TY - INPR A1 - Böhnke, Julian A1 - Dellermann, Theresa A1 - Celik, Mehmet Ali A1 - Krummenacher, Ivo A1 - Dewhurst, Rian D. A1 - Demeshko, Serhiy A1 - Ewing, William C. A1 - Hammond, Kai A1 - Heß, Merlin A1 - Bill, Eckhard A1 - Welz, Eileen A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Engels, Bernd A1 - Meyer, Franc A1 - Braunschweig, Holger T1 - Isolation of diradical products of twisted double bonds T2 - Nature Communications N2 - Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound. KW - diradicals KW - diborenes KW - carbenes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160248 N1 - Submitted version of Julian Böhnke, Theresa Dellermann, Mehmet Ali Celik, Ivo Krummenacher, Rian D. Dewhurst, Serhiy Demeshko, William C. Ewing, Kai Hammond, Merlin Heß, Eckhard Bill, Eileen Welz, Merle I. S. Röhr, Roland Mitrić, Bernd Engels, Franc Meyer & Holger Braunschweig: Isolation of diborenes and their 90°-twisted diradical congeners. Nature Communications. Volume 9, Article number: 1197 (2018) doi:10.1038/s41467-018-02998-3 ER - TY - JOUR A1 - Lisinetskaya, Polina A1 - Braun, Christian A1 - Proch, Sebastian A1 - Kim, Young Dok A1 - Ganteför, Gerd A1 - Mitrić, Roland T1 - Excited state nonadiabatic dynamics of bare and hydrated anionic gold clusters Au\(^−_3\)[H\(_2\)O]\(_n\) (n=0-2) JF - Physical Chemistry Chemical Physics N2 - We present a joint theoretical and experimental study of excited state dynamics in pure and hydrated anionic gold clusters Au\(^-_3\)[H\(_2\)O]\(_n\) (n = 0-2). We employ mixed quantum-classical dynamics combined with femtosecond time-resolved photoelectron spectroscopy in order to investigate the influence of hydration on excited state lifetimes and photo-dissociation dynamics. A gradual decrease of the excited state lifetime with the number of adsorbed water molecules as well as gold cluster fragmentation quenching by two or more water molecules are observed both in experiment and in simulations. Non-radiative relaxation and dissociation in excited states are found to be responsible for the excited state population depletion. Time constants of these two processes strongly depend on the number of water molecules leading to the possibility to modulate excited state dynamics and fragmentation of the anionic cluster by adsorption of water molecules. KW - nonadiabatic dynamics KW - metal cluster KW - time-resolved photoelectron spectroscopy Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159176 UR - https://doi.org/10.1039/C5CP04297F SN - 1463-9076 N1 - Accepted version VL - 18 IS - 9 ER - TY - JOUR A1 - Lisinetskaya, Polina A1 - Röhr, Merle I. S. A1 - Mitrić, Roland T1 - First-principles simulation of light propagation and exciton dynamics in metal cluster nanostructures JF - Applied Physics B N2 - We present a theoretical approach for the simulation of the electric field and exciton propagation in ordered arrays constructed of molecular-sized noble metal clusters bound to organic polymer templates. In order to describe the electronic coupling between individual constituents of the nanostructure we use the ab initio parameterized transition charge method which is more accurate than the usual dipole-dipole coupling. The electronic population dynamics in the nanostructure under an external laser pulse excitation is simulated by numerical integration of the time-dependent Schrodinger equation employing the fully coupled Hamiltonian. The solution of the TDSE gives rise to time-dependent partial point charges for each subunit of the nanostructure, and the spatio-temporal electric field distribution is evaluated by means of classical electrodynamics methods. The time-dependent partial charges are determined based on the stationary partial and transition charges obtained in the framework of the TDDFT. In order to treat large plasmonic nanostructures constructed of many constituents, the approximate self-consistent iterative approach presented in (Lisinetskaya and Mitric in Phys Rev B 89:035433, 2014) is modified to include the transition-charge-based interaction. The developed methods are used to study the optical response and exciton dynamics of Ag-3(+) and porphyrin-Ag-4 dimers. Subsequently, the spatio-temporal electric field distribution in a ring constructed of ten porphyrin-Ag-4 subunits under the action of circularly polarized laser pulse is simulated. The presented methodology provides a theoretical basis for the investigation of coupled light-exciton propagation in nanoarchitectures built from molecular size metal nanoclusters in which quantum confinement effects are important. KW - metal-cluster hybrid systems KW - exciton transfer KW - optical response KW - transition density KW - total electric field KW - electric field distribution KW - transition dipole moment KW - transition charge Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159193 UR - https://doi.org/10.1007/s00340-016-6436-6 SN - 0946-2171 N1 - This is a post-peer-review, pre-copyedit version of an article published in Apllied Physcis B. The final authenticated version is available online at: http://dx.doi.org/10.1007/s00340-016-6436-6 VL - 122 IS - 6 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 - 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 - TY - JOUR A1 - Hoche, Joscha A1 - Schmitt, Hans-Christian A1 - Humeniuk, Alexander A1 - Fischer, Ingo A1 - Mitrić, Roland A1 - Röhr, Merle I. S. T1 - The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer JF - Physical Chemistry Chemical Physics N2 - The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck–Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6–7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale. KW - exciton dynamics KW - pyrene dimer Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159514 UR - http://dx.doi.org/10.1039/C7CP03990E N1 - Accepted version VL - 19 IS - 36 ER - TY - INPR A1 - Lambert, Christoph A1 - Völker, Sebastian F. A1 - Koch, Federico A1 - Schmiedel, Alexander A1 - Holzapfel, Marco A1 - Humeniuk, Alexander A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Brixner, Tobias T1 - Energy Transfer Between Squaraine Polymer Sections: From helix to zig-zag and All the Way Back T2 - Journal of the American Chemical Society N2 - Joint experimental and theoretical study of the absorption spectra of squaraine polymers in solution provide evidence that two different conformations are present in solution: a helix and a zig-zag structure. This unique situation allows investigating ultrafast energy transfer processes between different structural segments within a single polymer chain in solution. The understanding of the underlying dynamics is of fundamental importance for the development of novel materials for light-harvesting and optoelectronic applications. We combine here femtosecond transient absorption spectroscopy with time-resolved 2D electronic spectroscopy showing that ultrafast energy transfer within the squaraine polymer chains proceeds from initially excited helix segments to zig-zag segments or vice versa, depending on the solvent as well as on the excitation wavenumber. These observations contrast other conjugated polymers such as MEH-PPV where much slower intrachain energy transfer was reported. The reason for the very fast energy transfer in squaraine polymers is most likely a close matching of the density of states between donor and acceptor polymer segments because of very small reorganization energy in these cyanine-like chromophores. KW - energy transfer dynamics KW - squaraine polymer Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159607 UR - http://dx.doi.org/10.1021/jacs.5b03644 N1 - This document is the unedited Author's version of a Submitted Work that war subsequently accepted for publication in Journal of the American Chemical Society, copyright American Chemical Society after peer review. To access the final edited and published work see doi:10.1021/jacs.5b03644. 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 - 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 - Wohlgemuth, Matthias A1 - Miyazaki, Mitsuhiko A1 - Tsukada, Kohei A1 - Weiler, Martin A1 - Dopfer, Otto A1 - Fujii, Masaaki A1 - Mitrić, Roland T1 - Deciphering environment effects in peptide bond solvation dynamics by experiment and theory T2 - Physical Chemistry Chemical Physics N2 - Most proteins work in aqueous solution and the interaction with water strongly affects their structure and function. However, experimentally the motion of a specific single water molecule is difficult to trace by conventional methods, because they average over the heterogeneous solvation structure of bulk water surrounding the protein. Here, we provide a detailed atomistic picture of the water rearrangement dynamics around the –CONH– peptide linkage in the two model systems formanilide and acetanilide, which simply differ by the presence of a methyl group at the peptide linkage. The combination of picosecond pump–probe time-resolved infrared spectroscopy and molecular dynamics simulations demonstrates that the solvation dynamics at the molecular level is strongly influenced by this small structural difference. The effective timescales for solvent migration triggered by ionization are mainly controlled by the efficiency of the kinetic energy redistribution rather than the shape of the potential energy surface. This approach provides a fundamental understanding of protein hydration and may help to design functional molecules in solution with tailored properties. KW - hydration