Search

On the basis of ZINDO methods, according to the sum-overstates (SOS) expression, the program for the calculation of the second-order nonlinear optical susceptibilities βijk and βμ of molecules was devised, and the structures and nonlinear optical properties of unsymmetric bis(phenylethynyl) benzene series derivatives were studied. The influence of the molecular conjugated chain lengths, the donor and the acceptor on βμ was examined.

The equilibrium geometries and UV-visible spectra of a series of donor-C60 molecules were obtained by means of the AM1 and INDO/CI method, on the basis of accurate geometric and electronic structures. The nonlinear second-order optical polarizabilities were calculated using the method INDO/SDCI combined with the Sum-Over-States (SOS) expression. The calculated β (λ=1.34μm) values are 28.81, 48.56, 57.33, 66.99, 70.85, 85.84, and 142.14 (× 10–30 esu) for the molecules A, B, C, D, E, F and G, respectively. The frontier orbitals were plot for the representative molecules in order to exhibit the intramolecular charge transfer. The results indicate that introduction of thienylethylene can enhance the NLO response and the dimethylaniline-substituted dithienyl-ethylene-C60(molecule G) possesses the largest NLO second-order optical polarizability. The large β values can be attributed to the charge transfer between the substituents and C60, as well as within the three-dimensional conjugated sphere of C60.

The second-order nonlinear optical (NLO) properties of a series of benzothiazole derivatives were studied by use of the ZINDO-SOS method. These chromophores are formed by a donor-π-bridge-acceptor system, based on a nitro group connected with benzothiazole as the acceptor and a hydroxyl-functional amino group as the donor. For the purpose of comparison, we also designed molecules in which nitrobenzene is an acceptor. The calculation results indicate that benzothiazole derivatives exhibit larger second-order polarizabilities than nitrobenzene derivatives. In order to clarify the origin of the NLO response of these chromophores, their electron properties were investigated as well. The benzothiazole derivatives are good candidates for application in electro-optical device due to their high optical nonlinearities, good thermal and photonic stability.

The electronic structures, one-photon absorption (OPA) and two-photon absorption (TPA) properties of the azulenylporphyrins and azulene-fused porphyrins have been comparatively studied by using DFT/B3LYP/6-31G(d) and the ZINDO/SDCI method. With the number of azulenyl groups increasing, the OPA wavelengths of all molecules are red-shifted in 400{600 nm and the two-photon absorption cross section is gradually enlarged. The azulene-fused structures facilitate an expanding conjugated area and increasing TPA cross section. The origin of TPA properties of studied compounds is studied with a two-level model. In summary, the azulene-fused porphyrins exhibit strong two-photon absorption.

Using density functional theory and the semiempirical ZINDO method, we have investigated the equilibrium geometries, electronic spectra, and the second and third hyperpolarizabilities of C 74 and the metallofullerene Ca@C 74 . Theory predicts that Ca@C 74 has greater stability than C 74 and that the UV–Vis spectrum of Ca@C 74 shifts to the blue. Both species possess relatively large β μ values and thus are promising as nonlinear optical materials.