Item
Ministerio de Ciencia e InnovaciÃ³n (Espanya)  
Voityuk, Alexander A.  
Electronic coupling is a key parameter that controls the efficiency of excitation energy transfer (EET) and exciton delocalization. A new approach to estimate electronic coupling is introduced. Within a twostate model, the EET coupling V of two chromophores is expressed via the vertical excitation energies (Ei and Ej), transition dipole moments (Mi and Mj) of the system and transition moments (Î¼A and Î¼B) of the individual chromophores: V = (Ei E j){[(MiMj)(Î¼A 2 Î¼B 2) (Î¼AÎ¼B)(M i 2 Mj 2)]/[(Mi 2 Mj 2)2 + 4(MiM j)2]}. These quantities are directly available from quantum mechanical calculations. As the estimated coupling accounts for both shortrange and longrange interactions, this approach allows for the treatment of systems with short intermolecular distances, in particular, Ï€stacked chromophores. For a system of two identical chromophores, the coupling is given by V = (Ei Ej)[(EiFj E jFi)/(EiFj + EjF i)][1/(2 cos Î¸)] where Fi and Fj are the corresponding oscillator strengths and cos Î¸ is determined by the relative position of the chromophores in the dimer. Thus, the coupling can be derived from purely experimental data. The developed approach is used to calculate the EET coupling and exciton delocalization in two Ï€stacks of pyrimidine nucleobases 5â€²TT3â€² and 5â€²CT3â€² showing quite different EET properties Financial support from MICINN (Ministry of Science and Innovation, Spain) was provided by grant CTQ 201126573 

http://hdl.handle.net/2072/297359  
eng  
American Chemical Society (ACS)  
Tots els drets reservats  
ExcitaciÃ³ nuclear
Nuclear excitation QuÃmica de lâ€™estat excitat Excited state chemistry QuÃmica quÃ ntica Quantum chemistry 

Estimation of electronic coupling for singlet excitation energy transfer  
info:eurepo/semantics/article  
Recercat 