Nonlinear optical chromophore derivatives

Considerable effort has been expended upon investigating the electronic absorption and fluorescence properties of carbazole derivatives or molecules containing a carbazole moiety/substructure, due to the interest of these compounds for application as nonlinear optical chromophores and as photoconducting materials. In the following, selection of papers is guided mainly by criteria of structural relevance, omitting very bulky molecules in which the carbazole unit is not prominent, or studies of luminescence properties. An overview of the electronic absorption spectra of carbazole derivatives is provided in Table 24. 

Two crosslinkable perfluorinated bisphenol A polymeric derivatives having nonlinear optical chromophores containing thiophene have been prepared. Both crosslinked polymers had higher Tg s and greater mechanical stability than their noncrosslinked analogues and were used as light-emitting diodes. 

An additional nonlinear optical copolymer derivative, (I), plasticizer, (11), and nonlinear optical chromophore, (111), were also prepared. 

Liu, S., M.A. Haller, H. Ma, L.R. Dalton, S.H. Jang, and A.K.Y. Jen. 2003. Focused microwave-assisted synthesis of 2,5-dihydrofuran derivatives as electron acceptors for highly efficient nonlinear optical chromophores. Adv Mater 15 603-607. 

Miller, R. D., Moylan, C. R., Reiser, 0., and Walsh, C. A., Heterocyclic azole nonlinear optical chromophores. 1. Donor-acceptor substituted pyrazole derivatives, Chem. Mater., 5, 625-632 (1993). 

The physical properties of the expanded radialenes were greatly enhanced upon donor functionalization, leading to the stable derivatives 76-78 with fully planar conjugated rr-chromophores [110]. These compounds exhibit large third-order nonlinear optical coefficients, can be reversibly reduced or oxidized, and... 

The theoretical models discussed above indicate that the sulfonyl group, although slightly weaker in electron acceptor strength, is indeed a viable alternative to the nitro group. In particular, sulfonyl derivatives of stilbene and azobenzene display large molecular hyperpolarizabilities and can be used as bifunctional chromophores for the construction of materials with nonlinear optical properties. 

Ferrocene-containing polymers with long spacers have been prepared as new nonlinear optical (NLO) materials for second harmonic generation (SHG) applications (e. g. frequency doubling) [10], The use of ferrocene derivatives in this area is attractive as a result of their demonstrated large hyperpolarizability values combined with their thermal and photochemical stabilities [11], These factors make polyferrocenes desirable candidates for use as processable NLO materials. The polyurethane copolymer 4.4 was synthesized using a functional ferrocene monomer (Eq. 4.1) and has been well-characterized the molecular weight was estimated by GPC to be Mn=7600. The two possible orientations of the ferrocene NLO chromophore monomer unit, which correspond to opposite dipole orientations, were both present in the main chain. 

Micron- and submicron-scale lateral structures of optically nonlinear organic films comprised of substituted trons-stilbene derivatives (Ri = OCH3, R2 = CN) was characterized [45]. Second harmonic generation (SHG), optical microscopy, and atomic force microscopy (AFM) were used in this investigation. The third-order nonlinear optical properties and two-photon absorption ofdifferent types of stilbene derivatives (D-tt-D, A-7t-A, D-7t-A) were investigated [46]. Using the INDO/CI method, the UV-vis spectra were explored and the position and strength of the two-photon absorption were predicted by sum-over-states expression. Relationships of the structures, spectra, and nonlinear optical properties have been examined. Two-photon absorption spectra (650-1000 nm) of a series of asymmetrically substituted stilbenoid chromophores... 

Because of the versatility of the polyurethane system it is possible to introduce comonomers which can affect the physical properties of the derived polymers. For example, photo cross-linkable polyurethanes are formulated using 2,5-dimethoxy-2,4 -diisocyanato stilbene as a monomer (76). Comonomers, having an azoaromatic chromophore, are used in optical bleaching applications (77), or in the formation of photorefractive polymers (78). The latter random poljnners have second-order nonlinear optical (NLO) properties. Linear poljnners are also obtained from HDI/PTMG and diacetylenic diols. These polymers can be cross-linked through the acetylenic linkages producing a network polymer with properties similar to poly(diacetylenes) (79). 

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