Fluorescent Difluoroboron bB-Diketonate Complexes: Synthesis and Photophysical Properties in Solution and Polylactide Media

Xu, Songpan, Department of Chemistry, University of Virginia
Fraser, Cassandra, Department of Chemistry, University of Virginia
Demas, James, Department of Chemistry, University of Virginia
Pu, Lin, Department of Chemistry, University of Virginia
Macdonald, Timothy, Department of Chemistry, University of Virginia

Difluoroboron -diketone complexes, BF bdks, have been widely investigated as photochemical reagents, two-photon dyes, and oxygen and mechanical sensors due to their fascinating emissive properties. To gain a better understanding of their emissive properties in both solution and polymer matrices, BF bdks with varying aromatic groups were synthesized and their photophysical properties were investigated in both methylene chloride and polylactide (PLA). We found that not only conjugation length and - aspell6-en-7.1-0 aspell6-en-7.1-0.tar.bz2 Base64.class Base64DecoderStream.class Base64DecoderStream.java Base64EncoderStream.class Base64EncoderStream.java Base64.java bin driverloop.sh getabstractfromOCRtext getabstractfrompdf getabstractfrompdf2 getabstractfrompdf3 getabstractfrompdf_ocr getabstractfrompdf_ocr2 getabstractfromTETtext getadvisor.perl getlangfrompdf2 getlangfromtext getmodelfromtabline getmodsfromtabline getpdffilenamefromtabline getpid getrawpdfpage gettextfrompdf2 langdetect libradryrun libraingest libraingest_bak libraingest.bak libraingestfromdir libraIngestLoop librasolrize META-INF outfile_p22-p36.pdf pdfminer-20110515 pdfminer-20110515.tar saxon9.jar splitter.perl sys_path_show.py tesseract-ocr tet toplevelloop.sh UVA_CD_migration_project_metadata-20140115_UTF-8.txt UVA_CD_migration_project_metadata.fnames.txt xdiff.jar xercesImpl-2.9.0.jar transitions but also intramolecular charge transfer (ICT) transitions influence the fluorescence properties. Asymmetric BF bdks, which have a greater difference in electron donating ability from the two sides, exhibit stronger ICT processes and longer fluorescence lifetimes. The results are also backed by computational chemistry, which reveals that for unsymmetrically substituted BF 2 bdks, the larger aromatic ring (i.e. stronger donor) can contribute more significantly to the HOMO, whereas the LUMO+1 extends over the whole molecule, including the diketonate core. Finally, substituent effects were also investigated; electron-donating methoxyl groups on the aromatic rings led to enhanced fluorescence quantum yields. The studies of emissive triplet states were also conducted for BF 2 bdk/PLA blends. In another study, one of these complexes, BF 2 dbmOMe, was further utilized as an emission color probe for solvent-free lactide ring-opening polymerization. It was found that when BF 2 dbmOMe is embedded in lactide monomer, the dye tends to form yellow-emissive clusters. When it added to a polymerization reaction, the system exhibited a yellow to blue color transition, accompanied by a decreasing trend in fluorescence lifetime as the dye began to dissolve and disperse in the polymer and the reaction progressed.

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MS (Master of Science)
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