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Synthesis of Selectively 4-Substituted 9,9´-Spirobifluorenes and Modulation of Their Photophysical Properties.

Abstract

Synthesis of selectively 4-substituted 9,9’-spirobifluorenes was accomplished by using catalytic [2+2+2]-cyclotrimerization of specifically substituted diynols with alkynes to the corresponding fluorenols. Further synthetic transformations provided target molecules. Measurement of photophysical properties of the prepared 4-substituted 9,9’-spirobifluorenes revealed that emission maxima depended on electronic properties of the substituents present in the para position: the presence of electron accepting group strongly favored the maxima red shift toward the blue VIS region (CF3 λmax = 361 nm vs MeO λmax = 330 nm). Adding further substituents (aryl or arylethynyl moieties) on the phenyl ring in the position 4 did not exert a dramatic improvement on the emission maxima (CF3C6H4, λmax = 369 nm, CF3C6H4C≡C, λmax = 370 nm), but increased considerably quantum yields. In addition, a series of 9,9’-spirobifluorenes possessing various extended π-systems (pyrene, anthracene, etc.) was synthesized. In general, the emission maxima pattern reflected that of the parent π-systems, but they were red shifted by 10~30 nm. Finally, also a 1-[4-(9,9'-spirobifluorene-4-yl)phenyl]-2-aryl-ortho-carborane was prepared. These data thus may provide guidelines for further design of 9,9’-spirobifluorenes with taylored properties.

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Publication details

The article was received on 30 May 2017, accepted on 16 Jun 2017 and first published on 16 Jun 2017


Article type: Paper
DOI: 10.1039/C7OB01319A
Citation: Org. Biomol. Chem., 2017, Accepted Manuscript
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    Synthesis of Selectively 4-Substituted 9,9´-Spirobifluorenes and Modulation of Their Photophysical Properties.

    R. P. Kaiser, J. Mosinger, I. Cisarova and M. Kotora, Org. Biomol. Chem., 2017, Accepted Manuscript , DOI: 10.1039/C7OB01319A

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