TY - INPR A1 - Wohlgemuth, Matthias A1 - Mitric, Roland T1 - Excitation energy transport in DNA modelled by multi-chromophoric field-induced surface hopping T2 - Physical Chemistry Chemical Physics N2 - Absorption of ultraviolet light is known as a major source of carcinogenic mutations of DNA. The underlying processes of excitation energy dissipation are yet not fully understood. In this work we provide a new and generally applicable route for studying the excitation energy transport in multi-chromophoric complexes at an atomistic level. The surface-hopping approach in the frame of the extended Frenkel exciton model combined with QM/MM techniques allowed us to simulate the photodynamics of the alternating (dAdT)10 : (dAdT)10 double-stranded DNA. In accordance with recent experiments, we find that the excited state decay is multiexponential, involving a long and a short component which are due to two distinct mechanisms: formation of long-lived delocalized excitonic and charge transfer states vs. ultrafast decaying localized states resembling those of the bare nucleobases. Our simulations explain all stages of the ultrafast photodynamics including initial photoexcitation, dynamical evolution out of the Franck-Condon region, excimer formation and nonradiative relaxation to the ground state. KW - Photodynamics KW - DNA Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-209467 ET - submitted version ER - TY - JOUR A1 - Wohlgemuth, Matthias A1 - Mitric, Roland T1 - Photochemical Chiral Symmetry Breaking in Alanine JF - Journal of Physical Chemistry A N2 - We introduce a general theoretical approach for the simulation of photochemical dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochemistry. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. We show that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochemistry of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7%, which is also in good correspondence to the experimental findings. Our method is generally applicable to complex systems and might serve to systematically explore the photochemical origin of homochirality. KW - circularly-polarized light KW - amino-acids KW - homochirality KW - molecular dynamics KW - dichroism Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-158557 UR - https://pubs.acs.org/doi/10.1021/acs.jpca.6b07611 N1 - This document is the Accepted Manuscript version of a Published Work that appeared in final form in Journal of Physical Chemistry A, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/10.1021/acs.jpca.6b07611 VL - 45 IS - 120 ER - TY - JOUR A1 - Turkin, Arthur A1 - Holzapfel, Marco A1 - Agarwal, Mohit A1 - Fischermeier, David A1 - Mitric, Roland A1 - Schweins, Ralf A1 - Gröhns, Franziska A1 - Lambert, Christoph T1 - Solvent Induced Helix Folding of Defined Indolenine Squaraine Oligomers JF - Chemistry—A European Journal N2 - A protecting group strategy was employed to synthesise a series of indolenine squaraine dye oligomers up to the nonamer. The longer oligomers show a distinct solvent dependence of the absorption spectra, that is, either a strong blue shift or a strong red shift of the lowest energy bands in the near infrared spectral region. This behaviour is explained by exciton coupling theory as being due to H- or J-type coupling of transition moments. The H-type coupling is a consequence of a helix folding in solvents with a small Hansen dispersity index. DOSY NMR, small angle neutron scattering (SANS), quantum chemical and force field calculations agree upon a helix structure with an unusually large pitch and open voids that are filled with solvent molecules, thereby forming a kind of clathrate. The thermodynamic parameters of the folding process were determined by temperature dependent optical absorption spectra. KW - UV/Vis spectroscopy KW - dye chemistry KW - solvent effects KW - superstructure KW - supramolecular folding Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-256869 VL - 27 IS - 32 ER - TY - INPR A1 - Titov, Evgenii A1 - Humeniuk, Alexander A1 - Mitric, Roland T1 - Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections T2 - Chemical Physics N2 - We assess the performance of two different types of basis sets for nonadiabatic quantum dynamics at conical intersections. The basis sets of both types are generated using Ehrenfest trajectories of nuclear coherent states. These trajectories can either serve as a moving (time-dependent) basis or be employed to sample a fixed (time-independent) basis. We demonstrate on the example of two-state two-dimensional and three-state five-dimensional models that both basis set types can yield highly accurate results for population transfer at intersections, as compared