Synthesis of two-photon absorbing unsymmetrical branched chromophores through direct tris(bromomethylation) of fluorene

    Authors

    S. Yao;K. D. Belfield

    Comments

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    Abbreviated Journal Title

    J. Org. Chem.

    Keywords

    PHOTOPHYSICAL PROPERTIES; CONJUGATED POLYMERS; OPTICAL-PROPERTIES; LIGHT-EMISSION; DERIVATIVES; ABSORPTION; BLUE; COPOLYMERS; DENDRIMERS; MOLECULES; Chemistry, Organic

    Abstract

    Branched fluorene-based chromophores bearing electron-donating diphenylamino or electron-withdrawing nitro groups were synthesized as well as their linear analogues. An efficient synthetic method was developed via a novel 2,4,7-tris(bromomethyl)-9,9-diethylfluorene intermediate. The bromomethyl groups in this key intermediate were converted to either phosphonate or carboxaldehyde moieties, facilitating preparation of a high functionality branched structure. It was found that the reactivity at position 4 is attenuated in the bromomethyl and phosphorylated derivates, facilitating the selective and systematic functionalization of the fluorenyl system. All compounds were stable up to ca. 350 degrees C, except for a sterically crowded branched derivative. The linear optical properties of the compounds were investigated by UV-visible, steady-state fluorescence, and excitation anisotropy spectroscopic measurements. Fluorescence quantum yields were greater than or equal to 0.84 for symmetric linear and unsymmetric branched derivatives. Very high two-photon absorption (2PA) cross-sections were achieved (5765 GM at 520 nm and 4194 GM at 570 nm), as determined with use of picosecond and femtosecond laser excitation sources, respectively.

    Journal Title

    Journal of Organic Chemistry

    Volume

    70

    Issue/Number

    13

    Publication Date

    1-1-2005

    Document Type

    Article

    Language

    English

    First Page

    5126

    Last Page

    5132

    WOS Identifier

    WOS:000229982900028

    ISSN

    0022-3263

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