Non-linear Optical Chromophores

In conclusion, we first described the one step synthesis of nanoporous organosilica powders functionalized with a Non Linear Optical chromophore in the channel pore (azobenzene diethylphosphonate). These powders have been totally characterized and present a meso-porosity with a wormlike structure. Thin films monofunction-alised with NLO chromophore in the channel pores or bifunctionalized (NLO in the channel pores/erbium salt in the framework) were also prepared in one step and characterized by Grazing Incidence Small angle X-ray Scattering (GISAXS) and X-ray reflectivity. Interestingly, while the monofunctional thin film presents a lamellar structure, the bifunctional one (channel pores/framework)... 

O. K. Kim and J. M. Lehn, Solvatochromism of non-linear optical chromophores containing the dithienothiophene group in donor-acceptor molecules, Chem. Phys. Lett., 255, 147-150 (1996). 

Other very interesting PTs have recently been prepared including those containing liquid crystalline side chains [193], dicyanoPTs [194], and copolymers bearing side chain non-linear optical chromophores [195]. 

A direct relation between the first hyperpolarizability, of noncentrosy mmetric molecular structures and the centrosym-metricity content, 5(i), of such structures was shown for the first time in Ref. 5. For a series of systematic, in-plane distortions (stretch, pull, shift, and squish deformations) of the model non-linear optics chromophore benzene, a monotonic relationship between calculated values of f and 5(i) was found. The result suggests that the dominant variation in the hyperpolariz-ability for these structures arises from the change in oscillator strength. 

Another limitation of the silsesquioxane approach is evident when a non-linear optic NLO dye is used as the R group. For these chromophores, relaxation is dependent on the rigidity of the matrix. Their anchoring to one —SiOi 5 unit was found to be insufficient to achieve a highly cross-linked Si—O—Si network around the NLO chromophore and its relaxation could not be restricted. As a consequence, the order that is initially induced in the material by an electrical field pooling effect is lost upon ageing82 83. 

The term NLO-phore , meaning, bearer/producer of non-linear optics is preferred here to the often-used NLO-chromophore . 

Fig. 3.24 Examples of non-linear optical polymers with (a) pendent, (b) semi-buried and (c) backbone chromophores...

Non-linear optics in molecular materials has long been restricted to the investigation of organic chromophores. Most of the tin-based coordination compounds have been proposed only recently. Additionally, heavy atoms, such as tin, have also been used to enhance the optical-limiting response of metal phthalocyanines." Although this property derives from the cubic (a E ) NLO response, and falls outside the scope of the present review, it provides additional insights suggesting that tin-based coordination compounds could deserve more attention in the search for future NLO chromophores. 

Coe, B.J., Beyer, T., Jeffery, J.C., Coles, S.J., Gelbrich, T., Hursthouse, M.B.. Light, M.E. A spectroscopic, electrochemical and structural study of polarizable, dipolar ruthenium(II) arsine complexes as models for chromophores with large quadratic non-linear optical responses. J. Chem. Soc., Dalton Trans. 797-803 (2000)... 

Organometallic group 13 species investigated for non-linear optics are essentially limited to derivatives of the metalloid element, boron. A number of different organoboron systems have been used in NLO chromophores. We have described the use of 77-boratobenzene transition metal derivatives as acceptors in Section 12.04.1.2.2.(iii) and 12.04.1.2.2.(iv). In this section, we will discuss three-coordinate boranes, four-coordinate borates, and finally carboranes. 

Hui, C. Xiaohui, T. Yizhong, Y. Jiaping, L., Preparation of Polysiloxane with Pendant Cr-Bound Carbazole Chromophore for Non-Linear Optics. J. Appl. Polym. Sci. 2008,107,4076-4081. 

MOO 98] Moore A.J., Bryce M.R., Batsanov A.S. et al, New l,3-dithiol-2-ylidene donor-[small pi]-acceptor chromophores with intramolecular charge-transfer properties, and related donor-[small pi]-donor molecules synthesis, electrochemistry. X-ray crystal structures, non-linear optical properties and theoretical calculations , Journal of Materials Chemistry, vol. 8, no. 5, pp. 1173-1184, 1998. 

M. Lequan, R. M. Lequan, K. Chane-Ching, Trivalent boron as acceptor chromophore in asymmetrically substituted 4,4 -Biphenyl and azobenzene for non-linear optics. J. Mater. Chem. 1991, 1, 6, 997. 

Donor-acceptor (D-A) conjugated systems have been used for the obtention of molecular chromophores exhibiting non-linear optical response for which a strong intramolecular charge-transfer excitation is an indispensable prerequisite [149]. In these molecules, the electron transfer can be considered virtual because the D -A configuration is never reached [150]. On... 

Polymers interesting from the points of view of both non-linear optics and photoconductivity have been prepared by Wada and co-workers [223,224]. They have synthesized a series of head-to-tail polymers with dipolar carbazole chromophores [223]. The structures... 

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