with reference quantum dynamics. The details of wave packet evolutions are discussed for the case of the two-dimensional model. The fixed basis is found to be superior to the moving one in reproducing nonlocal spreading and maintaining correct shape of the wave packet upon time evolution. Moreover, for the models considered, the fixed basis set outperforms the moving one in terms of computational efficiency. KW - Nonadiabatic quantum dynamics Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-199225 UR - https://doi.org/10.1016/j.chemphys.2019.110526 N1 - Submitted version ER - TY - INPR A1 - Titov, Evgenii A1 - Humeniuk, Alexander A1 - Mitric, Roland T1 - Exciton localization in excited-state dynamics of a tetracene trimer: A surface hopping LC-TDDFTB study T2 - Physical Chemistry Chemical Physics N2 - Excitons in the molecular aggregates of chromophores are key participants in important processes such as photosynthesis or the functioning of organic photovoltaic devices. Therefore, the exploration of exciton dynamics is crucial. Here we report on exciton localization during excited-state dynamics of the recently synthesized tetracene trimer [Liu et al., Org. Lett., 2017, 19, 580]. We employ the surface hopping approach to nonadiabatic molecular dynamics in conjunction with the long-range corrected time-dependent density functional tight binding (LC-TDDFTB) method [Humeniuk and Mitrić, Comput. Phys. Commun., 2017, 221, 174]. Utilizing a set of descriptors based on the transition density matrix, we perform comprehensive analysis of exciton dynamics. The obtained results reveal an ultrafast exciton localization to a single tetracene unit of the trimer during excited-state dynamics, along with exciton transfer between units. KW - Exciton dynamics Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198680 UR - https://doi.org/10.1039/C8CP05240A N1 - Accepted Manuscript ER - TY - INPR A1 - Titov, Evgenii A1 - Humeniuk, Alexander A1 - Mitric, Roland T1 - Comparison of moving and fixed basis sets for nonadiabatic quantum dynamics at conical intersections T2 - Chemical Physics N2 - We assess the performance of two different types of basis sets for nonadiabatic quantum dynamics at conical intersections. The basis sets of both types are generated using Ehrenfest trajectories of nuclear coherent states. These trajectories can either serve as a moving (time-dependent) basis or be employed to sample a fixed (time-independent) basis. We demonstrate on the example of two-state two-dimensional and three-state five-dimensional models that both basis set types can yield highly accurate results for population transfer at intersections, as compared with reference quantum dynamics. The details of wave packet evolutions are discussed for the case of the two-dimensional model. The fixed basis is found to be superior to the moving one in reproducing true nonlocal spreading and maintaining correct shape of the wave packet upon time evolution. Moreover, for the models considered, the fixed basis set outperforms the moving one in terms of computational efficiency. KW - Nonadiabatic quantum dynamics Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198699 UR - https://doi.org/10.1016/j.chemphys.2019.110526 N1 - Accepted manuscript ER - TY - JOUR A1 - Röhr, Merle I. S. A1 - Lisinetskaya, Polina G. A1 - Mitric, Roland T1 - Excitonic Properties of Ordered Metal Nanocluster Arrays: 2D Silver Clusters at Multiporphyrin Templates JF - Journal of Physical Chemistry A N2 - The design of ordered arrays of metal nanoclusters such as for example 2D cluster organic frameworks might open a new route towards the development of materials with tailored optical properties. Such systems could serve as plasmonically enhanced light-harvesting materials, sensors or catalysts. We present here a theoretical approach for the simulation of the optical properties of ordered arrays of metal clusters that is based on the ab initio parametrized Frenkel exciton model. We demonstrate that small atomically precise silver clusters can be assembled in one- and two-dimensional arrays on suitably designed porphyrin templates exhibiting remarkable optical properties. By employing explicit TDDFT calculations on smaller homologs, we show that the intrinsic optical properties of metal clusters are largely preserved but undergo J- and H-type excitonic coupling that results in controllable splitting of their excited states. Furthermore, ab initio parameterized Frenkel exciton model calculations allow us to predict an energetic splitting of up to 0.77 eV in extended two-dimensional square arrays and 0.79 eV in tilted square aggregates containing up to 25 cluster-porphyrin subunits. KW - Excitons KW - Porphyrin