Theoretical Study Of Electron Transfer For Organic Systems By First-principles And Quantum Dynamics

Two kinds of electron transfer (ET) processes in different organic systems are investigated based on first-principles and quantum dynamics methods. One is the intramolecular ET reaction in solution, the other is the charge transport in organic semiconductor.For the intramolecular ET reaction in solution, we take a charge localized intervalence radical cation of a bis(hydrazine) as an example. A variety of ab initio approaches are employed to calculate ET parameters, reorganization energy, electronic coupling and effective frequency, and their validity are also discussed for this system. With use of the obtained parameters, the extend Sumi-Marcus reaction-diffusion theory is adopted to predict the ET rates. The results manifest that the ET rates of three isomers are agreement with the ESR experiment quite well while the rate of the left one is about 1000 times larger than the experimental one. Because of the limitation of ESR experiment, this large rate cannot be measured. Thus, one expects that new techniques have to be used to further investigate it.For the charge transport in organic semiconductor, we have investigated non-Condon effect on the charge carrier mobility of organic semiconductor dithophene-tetrathiathiafulvalene (DT-TTF) crystal. The first-principles calculations reveal that only several high-frequency intramolecular modes dominate the reorganization energy. The nuclear-coordinate dependence of electronic coupling prefers to perform an exponential or Gaussian property for most intermolecular modes rather than a linear one. At the same time, the electronic coupling, which is calculated with the reduced two-state model, of an isolated DT-TTF dimer is indeed affected by the surrounding molecules. Under the hopping mechanism with the nuclear tunneling incorporated, the mobility displays the band-like property. The predicted non-Condon mobility is always greater than that from Condon approximation. Furthermore, we find that the non-Condon dynamic disorder is not important for DT-DDT crystal, which is also confirmed by molecular dynamics simulation.