| Optoelectronic research is on atomic or molecular excited-state structure and is correlated with their physical and chemical properties. Modem optoelectronic includes multiple subjects, such as organic optoelectronics, inorganic optoelectronics, supermolecular optoelectronics and biochemical optoelectronics etc. It is one of the important part of modern chemistry. Optical reaction is referred to the reactions after absorbing UV-Vis or infare spectra. Traditional optical chemistry is restricted in the absorbing of UV-Visible, but after the emergence of red laser devices that can make matters absorb multi-photon, infare optical chemistry is an important research area of optical chemistry. In our paper, organic luminescent materials, organic nonlinear optical materials and two-photon absorption materials are all theoretically studied using modern computational quantum chemistry.1. The semiempirical INDO/CI calculation were carried out to investigate the charge-transfer interaction and to evaluate the second-order opticalresponsibilities (B) for series I and II (-A, -B and -C) with rigid bridge of-CC-, -CONH- and -NHCO- respectively; The calculated values of p are 62.25, 154.80 and 178.13 (x10-30esu) for I-A, I-B and I-C with fullerene [60] as acceptor, and 7.14, 54.02 and 54.14 (xlO-30esu) for II-A, II-B and II-C with NIm as acceptor, respectively. The results indicate that for series I molecules, the nonlinear second-order optical responsibilities origin from the charge-transfer not only within the individual component moieties (ZnP and C60) but also between them (from donor-ZnP to acceptor-C60), comparativey for series II, the NLO response only comes from the charge transfer from the individual components (ZnP and NIm). The calculated results indicated that compared with 2D acceptor, the 3D acceptor, fullerene [60], because of the strong interactions, the effective center-to-center separation is significantly larger, leading to stronger NLO response. The calculated results also show that the bridge -NHCO- is more benefit to the charge-transfer than -CONH- and -CC-.2. With the INDO/SDCI-SOS method, we calculated the optical second-order nonlinearities of a series of donor-acceptor compound based on C60, the results showed that the introduction of thethienylethylene( s ) could enhance the NLO response, furthermore, with the substituent becoming larger i.e. increasing theconjugation length, the low-lying excited states, as well as the high-lying ones, have contributions to the NLO response. In these compounds C60 acts as the acceptor and charge transfers occur duringthe NLO response3. We have investigated the two-photon absorption cross-sections of 9,9-dimethyl fluorene and bifluorene-substituted compounds. The results indicated that from 9,9-dimethyl fluorene to 2,2-(9,9-dimethyl) bifluorene, the TPA cross sections were increased almost one order of magnitude larger which is caused by the coupling effects between the two monomers that is the main reasons for the enhancement of TPA cross section. Introduction of the strong substiruents, such as NO2 and NH2 (compound b4 and b6), will lead to the enhancement of the TPA cross section. Showing that bifluorene compounds with strong substituted groups are good candidates for the novel TPA materials.4. In this paper, we have theoretically studied the geometries, one- and two-photon absorptions of porphyrin and a series of carbaporphyrins in which the N atoms are substituted by C atoms gradually, using both TDDFT method and semi-empirical method INDO/CI. The TDDFT method, which has been proven to be an excellent alternative to the calculation of excitation energies, and the INDO/CI method is verified to be applicable for the investigated molecules. The calculated results indicated that the substitution of N atoms with C atoms not only lead to an enlargement of the center in geometry but also result in a red-shifting in the one-photon absorptions. And there is a significant difference in two-photon absorption properties between...
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