@article{FriedlRengerBerlepschetal.2016,
  author    = {Friedl, Christian and Renger, Thomas and Berlepsch, Hans V. and Ludwig, Kai and Schmidt am Busch, Marcel and Megow, J{\"o}rg},
  title     = {Structure Prediction of Self-Assembled Dye Aggregates from Cryogenic Transmission Electron Microscopy, Molecular Mechanics, and Theory of Optical Spectra},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {120},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.6b05856},
  pages     = {19416 -- 19433},
  year      = {2016},
  abstract  = {Cryogenic transmission electron microscopy (cryo-TEM) studies suggest that TTBC molecules self-assemble in aqueous solution to form single-walled tubes with a diameter of about 35 A. In order to reveal the arrangement and mutual orientations of the individual molecules in the tube, we combine information from crystal structure data of this dye with a calculation of linear absorbance and linear dichroism spectra and molecular dynamics simulations. We start with wrapping crystal planes in different directions to obtain tubes of suitable diameter. This set of tube models is evaluated by comparing the resulting optical spectra with experimental data. The tubes that can explain the spectra are investigated further by molecular dynamics simulations, including explicit solvent molecules. From the trajectories of the most stable tube models, the short-range ordering of the dye molecules is extracted and the optimization of the structure is iteratively completed. The final structural model is a tube of rings with 6-fold rotational symmetry, where neighboring rings are rotated by 30 and the-transition dipole moments of the chromophores form an angle of 74 with respect to the symmetry axis of the tube. This model is in agreement with cryo-TEM images and can explain the optical spectra, consisting of a sharp red-shifted J-band that is polarized parallel to to the symmetry axis of the tube and a broad blue-shifted H-band polarized perpendicular to this axis. The general structure of the homogeneous spectrum of this hybrid HJ-aggregate is described by an analytical model that explains the difference in redistribution of oscillator strength inside the vibrational manifolds of the J- and H-bands and the relative intensities and excitation energies of those bands. In addition to the-particular system investigated here, the present methodology can be expected to aid the structure prediction for a wide range of self-assembled dye aggregates.},
  language  = {en}
}
@article{Megow2016,
  author    = {Megow, J{\"o}rg},
  title     = {Computing dispersive, polarizable, and electrostatic shifts of excitation energy in supramolecular systems: PTCDI crystal},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {145},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4962179},
  pages     = {9},
  year      = {2016},
  abstract  = {The gas-to-crystal-shift denotes the shift of electronic excitation energies, i.e., the difference between ground and excited state energies, for a molecule transferred from the gas to the bulk phase. The contributions to the gas-to-crystal-shift comprise electrostatic as well as inductive polarization and dispersive energy shifts of the molecular excitation energies due to interaction with environmental molecules. For the example of 3,4,9,10-perylene-tetracarboxylic-diimide (PTCDI) bulk, the contributions to the gas-to-crystal shift are investigated. In the present work, electrostatic interaction is calculated via Coulomb interaction of partial charges while inductive and dispersive interactions are obtained using respective sum over states expressions. The coupling of higher transition densities for the first 4500 excited states of PTCDI was computed using transition partial charges based on an atomistic model of PTCDI bulk obtained from molecular dynamics simulations. As a result it is concluded that for the investigated model system of a PTCDI crystal, the gas to crystal shift is dominated by dispersive interaction. Published by AIP Publishing.},
  language  = {en}
}
@article{MegowKuleszaMay2016,
  author    = {Megow, J{\"o}rg and Kulesza, Alexander and May, Volkhard},
  title     = {A mixed quantum-classical description of pheophorbide a linear absorption spectra: Quantum-corrections of the Q(y)- and Q(x)-absorption vibrational satellites},
  series = {Chemical physics letters},
  volume    = {643},
  journal   = {Chemical physics letters},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0009-2614},
  doi       = {10.1016/j.cplett.2015.11.016},
  pages     = {61 -- 65},
  year      = {2016},
  abstract  = {The ground-state classical path approximation is utilized to compute molecular absorption spectra in a mixed quantum-classical frame. To improve the description for high-frequency vibrational satellites, related quantum correction factors are introduced. The improved method is demonstrated for the Q(y),and Q(x)-bands of pheophorbide a. (C) 2015 Elsevier B.V. All rights reserved.},
  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}
}