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Dipyrrin complexes and their uses as self assembling materials

Benstead, Michael

Authors

Michael Benstead



Contributors

Georg H. Mehl
Supervisor

Abstract

Several series of BODIPYs bearing mesogenic substituents were synthesised and their fluorescence and liquid crystal properties were characterized. Each compound prepared consisted of one BODIPY fluorophore and one, two or three mesogenic units based primarily on a cyanobiphenyl core. Initially, the mesogens were attached to the pyrrolic positions of the fluorophore, but it was found that mesogen attachment at the BODIPY 8-phenyl ring gave an increased preference for mesophase formation due to the molecules having a more rod-like‘ (calamitic) shape. For several of the compounds, a monotropic nematic phase was exhibited, however, no layered phase (e.g. smectic) was observed. Several linker groups between the mesogenic unit and the fluorophore were investigated and it was found that linear linker groups (e.g. ethynyl) had a greater preference for liquid crystal phase formation when compared to non-linear linker groups (e.g. triazole).

Two series of di-mesogenic compounds were prepared and a significant stabilisation of the nematic phase was observed when compared to the mono-mesogenic analogues. The compounds bearing the mesogenic units on the 8-phenyl ring were prepared by metal-catalyzed couplings and each series consisted of three compounds with increasing alkyl substitution on the bipyrrolic core of the BODIPY. This resulted in a progressive increase in fluorescence quantum yield of the compounds in each series due to increased rotational restriction of the 8-phenyl ring along with a concurrent decrease in nematic phase stability. This permitted the observation of a structure-property relationship between nematic phase stability and fluorescence intensity. A BODIPY with significantly red-shifted fluorescence was also prepared and three mesogenic units were attached to this compound. Temperature dependant fluorescence measurements were taken in order to observe any relationship between fluorescence and degree of molecular ordering (e.g. nematic phase fluorescence compared to isotropic liquid fluorescence) and several of the compounds were dissolved in a commercial nematic liquid crystal and incorporated into a twisted nematic cell in order to observe the affect that molecular alignment (induced by an electric field) had on the fluorescence.

Citation

Benstead, M. (2010). Dipyrrin complexes and their uses as self assembling materials. (Thesis). University of Hull. Retrieved from https://hull-repository.worktribe.com/output/4210942

Thesis Type Thesis
Deposit Date Aug 15, 2011
Publicly Available Date Feb 22, 2023
Keywords Chemistry
Public URL https://hull-repository.worktribe.com/output/4210942
Additional Information Department of Chemistry, The University of Hull
Award Date Dec 1, 2010

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Copyright Statement
© 2010 Benstead, Michael. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder.




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