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Title
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Functionalized picolinium quinodimethane chromophores for electro-optics: synthesis, aggregation behavior, and nonlinear optical properties
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Author
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Abstract
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| A new series of functionalized and thermally stable zwitterionic picolinium (dicyano)esterquinodimethane (PeQDM) chromophores have been synthesized in one step from 7,8-di(methoxycarbonyl)-7,8-dicyanoquinodimethane (DMCQ) and various picolinium salts in methanol in nearly 50% overall yields. Hyper-Rayleigh scattering (HRS) measurements at 1.07 Êm show very large near-resonant molecular first hyperpolarizabilities À up to 1800 ~ 10−30 esu, despite the fact that, compared to previously studied zwitterionic NLO chromophores, one of the strong CN acceptor groups is substituted by a weaker ester group to allow for further functionalization. The ester functionality can be further utilized for attachment of solubility-imparting groups, cross-linkers, and reactive groups for grafting the chromophore onto a polymer. To optimize the electro-optic (EO) activity in the polymer matrix, the aggregation behavior of the PeQDM chromophores is studied. X-ray crystallographic analysis confirms the charge-separated ground-state of PeQDM and reveals the formation of a face-to-face, antiparallel H-aggregation with a large slip angle (Æ = 64.5) between the chromophores. In a less polar polymer matrix, PeQDM chromophores can form H- and/or J-aggregates and only J-aggregates could contribute to the EO activity if the monomeric chromophores released during the thermally induced J−H transformation could be captured and effectively poled. In a more polar polymer host, chromophores are well dissolved as monomers and effectively poled. A large and stable EO activity (r33 = 110 pm/V) has been achieved with a polyethersulfone film doped with 5 wt % of N-benzyl picolinium (dicyano)esterquinodimethane (PeQDM-Ben). |
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Language
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English
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Source (journal)
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Chemistry of materials / American Chemical Society. - Washington, D.C., 1989, currens
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Publication
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Washington, D.C.
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2008
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ISSN
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0897-4756
[print]
1520-5002
[online]
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DOI
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10.1021/CM802341J
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Volume/pages
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20
:24
(2008)
, p. 7465-7473
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ISI
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000261800700016
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Full text (Publisher's DOI)
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