dynamics KW - trans-formanilide KW - water migration KW - protein hydration KW - infrared-spectra Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-159483 UR - http://pubs.rsc.org/en/content/articlelanding/2017/cp/c7cp03992a N1 - Submitted version ER - TY - JOUR A1 - Meza-Chincha, Ana-Lucia A1 - Lindner, Joachim O. A1 - Schindler, Dorothee A1 - Schmidt, David A1 - Krause, Ana-Maria A1 - Röhr, Merle I. S. A1 - Mitrić, Roland A1 - Würthner, Frank T1 - Impact of substituents on molecular properties and catalytic activities of trinuclear Ru macrocycles in water oxidation N2 - Herein we report a broad series of new trinuclear supramolecular Ru(bda) macrocycles bearing different substituents at the axial or equatorial ligands which enabled investigation of substituent effects on the catalytic activities in chemical and photocatalytic water oxidation. Our detailed investigations revealed that the activities of these functionalized macrocycles in water oxidation are significantly affected by the position at which the substituents were introduced. Interestingly, this effect could not be explained based on the redox properties of the catalysts since these are not markedly influenced by the functionalization of the ligands. Instead, detailed investigations by X-ray crystal structure analysis and theoretical simulations showed that conformational changes imparted by the substituents are responsible for the variation of catalytic activities of the Ru macrocycles. For the first time, macrocyclic structure of this class of water oxidation catalysts is unequivocally confirmed and experimental indication for a hydrogen-bonded water network present in the cavity of the macrocycles is provided by crystal structure analysis. We ascribe the high catalytic efficiency of our Ru(bda) macrocycles to cooperative proton abstractions facilitated by such a network of preorganized water molecules in their cavity, which is reminiscent of catalytic activities of enzymes at active sites. KW - water oxidation KW - self-assembly KW - solar fuels KW - supramolecular materials KW - catalysis Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-204653 UR - https://doi.org/10.1039/D0SC01097A SN - 2041-6539 ER - TY - JOUR A1 - Hoche, Joscha A1 - Schulz, Alexander A1 - Dietrich, Lysanne Monika A1 - Humeniuk, Alexander A1 - Stolte, Matthias A1 - Schmidt, David A1 - Brixner, Tobias A1 - Würthner, Frank A1 - Mitric, Roland T1 - The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes JF - Chemical Science N2 - Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran (DCBT). We measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier. KW - solvent-dependent fluorescence yield Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-198707 UR - https://doi.org/10.1039/C9SC05012D VL - 10 ER - TY - JOUR A1 - Hoche, Joscha A1 - Flock, Marco A1 - Miao, Xincheng A1 - Philipp, Luca Nils A1 - Wenzel, Michael A1 - Fischer, Ingo A1 - Mitric, Roland T1 - Excimer formation dynamics in the isolated tetracene dimer JF - Chemical Science N2 - The understanding of excimer formation and its interplay with the singlet-correlated triplet pair state \(^{1}\)(TT) is of high significance for the development of efficient organic electronics. Here, we study the photoinduced dynamics of the tetracene dimer in the gas phase by time-resolved photoionisation and photoion imaging experiments as well as nonadiabatic dynamics simulations in order to obtain mechanistic insight into the excimer formation dynamics. The experiments are performed using a picosecond laser system for excitation into the S\(_{2}\) state and reveal a biexponential time dependence. The time constants, obtained as a function of excess energy, lie in the range between ≈10 ps and 100 ps and are assigned to the relaxation of the excimer on the S\(_{1}\) surface and to its deactivation to the ground state. Simulations of the quantum-classical photodynamics are carried out in the frame of the semi-empirical CISD and TD-lc-DFTB methods. Both theoretical approaches reveal a dominating relaxation pathway that is characterised by the formation of a perfectly stacked excimer. TD-lc-DFTB simulations have also uncovered a second relaxation channel into a less stable dimer conformation in the S\(_{1}\) state. Both methods have consistently shown that the electronic and geometric relaxation to the excimer state is completed in less than 10 ps. The inclusion of doubly excited states in the CISD dynamics and their diabatisation further allowed to observe a transient population of the \(^{1}\)(TT) state, which, however, gets depopulated on a timescale of 8 ps, leading finally to the trapping in the excimer minimum. KW - excimer formation KW - tetracene dimer KW - organic