Martin Klessinger

Bio: Martin Klessinger is an academic researcher from University of Münster. The author has contributed to research in topics: Excited state & Ab initio. The author has an hindex of 28, co-authored 117 publications receiving 2164 citations.

Calculation of the Vibronic Fine Structure in Electronic Spectra at Higher Temperatures. 1. Benzene and Pyrazine

Abstract: A program HOTFCHT for computing the vibronic fine structure of electronic spectra at different temperatures has been developed for a theoretical investigation of the temperature dependence of absor...

Theoretical model calculations of the proton affinities of aminoalkanes, aniline, and pyridine

Abstract: It is shown that the MP2(fc)/6-311+G**//HF/6-31G*+ZPE(HF/6-31G*) theoretical model reproduces very well the experimental proton affinities (PAs) of aminoalkanes and of some of their fluoro derivatives as well as the PAs of aniline and pyridine. In all molecules considered the nitrogen is most susceptible to proton attack. PA values of amino derivatives including aniline are shown to be linearly dependent on the nitrogen lone-pair s character. Increments I(X)α are derived for the amino group and the pyridine nitrogen, which extend the set of substituent increments derived previously for an additive estimation of PA values of polysubstituted benzenes.

Thermally Activated Delayed Fluorescence Materials Towards the Breakthrough of Organoelectronics

Abstract: The design and characterization of thermally activated delayed fluorescence (TADF) materials for optoelectronic applications represents an active area of recent research in organoelectronics. Noble metal-free TADF molecules offer unique optical and electronic properties arising from the efficient transition and interconversion between the lowest singlet (S1) and triplet (T1) excited states. Their ability to harvest triplet excitons for fluorescence through facilitated reverse intersystem crossing (T1→S1) could directly impact their properties and performances, which is attractive for a wide variety of low-cost optoelectronic devices. TADF-based organic light-emitting diodes, oxygen, and temperature sensors show significantly upgraded device performances that are comparable to the ones of traditional rare-metal complexes. Here we present an overview of the quick development in TADF mechanisms, materials, and applications. Fundamental principles on design strategies of TADF materials and the common relationship between the molecular structures and optoelectronic properties for diverse research topics and a survey of recent progress in the development of TADF materials, with a particular emphasis on their different types of metal-organic complexes, D-A molecules, and fullerenes, are highlighted. The success in the breakthrough of the theoretical and technical challenges that arise in developing high-performance TADF materials may pave the way to shape the future of organoelectronics.

Spin–orbit coupling and intersystem crossing in molecules

Abstract: Many light-induced molecular processes involve a change in spin state and are formally forbidden in non-relativistic quantum theory. To make them happen, spin–orbit coupling (SOC) has to be invoked. Intersystem crossing (ISC), the nonradiative transition between two electronic states of different multiplicity, plays a key role in photochemistry and photophysics with a broad range of applications including molecular photonics, biological photosensors, photodynamic therapy, and materials science. Quantum chemistry has become a valuable tool for gaining detailed insight into the mechanisms of ISC. After a short introduction highlighting the importance of ISC and a brief description of the relativistic origins of SOC, this article focusses on approximate SOC operators for practical use in molecular applications and reviews state-of-the-art theoretical methods for evaluating ISC rates. Finally, a few sample applications are discussed that underline the necessity of studying the mechanisms of ISC processes beyond qualitative rules such as the El-Sayed rules and the energy gap law. © 2011 John Wiley & Sons, Ltd.