of spectral components. Nonlinear 2D-IR spectroscopic results, together with IR-pump-IR-probe measurements, as also corroborated by ab initio calculations, reveal that the number of N-H stretching transitions is larger than the total number of N-H stretching modes. This is explained by couplings to other modes, such as an underdamped low-frequency hydrogen-bond mode, and a Fermi resonance with NH(2) bending overtone levels of the adenosine amino-group. Our results demonstrate that modeling based on local N-H stretching vibrations only is not sufficient and call for further refinement of the description of the N-H stretching manifolds of nucleic acid base pairs of adenosine and thymidine, incorporating a multitude of couplings with fingerprint and low-frequency modes.

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