Boron Difluoride Formazanate Copolymers with 9,9-Di-n-hexylfluorene Prepared by Copper-Catalyzed Alkyne-Azide Cycloaddition Chemistry

Authors

Stephanie M. Barbon
Joe GilroyFollow

Document Type

Article

Publication Date

Spring 5-5-2016

Journal

Polymer Chemistry

Volume

7

First Page

3589

Last Page

3598

URL with Digital Object Identifier

DOI: 10.1039/C6PY00441E

Abstract

The synthesis and characterization of copolymers based on boron difluoride formazanate (BF₂L) and 9,9-di-n-hexylfluorene (hex₂Fl) units are described. A series of model compounds [(BF₂L)-(hex₂Fl), (hex₂Fl)-(BF₂L)-(hex₂Fl), and (BF₂L)-(hex₂Fl)-(BF₂L)] were also studied in order to fully understand the spectroscopic properties of the title copolymer [(BF₂L)-(hex₂Fl)]_n. The model compounds and copolymers, which were synthesized by copper catalyzed alkyne-azide cycloaddition chemistry, exhibited high molar absorptivities (25,700-54,900 M^-1 cm^-1), large Stokes shifts (123-143 nm, 3590-3880 cm^-1), and tunable electrochemical behaviour (E°_red1 ca. -0.75 V and E°_red2 ca. -1.86 V vs. ferrocene/ferrocenium). The low-energy wavelength of maximum absorption and emission of the model compounds red-shifted relative to the BF₂L repeating unit by ca. 30 nm per triazole ring formed, to maximum values of 557 nm and 700 nm in DMF, respectively. The low-energy absorption and emission properties of the copolymer were consistent with the model compound bearing two triazole rings [(hex₂Fl)-(BF₂L)-(hex₂Fl)] and were not dependant on copolymer molecular weight. However, the title copolymers may show promise as a light-harvesting material based on their thin-film optical band gap of 1.67 eV.