electronics Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-251559 VL - 12 IS - 36 SP - 11965 EP - 11975 ER - TY - JOUR A1 - Böhnke, Julian A1 - Dellermann, Theresa A1 - Celik, Mehmet Ali A1 - Krummenacher, Ivo A1 - Dewhurst, Rian D. A1 - Demeshko, Serhiy A1 - Ewing, William C. A1 - Hammond, Kai A1 - Heß, Merlin A1 - Bill, Eckhard A1 - Welz, Eileen A1 - Röhr, Merle I. S. A1 - Mitric, Roland A1 - Engels, Bernd A1 - Meyer, Franc A1 - Braunschweig, Holger T1 - Isolation of diborenes and their 90°-twisted diradical congeners JF - Nature Communications N2 - Molecules containing multiple bonds between atoms—most often in the form of olefins—are ubiquitous in nature, commerce, and science, and as such have a huge impact on everyday life. Given their prominence, over the last few decades, frequent attempts have been made to perturb the structure and reactivity of multiply-bound species through bending and twisting. However, only modest success has been achieved in the quest to completely twist double bonds in order to homolytically cleave the associated π bond. Here, we present the isolation of double-bond-containing species based on boron, as well as their fully twisted diradical congeners, by the incorporation of attached groups with different electronic properties. The compounds comprise a structurally authenticated set of diamagnetic multiply-bound and diradical singly-bound congeners of the same class of compound. KW - chemical bonding KW - diradicals KW - organometallic chemistry KW - diborenes KW - carbenes KW - boron Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-160431 VL - 9 IS - Article number: 1197 ER - TY - JOUR A1 - Muessig, Jonas H. A1 - Lisinetskaya, Polina A1 - Dewhurst, Rian D. A1 - Bertermann, Rüdiger A1 - Thaler, Melanie A1 - Mitric, Roland A1 - Braunschweig, Holger T1 - Dibortetraiodid (B\(_2\)I\(_4\)) ist im Festkörper ein Polymer aus sp3‐hybridisiertem Bor JF - Angewandte Chemie N2 - Anhand der ersten Festkörperstrukturen von Dibortetraiodid (B\(_2\)I\(_4\)) wird gezeigt, dass dieses nicht, wie lange angenommen, analog zu den leichteren Dibortetrahalogeniden B\(_2\)F\(_4\), B\(_2\)Cl\(_4\) und B\(_2\)Br\(_4\) in allen Aggregatzuständen in Form diskreter Moleküle mit planaren, dreifach koordinierten Boratomen vorliegt. Röntgenstrukturanalysen, Festkörper‐NMR‐ und IR‐Messungen zeigen, dass B\(_2\)I\(_4\) im Festkörper in zwei polymeren Konformeren vorkommt, die tetraedrisch koordinierte Boratome enthalten. Anhand von DFT‐Rechnungen werden die IR‐Spektren in Lösung und im Festkörper simuliert und mit den experimentellen Daten verglichen. KW - Bor KW - Diboran KW - DFT-Rechnungen KW - Festkörperstrukturen KW - Halogene Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-219653 VL - 132 IS - 14 ER - TY - JOUR A1 - Muessig, Jonas H. A1 - Lisinetskaya, Polina A1 - Dewhurst, Rian D. A1 - Bertermann, Rüdiger A1 - Thaler, Melanie A1 - Mitric, Roland A1 - Braunschweig, Holger T1 - Tetraiododiborane(4) (B\(_2\)I\(_4\)) is a Polymer based on sp\(^3\) Boron in the Solid State JF - Angewandte Chemie International Edition N2 - Herein we present the first solid‐state structures of tetraiododiborane(4) (B\(_2\)I\(_4\)), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\), and B\(_2\)Br\(_4\). Single‐crystal X‐ray diffraction, solid‐state NMR, and IR measurements indicate that B\(_2\)I\(_4\) in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid‐state structures, and these are compared with the experimental spectra. KW - boron tetraiodide KW - boron KW - density functional theory KW - diborane KW - halides KW - solid-state sturcture Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-209428 VL - 59 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 - 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 - JOUR A1 - Hirsch, Florian A1 - Pachner, Kai A1 - Fischer, Ingo A1 - Issler, Kevin A1 - Petersen, Jens A1 - Mitric, Roland A1 - Bakels, Sjors A1 - Rijs, Anouk M. T1 - Do Xylylenes Isomerize in Pyrolysis? JF - ChemPhysChem N2 - We report infrared spectra of xylylene isomers in the gas phase, using free electron laser (FEL) radiation. All xylylenes were generated by flash pyrolysis. The IR spectra were obtained by monitoring the ion dip signal, using a IR/UV double resonance scheme. A gas phase IR spectrum of para‐xylylene  was recorded, whereas ortho‐ and meta‐xylylene were found to partially rearrange to benzocyclobutene and styrene. Computations of the UV oscillator strength  for all molecules were carried out and provde an explanation for the observation of the isomerization products. KW - biradicals KW - high-temperature chemistry KW - IR spectroscopy KW - pyrolysis KW - xylylene Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-218316 VL - 21 IS - 14 SP - 1515 EP - 1518 ER -