H. Heitele

Bio: H. Heitele is an academic researcher from Technische Universität München. The author has contributed to research in topics: Electron transfer & Intramolecular force. The author has an hindex of 15, co-authored 18 publications receiving 986 citations.

Band-shape analysis of the charge-transfer fluorescence in barrelene-based electron donor-acceptor compounds

Abstract: In this paper we analyze the band shapes of the stationary fluorescence spectra for the radiative charge transfer recombination D + -A - →D-A+hv in a series of barrelene-based organic bridged donor (D)-acceptor (A) molecules D-A, exploring solvent polarity and temperature effects on the band shape. Free energy changes for charge recombination, medium reorganization energies, and intramolecular reorganization energies (for high- and medium-frequency vibrational modes) were evaluated from the band maximum energies and the full widths at half-maximum and from the fits of standard Franck-Condon factors to the entire fluorescence band shape

Solvent polarity effects on intramolecular electron transfer. 1. Energetic aspects

Abstract: Etude du transfert d'electron intramoleculaire de dimethylamino-4'' benzyl-4' benzyl-9- et benzyl-9 anthracenes

Energy Gap and Temperature Dependence of Photoinduced Electron Transfer in Porphyrin-Quinone Cyclophanes

Abstract: We have investigated intramolecular photoinduced charge separation and recombination in a series of cyclophane-bridged porphyrin-quinone systems by means of time-resolved fluorescence decay measurements. Rates of charge separation have been determined as a function of the free energy change of the reaction, of the polarity of the solvent, and of the temperature. In some systems a long-lived fluorescence is observed which is attributed to a thermal repopulation of the initially excited state from the charge transfer state. This delayed fluorescence allows the calculation of the rate of recombination in these cases. The observation of delayed fluorescence for a particular donor-acceptor compound in some solvent serves as a reference for the reaction free energy of the respective charge separation ([Delta]G[sub cs] [approx equal] 0 eV). The free energy change in other systems is estimated by correcting for differences in the redox potentials of the respective porphyrins and quinones. Electronic couplings and reorganization energies are determined by globally fitting standard rate expressions as a function of the free energy change to the experimental rate data. 32 refs., 5 figs., 4 tabs.

Structural Changes Accompanying Intramolecular Electron Transfer: Focus on Twisted Intramolecular Charge-Transfer States and Structures

Abstract: 6. Rehybridization of the Acceptor (RICT) 3908 7. Planarization of the Molecule (PICT) 3909 III. Fluorescence Spectroscopy 3909 A. Solvent Effects and the Model Compounds 3909 1. Solvent Effects on the Spectra 3909 2. Steric Effects and Model Compounds 3911 3. Bandwidths 3913 4. Isoemissive Points 3914 B. Dipole Moments 3915 C. Radiative Rates and Transition Moments 3916 1. Quantum Yields and Radiationless Deactivation Processes 3916

Contemporary Issues in Electron Transfer Research

Abstract: This is an overview of some of the important, challenging, and problematic issues in contemporary electron transfer research. After a qualitative discussion of electron transfer, its time and distance scales, energy curves, and basic parabolic energy models are introduced to define the electron transfer process. Application of transition state theory leads to the standard Marcus formulation of electron transfer rate constants. Electron transfer in solution is coupled to solvent polarization effects, and relaxation processes can contribute to and even control electron transfer. The inverted region, in which electron transfer rate constants decrease with increasing exoergicity, is one of the most striking phenomena in electron transfer chemistry. It is predicted by both semiclassical and quantum mechanical models, with the latter appropriate if there are coupled high- or medium-frequency vibrations. The intramolecular reorganizational energy has different contributions from different vibrational modes, whic...

Nucleobase-specific quenching of fluorescent dyes. 1. nucleobase one-electron redox potentials and their correlation with static and dynamic quenching efficiencies

Abstract: Intermolecular static and dynamic fluorescence quenching constants of eight coumarin derivatives by nucleobase derivatives have been determined in aqueous media. One common sequence of the quenching efficiency has been found for the nucleobases. The feasibility of a photoinduced electron transfer reaction for the nucleobase-specific quenching of fluorescent dyes is investigated by the calculation of the standard free energy changes with the Rehm−Weller equation. A complete set of one-electron redox potential data for the nucleobases are determined electrochemically in aprotic solvents for the first time, which are compared with values obtained by various other methods. Depending on the redox properties of the fluorescent dyes, the sequences of the quenching efficiencies can be rationalized by the orders of electrochemical oxidation potentials (vs NHE) of nucleosides (dG (+1.47 V) < dA < dC ≈ dT < U (≥ +2.39 V)) and reduction potentials (dG (< −2.76 V) < dA < dC < dT < U (−2.07 V)). The correlation between...