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The first hyperpolarizability ofthe four trans forms of a dithienyletheneindolinooxazolidine biphotochrome in acetonitrile solution has beenevaluated by using two solvation models, an explicit and an implicitone. The implicit solvation model is the integral equation formalismof the polarizable continuum model (IEF-PCM), whereas in the explicitone, the solvent molecules are represented by point charges, of whichthe positions have been generated by Monte Carlo simulations whereasthe solute is treated quantum mechanically. At optical frequencies,first hyperpolarizabilities calculated with the implicit solvationmodel are usually larger than those obtained with the multiscale approach.However, both approaches predict similar contrasts, indicating thatimplicit solvation models such as IEF-PCM are well-suited to describethe variations in the NLO responses of molecular switches. In addition,the analysis of the contrasts of first hyperpolarizabilities showsthat the biphotochrome can act as a three-state NLO switch. [ABSTRACT FROM AUTHOR]

Molecular dynamics (MD) simulations have been coupled to valence bond/Hartree−Fock (VB/HF) quantum-chemical calculations to evaluate the impact of diagonal and off-diagonal disorder on charge carrier mobilities in self-assembled one-dimensional stacks of a perylene diimide (PDI) derivative. The relative distance and orientation of the PDI cores probed along the MD trajectories translate into fluctuations in site energies and transfer integrals that are calculated at the VB/HF level. The charge carrier mobilities, as obtained from time-of-flight numerical simulations, span several orders of magnitude depending on the relative time scales for charge versus molecular motion. Comparison to experiment suggests that charge transport in the crystal phase is limited by the presence of static defects. [ABSTRACT FROM AUTHOR]