arrays Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159464 UR - https://pubs.acs.org/doi/10.1021/acs.jpca.6b04243 N1 - Accepted version VL - 120 IS - 26 ER - TY - INPR A1 - Röder, Anja A1 - Petersen, Jens A1 - Issler, Kevin A1 - Fischer, Ingo A1 - Mitric, Roland A1 - Poisson, Lionel T1 - Exploring the Excited-State Dynamics of Hydrocarbon Radicals, Biradicals and Carbenes using Time-Resolved Photoelectron Spectroscopy and Field-Induced Surface Hopping Simulations T2 - The Journal of Physical Chemistry A N2 - Reactive hydrocarbon molecules like radicals, biradicals and carbenes are not only key players in combustion processes and interstellar and atmospheric chemistry, but some of them are also important intermediates in organic synthesis. These systems typically possess many low-lying, strongly coupled electronic states. After light absorption, this leads to rich photodynamics characterized by a complex interplay of nuclear and electronic motion, which is still not comprehensively understood and not easy to investigate both experimentally and theoretically. In order to elucidate trends and contribute to a more general understanding, we here review our recent work on excited-state dynamics of open-shell hydrocarbon species using time-resolved photoelectron spectroscopy and field-induced surface hopping simulations, and report new results on the excited-state dynamics of the tropyl and the 1-methylallyl radical. The different dynamics are compared, and the difficulties and future directions of time-resolved photoelectron spectroscopy and excited state dynamics simulations of open-shell hydrocarbon molecules are discussed. KW - Excited state dynamics KW - Hydrocarbon radicals KW - time-resolved photoelectron spectroscopy KW - field-induced surface hopping Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198734 UR - https://doi.org/10.1021/acs.jpca.9b06346 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of Physical Chemistry A, copyright © American Chemical Society after peer review. To access the final edited and published work see Journal of Physical Chemistry A 2019, 123, 50, 10643-10662. https://doi.org/10.1021/acs.jpca.9b06346. ER - TY - INPR A1 - Röder, Anja A1 - Humeniuk, Alexander A1 - Giegerich, Jens A1 - Fischer, Ingo A1 - Poisson, Lionel A1 - Mitric, Roland T1 - Femtosecond Time-Resolved Photoelectron Spectroscopy of the Benzyl Radical T2 - Physical Chemistry Chemical Physics N2 - We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C\(_7\)H\(_7\) after UV excitation. Femtosecond time-resolved photoelectron imaging was applied to investigate the photodynamics of the radical. The experiments were accompanied by excited state dynamics simulations using surface hopping. Benzyl has been excited at 265 nm into the D-band (\(\pi\pi^*\)) and the dynamics was probed using probe wavelengths of 398 nm or 798 nm. With 398 nm probe a single time constant of around 70-80 fs was observed. When the dynamics was probed at 798 nm, a second time constant \(\tau_2\)=1.5 ps was visible. It is assigned to further non-radiative deactivation to the lower-lying D\(_1\)/D\(_2\) states. KW - Nonadiabatic dynamics KW - time-resolved photoelectron spectroscopy KW - benzyl radical Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159474 UR - http://dx.doi.org/10.1039/C7CP01437F N1 - Submitted version ER - TY - INPR A1 - Petersen, Jens A1 - Lindner, Joachim O. A1 - Mitric, Roland T1 - Ultrafast Photodynamics of Glucose T2 - Journal of Physical Chemistry B N2 - We have investigated the photodynamics of \(\beta\)-D-glucose employing our field-induced surface hopping method (FISH), which allows us to simulate the coupled electron-nuclear dynamics, including explicitly nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S\(_{1}\) and S\(_{2}\) states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs) whose geometries in most cases involve the elongation of a single O-H bond, while in some instances ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations explicitly including a UV laser pulse of 6.43 eV photon energy reveals that after initial excitation the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S\(_{1}\) state through the same types of CIs as observed in the field-free simulations. KW - photodynamics KW - nonadiabatic dynamics KW - conical intersections KW - carbohydrates Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159155 N1 - This document is the unedited Author’s version of a Submitted Work that was subsequently accepted for publication in Journal of Physical Chemistry, copyright © American Chemical Society after peer review. To access the final edited and published work see doi:10.1021/acs.jpcb.7b08602 ER -