Molecular Design Of Organic Nonlinear Optical Materials

The equilibrium geometry of fullerene C62 was obtained with B3LYP/6-31G method. The IR spectrum and the thermodynamics functions were calculated based on the vibrational analysis. The electronic spectrum of C62 was examined using time-dependent B3LYP/3-21G method, and the result showed that there was characteristic absorption at 464nm and 548nm. The 13C NMR spectrum showed that there are 17 kinds of carbons in C62 due to low symmetry. On the basis of PM3/TDHF method, the first- and second-order hyperpolarizabilities of C62 were calculated to be 1.56?0~30esu and 43.18 X 10~36esu respectively when the frequency of the external electronic field was zero.The equilibrium geometries of squaraines substituted by heteropentacyclic, benzo fuzed heteropentacyclic, heterohexacyclic, benzo fuzed heterohexacyclic, heptacyclic, benzo fuzed heteroheptacyclic and zwitterionic squaraines were obtained with ab initio calculation at HF/6-31G* level and the electronic spectra were examined using CIS/6-31G* method. The linear polarizabilities, the first- and second-order hyperpolarizabilities of these squaraines were calculated using TDHF/6-31G* method in order to study the relationship between molecular structures and nonlinear optical properties, and the first-order hyperpolarizabilities of some squaraines had been explained by two-states model.Two optimized geometries of l,3-bia(4-amino-phenyl) squaraine dimers were obtained with B3LYP/6-31G* method. The molecular interaction energies of the dimers were corrected by basis set superposition errors- at B3LYP/6-311++G level and the result showed that the dimer which had centro-symmetrical structure was more stable than the dimer which had noncentro-symmetrical structure. The difference of electronic spectra of the dimers were examined using time dependent B3LYP/6-31G* method. In the end the linear and nonlinear optical properties were studied by TDHF/6-3 lG*metod.