Environment Dependent Coherence of a Short DNA Charge Transfer System

Sim

2008

J. Phys. Chem. B

We explore distance dependent variation of the coherence length relevant to DNA charge-transfer processes within 5'-GAnG3-3' DNA sequences. Recently developed on-the-fly filtered propagator functional path integral approach was employed to sort out transport trajectories with significant contribution and to analyze correlation between electronic states. In particular, the coherence length was quantitatively determined through characteristics of off-diagonal quantum trajectories. Simulated coherence lengths and experimentally observed rate constants [Nature 2001, 412, 318] were found to be consistent such that, up to n = 2, the exponential decrease of the rate constants is associated with the donor-acceptor coherence driven charge transfer. In contrast, the rate constants become insensitive to the distance for n > or = 3 in which donor and acceptor are no longer significantly correlated. It was also found that the coherence within a collective state governs the overall charge transfer, which is composed of a part of a sequence within the coherence length from the donor.

Section: Resultsmentioning

confidence: 67%

Distance Dependent Coherence Variation in DNA Charge-Transfer Processes

Sim

2008

J. Phys. Chem. B

Coherence Length Determination of meso−meso Linked Porphyrin Arrays Based on Forward−Backward Pair Trajectory Analysis

Lee

et al. 2008

J. Phys. Chem. A

We investigated the excitation energy transfer process of meso-meso linked zinc(II) porphyrin arrays using the on-the-fly filtered propagator path integral method. Details of the dynamics such as coherence length of a porphyrin array are estimated by analysis of the characteristics of forward-backward pair trajectories. Upon examination of the convergence of the reduced density matrix with respect to the subset of Hilbert space trajectories, we determine the number of porphyrin units that form collective coherent states, that is, the coherence length. Simulation results show that the coherence length of zinc(II) porphyrin arrays is up to 4 units, which agrees excellently with experimental observations. On the other hand, the energy bias provided by the energy-accepting 5,15-bisphenylethynylated zinc(II) porphyrin reduces the degree of coherence which becomes negligible for an array with more than for porphyrin units. Considering conformational inhomogeneity, we found that the experimentally determined coherence length is the result of electronic and environmental influence rather than the structure disorder. Temperature dependence is also discussed.

Degree of Coherence of Single-Component Molecular Wires: Dependence on Length, Coupling Strength, and Dissipative Medium

Sim

2009

J. Phys. Chem. C

We present a simple formula for determining the degree of coherence of molecular wires in which a single type of molecular moieties are connected for efficient long-range quantum transport. Using the recently developed reduced trajectory space analysis in combination with the on-the-fly filtered propagator functional path integral formalism, the degree of coherence of molecular wires is quantified in terms of the coherence length, the number of strongly correlated molecular units. By performing simulations on various molecular wires, we found that there exists a simple and general formula for the coherence length as a function of the electronic coupling and the reorganization energy. More importantly, the formula is applicable to electronic as well as photonic transfer systems and, thus, allows straightforward and systematic prediction of the quantum transport mechanism on a quantitative basis.