@article{daSilvaVarellaJonesetal.2019, author = {da Silva, Filipe Ferreira and Varella, Marcio T. do N. and Jones, Nykola C. and Hoffmann, Soren Vronning and Denifl, Stephan and Bald, Ilko and Kopyra, Janina}, title = {Electron-Induced Reactions in 3-Bromopyruvic Acid}, series = {Chemistry - a European journal}, volume = {25}, journal = {Chemistry - a European journal}, number = {21}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201806132}, pages = {5498 -- 5506}, year = {2019}, abstract = {3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum. The main fragmentation channel is the formation of Br- close to 0 eV and within several resonant features at 1.9 and 3-8 eV. At low electron energies, Br- formation proceeds through sigma* and pi* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser.}, language = {en} } @article{KuleszaTitovDalyetal.2016, author = {Kulesza, Alexander Jan and Titov, Evgenii and Daly, Steven and Wlodarczyk, Radoslaw and Megow, J{\"o}rg and Saalfrank, Peter and Choi, Chang Min and MacAleese, Luke and Antoine, Rodolphe and Dugourd, Philippe}, title = {Excited States of Xanthene Analogues: Photofragmentation and Calculations by CC2 and Time-Dependent Density Functional Theory}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {17}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201600650}, pages = {3129 -- 3138}, year = {2016}, abstract = {Action spectroscopy has emerged as an analytical tool to probe excited states in the gas phase. Although comparison of gas-phase absorption properties with quantum-chemical calculations is, in principle, straightforward, popular methods often fail to describe many molecules of interest-such as xanthene analogues. We, therefore, face their nano-and picosecond laser-induced photofragmentation with excited-state computations by using the CC2 method and time-dependent density functional theory (TDDFT). Whereas the extracted absorption maxima agree with CC2 predictions, the TDDFT excitation energies are blueshifted. Lowering the amount of Hartree-Fock exchange in the DFT functional can reduce this shift but at the cost of changing the nature of the excited state. Additional bandwidth observed in the photofragmentation spectra is rationalized in terms of multiphoton processes. Observed fragmentation from higher-lying excited states conforms to intense excited-to-excited state transitions calculated with CC2. The CC2 method is thus suitable for the comparison with photofragmentation in xanthene analogues.}, language = {en} } @article{Boese2015, author = {Boese, Adrian Daniel}, title = {Density Functional Theory and Hydrogen Bonds: Are We There Yet?}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {16}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {5}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201402786}, pages = {978 -- 985}, year = {2015}, abstract = {Density functional theory (DFT) has become more successful at introducing dispersion interactions, and can be thus applied to a wide range of systems. Amongst these are systems that contain hydrogen bonds, which are extremely important for the biological regime. Here, the description of hydrogen-bonded interactions by DFT with and without dispersion corrections is investigated. For small complexes, for which electrostatics are the determining factor in the intermolecular interactions, the inclusion of dispersion with most functionals yields large errors. Only for larger systems, in which van der Waals interactions are more important, do dispersion corrections improve the performance of DFT for hydrogen-bonded systems. None of the studied functionals, including double hybrid functionals (with the exception of DSD-PBEP86 without dispersion corrections), are more accurate than MP2 for the investigated species.}, language = {en} } @article{KlaperLinker2015, author = {Klaper, Matthias and Linker, Torsten}, title = {New Singlet Oxygen Donors Based on Naphthalenes: Synthesis, Physical Chemical Data, and Improved Stability}, series = {Chemistry - a European journal}, volume = {21}, journal = {Chemistry - a European journal}, number = {23}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {0947-6539}, doi = {10.1002/chem.201500146}, pages = {8569 -- 8577}, year = {2015}, abstract = {Singlet oxygen donors are of current interest for medical applications, but suffer from a short half-life leading to low singlet oxygen yields and problems with storage. We have synthesized more than 25new singlet oxygen donors based on differently substituted naphthalenes in only a few steps. The influence of functional groups on the reaction rate of the photooxygenations, thermolysis, half-life, and singlet oxygen yield has been thoroughly studied. We determined various thermodynamic data and compared them with density functional calculations. Interestingly, remarkable stabilities of functional groups during the photooxygenations and stabilizing effects for some endoperoxides during the thermolysis have been found. Furthermore, we give evidence for a partly concerted and partly stepwise thermolysis mechanism leading to singlet and triplet oxygen, respectively. Our results might be interesting for dark oxygenations and future applications in medicine.}, language = {en} } @article{GoetzeKroenerBanerjeeetal.2014, author = {Goetze, Jan P. and Kr{\"o}ner, Dominik and Banerjee, Shiladitya and Karasulu, Bora and Thiel, Walter}, title = {Carotenoids as a shortcut for chlorophyll Soret-to-Q band energy flow}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {15}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {15}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201402233}, pages = {3391 -- 3400}, year = {2014}, abstract = {It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1A(g)) and excited-state (1B(u)) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1B(u) minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.}, language = {en} } @article{LuoUtechtDokicetal.2011, author = {Luo, Ying and Utecht, Manuel Martin and Dokic, Jadranka and Korchak, Sergey and Vieth, Hans-Martin and Haag, Rainer and Saalfrank, Peter}, title = {Cis-trans isomerisation of substituted aromatic imines a comparative experimental and theoretical study}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {12}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {12}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201100179}, pages = {2311 -- 2321}, year = {2011}, abstract = {The cis-trans isomerisation of N-benzylideneaniline (NBA) and derivatives containing a central C=N bond has been investigated experimentally and theoretically. Eight different NBA molecules in three different solvents were irradiated to enforce a photochemical trans (hv) -> cis isomerisation and the kinetics of the thermal backreaction cis (Delta)-> trans were determined by NMR spectroscopy measurements in the temperature range between 193 and 288 K. Theoretical calculations using density functional theory and Eyring transition-state theory were carried out for 12 different NBA species in the gas phase and three different solvents to compute thermal isomerisation rates of the thermal back reaction. While the computed absolute rates are too large, they reveal and explain experimental trends. Time-dependent density functional theory provides optical spectra for vertical transitions and excitation energy differences between trans and cis forms. Together with isomerisation rates, the latter can be used to identify "optimal switches" with good photochromicity and reasonable thermal stability.}, language = {en} } @article{BaranacStojanovicKochKleinpeter2012, author = {Baranac-Stojanovic, Marija and Koch, Andreas and Kleinpeter, Erich}, title = {Density Functional Calculations of the Anisotropic Effects of Borazine and 1,3,2,4-Diazadiboretidine}, series = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, volume = {13}, journal = {ChemPhysChem : a European journal of chemical physics and physical chemistry}, number = {17}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1439-4235}, doi = {10.1002/cphc.201200732}, pages = {3803 -- 3811}, year = {2012}, abstract = {On the basis of the nucleus-independent chemical shift (NICS) concept, the anisotropic effects of two inorganic rings, namely, borazine and planar 1,3,2,4-diazadiboretidine, are quantitatively calculated and visualized as isochemical shielding surfaces (ICSSs). Dissection of magnetic shielding values along the three Cartesian axes into contributions from s and p bonds by the natural chemical shieldingnatural bond orbital (NCSNBO) method revealed that their appearance is not a simple reflection of the extent of (anti)aromaticity.}, language = {en} }