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The nonradiative relaxation of 9H-adenine was studied at the semiempirical OM2/MR-CI level using the surface-hopping approach. Geometry optimizations of energy minima and conical intersections as well as single-point calculations of excitation energies at critical points were performed to characterize the relevant potential energy surfaces of 9H-adenine and to assess the accuracy of the OM2 results. Surface-hopping calculations were performed to describe the nonradiative dynamics of 9H-adenine after vertical excitation into the optically active state. They showed that the deexcitation process is mainly governed by a two-step relaxation consisting of an ultrashort component and a longer component. These findings compare well with experimental results from time-resolved photoelectron spectroscopy. [ABSTRACT FROM AUTHOR]

Four trigonal topology compounds with three diarylamines redox centers and dibenzofulvene as core bridge have been synthesized. Their radical cations exhibit appealing intramolecular electron transfer pathways between three redox centers, depending on their position on the core bridge. By changing such positions (on either 2,7- or 3,6-), and the length of the bridge, the control of the intramolecular electron transfer pathways was achieved through the electron self-exchange route. These processes were investigated by absorption spectroscopy, electron paramagnetic resonance spectroscopy, and (time-dependent) density functional theory calculations. Hole mobility measurements were carried out as well, to correlate the intramolecular electron transfer with the hole-transporting ability for possible applications in optoelectronic devices.

Many applications in plasmonics are related to the coupling between metallic nanoparticles (MNPs) or between an emitter and a MNP. The theoretical analysis of such a coupling is thus of fundamental importance to analyze the plasmonic behavior and to design new systems. While classical methods neglect quantum and spill-out effects, time-dependent density functional theory (TD-DFT) considers all of them and with Kohn-Sham orbitals delocalized over the whole system. Thus, within TD-DFT, no definite separation of the subsystems (the single MNP or the emitter) and their couplings is directly available. This important feature is obtained here using the subsystem formulation of TD-DFT, which has been originally developed in the context of weakly interacting organic molecules. In subsystem TD-DFT, interacting MNPs are treated independently, thus allowing us to compute the plasmon couplings directly from the subsystem TD-DFT transition densities. We show that subsystem TD-DFT, as well as a simplified version of it in which kinetic contributions are neglected, can reproduce the reference TD-DFT calculations for gap distances greater than about 6 Å or even smaller in the case of hybrid plasmonic systems (i.e., molecules interacting with MNPs). We also show that the subsystem TD-DFT can be also used as a tool to analyze the impact of charge-transfer effects.

The nonradiative relaxation of 9H-adenine was studied at the semiempirical OM2/MR-CI level using the surface-hopping approach. Geometry optimizations of energy minima and conical intersections as well as single-point calculations of excitation energies at critical points were performed to characterize the relevant potential energy surfaces of 9H-adenine and to assess the accuracy of the OM2 results. Surface-hopping calculations were performed to describe the nonradiative dynamics of 9H-adenine after vertical excitation into the optically active state. They showed that the deexcitation process is mainly governed by a two-step relaxation consisting of an ultrashort component and a longer component. These findings compare well with experimental results from time-resolved photoelectron spectroscopy.

We have analyzed singlet and triplet excitation energies in oligothiophenes (up to five rings) using time-dependent density-functional theory (TD-DFT) with different exchange-correlation functionals and compared them with results from the approximate coupled-cluster singles and doubles model (CC2) and experimental data. The excitation energies have been calculated in geometries obtained by TD-DFT optimization of the lowest excited singlet state and in the ground-state geometries of the neutral and anionic systems. TD-DFT methods underestimate photoluminescence energies but the energy difference between singlet and triplet states shows trends with the chain-length similar to CC2. We find that the second triplet excited state is below the first singlet excited state for long oligomers in contrast with the previous assignment of Rentsch et al. (Phys.Chem. Chem. Phys. 1999, 1, 1707). Their photodetachment photoelectron spectroscopy measurements are better described by considering higher triplet excited states.