Effects on conformacional and molecular eletronical properties

Author(s)

Herbert de Castro Georg

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2006-07-10

Examining board members

Kaline Rabelo Coutinho; Antonio Carlos Borin; Rogério Custódio; Mario Jose de Oliveira; Antonio Jose Roque da Silva

• Advisor: Kaline Rabelo Coutinho

Abstract

The study oI\' the solvent effect on molecular properties is oI\' immense interest, both scienfic and technologic, since the activity oI\' molecular systems used as sensors, drug carriers, catalysers, optical devices, etc., not to mention the biological processes, depends on the medium where these molecular systems lie. ln the present work we dealt with the solvent effect in the electronic absorption spectrum oI\' three molecules (acrolein, benzophenone and p-dimetylarnino cinnamal dehyde) using the sequential QM/MM method. ln the first molecule we observed that water affects significantly its electronic levels, but the solvatochrornic shift on the n - ´pi´* band due to water is typical and can be described through the direct application on the sequential QM/MM method. ln the second molecule we observed the necessity of an additional procedure to describe the polarization of the solute molecule in solution and hence describe correctly the solute-solvent interaction potential. By means on this new process we were able to describe the solvent effect on the excitation energies of the molecule. The third molecule possesses a conjugate double bonds chain and showed a tendency to deform its geometry and produce a zwitterionic state in solution. Using the sequential QM/MM method, allied to the solute polarization procedure, we were able to infer the structure of\' this molecule in water through the solvatocrornic shift it suffers. (AU)