Item
Voityuk, Alexander A.  
Comparison of donoracceptor electronic couplings calculated within twostate and threestate models suggests that the twostate treatment can provide unreliable estimates of Vda because of neglecting the multistate effects. We show that in most cases accurate values of the electronic coupling in a Ï€ stack, where donor and acceptor are separated by a bridging unit, can be obtained as á¹¼ da = (E2  E1) Î¼12 Rda + (2 E3  E1  E2) 2 Î¼13 Î¼23 Rda2, where E1, E2, and E3 are adiabatic energies of the ground, chargetransfer, and bridge states, respectively, Î¼ij is the transition dipole moments between the states i and j, and Rda is the distance between the planes of donor and acceptor. In this expression based on the generalized MullikenHush approach, the first term corresponds to the coupling derived within a twostate model, whereas the second term is the superexchange correction accounting for the bridge effect. The formula is extended to bridges consisting of several subunits. The influence of the donoracceptor energy mismatch on the excess charge distribution, adiabatic dipole and transition moments, and electronic couplings is examined. A diagnostic is developed to determine whether the twostate approach can be applied. Based on numerical results, we showed that the superexchange correction considerably improves estimates of the donoracceptor coupling derived within a twostate approach. In most cases when the twostate scheme fails, the formula gives reliable results which are in good agreement (within 5%) with the data of the threestate generalized MullikenHush model  
http://hdl.handle.net/2072/116925  
eng  
American Institute of Physics  
Tots els drets reservats  
AnÃ lisi numÃ¨rica
ElectrÃ²nica molecular Models matemÃ tics TransferÃ¨ncia de cÃ rrega Charge transfer Mathematical models Molecular electronics Numerical analysis 

Estimation of electronic coupling in Ï€ stacked donorbridgeacceptor systems: correction of the twostate model  
info:eurepo/semantics/article  
Recercat 