Journal of Physical Chemistry A, Vol.120, No.41, 8075-8084, 2016
Quantum Dynamics Simulations of Excited State Energy Transfer in a Zinc-Free-Base Porphyrin Dyad
Rational design of artificial light-harvesting molecular architectures entails building systems that absorb strongly in the visible and near-IR region of the electromagnetic spectrum and also funnel excited state energy to a single site. The ability to model nonadiabatic processes, such as excited-state energy transfer (EET), that occur on a picosecond time scale can aid in the development of novel artificial light-harvesting arrays. A combination of density functional theory (DFT), time-dependent DFT, tight-binding molecular dynamics, and quantum dynamics is employed here to simulate EET in the ZnFb Phi dyad, a model artificial light harvesting array that undergoes EET with an experimentally measured rate constant of (3.5 ps)(-1) upon excitation at 550 nm in toluene [Yang et al. J. Phys. Chem. B 1998, 102, 9426-9436]. We find that to successfully simulate the EET process, it is important to (1) include coupling between nuclear and electronic degrees of freedom in the QD simulation, (2) account for Coulomb coupling between the electron and hole wavepackets, and (3) parametrize the extended Huckel model Hamiltonian employed in the QD simulations with respect to the DFT.