Electronic circular dichroism in exciton-coupled dimers: Vibronic spectra from a general all-coordinates quantum-dynamical approach Fabrizio, Santoro;1 1 Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy Abstract In recent years we contributed to the development of effective methods to compute electronic circular dichroism (ECD) lineshapes when nonadiabatic couplings are negligible [1-3]. Here we make a step toward the description of systems whose electronic states exhibit remarkable mixings, presenting a computational approach [4] to simulate the vibronic lineshapes of absorption and ECD spectra in exciton-coupled dimers [5]. Our method is based on a time-dependent expression of the spectra [6] that are computed though the quantum dynamics of suitable wave packets moving on coupled diabatic states localized on the monomers; it is general and straightforwardly applicable when the electronic potential energy surfaces of the monomer excitation can be described within harmonic approximation [4]. At variance with previous theoretical treatments [7, 8], our method allows to include the effect of all the vibrational modes of the system, accounting for geometry displacements, frequency changes and normal-modes (Duschinsky) mixing. This is possible exploiting a hierarchical representation of the Hamiltonian in blocks [9], defined so that few blocks (few coordinates) describe accurately the short-time dynamics (and hence the low- intermediate-resolution spectra) of the full system. The application to a "dimer" of anthracene (156 normal modes) delivers absorption and ECD spectra in the region of the 1La monomer transition in very nice agreement with the experiment [10]. Furthermore, the hierarchical representation allows the qualitative assignment of the main vibronic features of the spectra in terms of transitions to states of well-defined "effective" vibrational modes. References [1] Avila F, Santoro F, Phys Chem Chem Phys 2012; 14: 13459 [2] Santoro F, Barone V, Int J Quantum Chem 2010; 110:476 [3] Bloino J, Biczysko M, Santoro F, Barone V. J Chem Theor Comp 2010;6:1256 [4] Padula D, Picconi D, Di Bari L, Lami A, Pescitelli G, Santoro F, J Phys Chem submitted [5] Harada, N.; Nakanishi, K.; Berova, N. In Comprehensive Chiroptical Spectroscopy; Berova, N.; Woody, R. W.; Polavarapu, P.; Nakanishi, K., Eds.; Wiley: New York, 2012; 1:115 [6] Seibt, J.; Engel, V. The Journal of chemical physics 2007, 126:074110. [7] Pawlikowski, M.; Zgierski, M. Z. The Journal of Chemical Physics 1982, 76, 4789-4797 [8] Guthmuller, J.; Zutterman, F.; Champagne, B. The Journal of chemical physics 2009, 131: 154302 [9] Picconi, D.; Lami, A.; Santoro, F. The Journal of Chemical Physics 2012, 136: 244104 [10] Harada, N.; Takuma, Y.; Uda, H. Journal of the American Chemical Society 1978, 100, 4029
Electronic circular dichroism in exciton-coupled dimers: Vibronic spectra from a general all-coordinates quantum-dynamical approach
Fabrizio Santoro
2013
Abstract
Electronic circular dichroism in exciton-coupled dimers: Vibronic spectra from a general all-coordinates quantum-dynamical approach Fabrizio, Santoro;1 1 Consiglio Nazionale delle Ricerche - CNR, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), UOS di Pisa, Area della Ricerca, Via G. Moruzzi 1, I-56124 Pisa, Italy Abstract In recent years we contributed to the development of effective methods to compute electronic circular dichroism (ECD) lineshapes when nonadiabatic couplings are negligible [1-3]. Here we make a step toward the description of systems whose electronic states exhibit remarkable mixings, presenting a computational approach [4] to simulate the vibronic lineshapes of absorption and ECD spectra in exciton-coupled dimers [5]. Our method is based on a time-dependent expression of the spectra [6] that are computed though the quantum dynamics of suitable wave packets moving on coupled diabatic states localized on the monomers; it is general and straightforwardly applicable when the electronic potential energy surfaces of the monomer excitation can be described within harmonic approximation [4]. At variance with previous theoretical treatments [7, 8], our method allows to include the effect of all the vibrational modes of the system, accounting for geometry displacements, frequency changes and normal-modes (Duschinsky) mixing. This is possible exploiting a hierarchical representation of the Hamiltonian in blocks [9], defined so that few blocks (few coordinates) describe accurately the short-time dynamics (and hence the low- intermediate-resolution spectra) of the full system. The application to a "dimer" of anthracene (156 normal modes) delivers absorption and ECD spectra in the region of the 1La monomer transition in very nice agreement with the experiment [10]. Furthermore, the hierarchical representation allows the qualitative assignment of the main vibronic features of the spectra in terms of transitions to states of well-defined "effective" vibrational modes. References [1] Avila F, Santoro F, Phys Chem Chem Phys 2012; 14: 13459 [2] Santoro F, Barone V, Int J Quantum Chem 2010; 110:476 [3] Bloino J, Biczysko M, Santoro F, Barone V. J Chem Theor Comp 2010;6:1256 [4] Padula D, Picconi D, Di Bari L, Lami A, Pescitelli G, Santoro F, J Phys Chem submitted [5] Harada, N.; Nakanishi, K.; Berova, N. In Comprehensive Chiroptical Spectroscopy; Berova, N.; Woody, R. W.; Polavarapu, P.; Nakanishi, K., Eds.; Wiley: New York, 2012; 1:115 [6] Seibt, J.; Engel, V. The Journal of chemical physics 2007, 126:074110. [7] Pawlikowski, M.; Zgierski, M. Z. The Journal of Chemical Physics 1982, 76, 4789-4797 [8] Guthmuller, J.; Zutterman, F.; Champagne, B. The Journal of chemical physics 2009, 131: 154302 [9] Picconi, D.; Lami, A.; Santoro, F. The Journal of Chemical Physics 2012, 136: 244104 [10] Harada, N.; Takuma, Y.; Uda, H. Journal of the American Chemical Society 1978, 100, 4029I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
