Compact representation of generalized molecular polarizabilities and efficient calculation of polarization energy in an arbitrary electric field

Generalized polarizabilities and the molecular charge distribution can describe the response of a molecule in an arbitrary static electric field up to second order. Depending on the expansion functions used to describe the perturbing potential, the generalized polarizability matrix can have rather large dimension (~1000). This matrix is the discretized version of the density response function or electronic susceptibility. Diagonalizing and truncating it can lead to significant (over an order of magnitude) speed-up in simulations. We have analyzed the convergence behavior of the generalized polarizability using a plane wave basis for the potential. The eigenfunctions of the generalized polarizability matrix are the natural polarization potentials. They are potentially useful to construct efficient polarizability models for molecules.

Intramolecular Photo-Oxidation as a Potential Source to Probe Biological Electron Damage: A Carboxylated Adenosine Analogue as Case Study

A carboxylated adenosine analog (C-Ado−) has been synthesized and probed via time-resolved photoelectron spectroscopy in order to induce intra-molecular charge transfer from the carboxylic acid moiety to the nucleobase. Intra-molecular charge transfer can be exploited as starting point to probe low-energy electron (LEE) damage in DNA and its derivatives. Time-dependent density functional theory (TD-DFT) calculations at the B3LYP-6311G level of theory have been performed to verify that the highest occupied molecular orbital (HOMO) was located on carboxylic acid and that the lowest occupied molecular orbital (LUMO) was on the nucleobase. Hence, the carboxylic acid could work as electron source, whilst the nucleobase could serve the purpose of electron acceptor. The dynamics following excitation at 4.66 eV (266 nm) were probed using time-resolved photoelectron spectroscopy using probes at 1.55 eV (800 nm) and 3.10 eV (400 nm). The data show rapid decay of the excited state population and, based on the similarity of the overall dynamics to deoxy-adenosine monophosphate (dAMP–), it appears that the dominant decay mechanism is internal conversion following 1ππ* excitation of the nucleobase, rather than charge-transfer from the carboxylic acid to the nucleobase.

Microscopic Insights into Charge Formation and Energetics in N-Doped Organic Semiconductors

<p>In the molecular doping of organic semiconductors</p><p>(OSC), achieving efficient charge generation</p><p>and managing the energetic cost for charge</p><p>release from local molecular charge transfer</p><p>complexes (CTCs) to the host matrix is of</p><p>central importance. Experimentally tremendous</p><p>progress has been made in this direction.</p><p>However, the relation between OSC film</p><p>structure on a nanoscopic level including different</p><p>inter-molecular geometrical arrangements</p><p>and the macroscopic properties of doped OSC</p><p>films is usually only established quite indirectly.</p><p>Explicit microscopic insights into the underlying</p><p>doping mechanisms and resulting electronic</p><p>structure are still scarce and mostly limited</p><p>to the study of the individual molecular constituents</p><p>or isolated bi-molecular dopant:host</p><p>complexes. In the present study we investigate</p><p>n-type doping of the frequently investigated</p><p>OSC materials ZnPC and F8ZnPc and</p><p>their mixtures which are n-doped with 2-Cyc-</p><p>DMBI. We report significant electronic differences</p><p>for complexes with nominally the same</p><p>material composition but different geometrical</p><p>structures. One specific important finding in</p><p>this context is that complexes containing two</p><p>adjacent dopant molecules show much reduced</p><p>ionization energy values, leading to substantially</p><p>reduced energy cost for charge release. Furthermore our results demonstrate that important</p><p>trends towards macroscopic system behavior</p><p>can already be obtained with increasing</p><p>size and varying composition of the relatively</p><p>small molecular dopant-host complexes considered,</p><p>including systematic shifts in the Fermi</p><p>level energies in the doped OSC.</p>

Microscopic Insights into Charge Formation and Energetics in N-Doped Organic Semiconductors

<p>In the molecular doping of organic semiconductors</p><p>(OSC), achieving efficient charge generation</p><p>and managing the energetic cost for charge</p><p>release from local molecular charge transfer</p><p>complexes (CTCs) to the host matrix is of</p><p>central importance. Experimentally tremendous</p><p>progress has been made in this direction.</p><p>However, the relation between OSC film</p><p>structure on a nanoscopic level including different</p><p>inter-molecular geometrical arrangements</p><p>and the macroscopic properties of doped OSC</p><p>films is usually only established quite indirectly.</p><p>Explicit microscopic insights into the underlying</p><p>doping mechanisms and resulting electronic</p><p>structure are still scarce and mostly limited</p><p>to the study of the individual molecular constituents</p><p>or isolated bi-molecular dopant:host</p><p>complexes. In the present study we investigate</p><p>n-type doping of the frequently investigated</p><p>OSC materials ZnPC and F8ZnPc and</p><p>their mixtures which are n-doped with 2-Cyc-</p><p>DMBI. We report significant electronic differences</p><p>for complexes with nominally the same</p><p>material composition but different geometrical</p><p>structures. One specific important finding in</p><p>this context is that complexes containing two</p><p>adjacent dopant molecules show much reduced</p><p>ionization energy values, leading to substantially</p><p>reduced energy cost for charge release. Furthermore our results demonstrate that important</p><p>trends towards macroscopic system behavior</p><p>can already be obtained with increasing</p><p>size and varying composition of the relatively</p><p>small molecular dopant-host complexes considered,</p><p>including systematic shifts in the Fermi</p><p>level energies in the doped OSC.</p>