Synthesis and Optical Studies of Organoboron Compounds
type: CreativeWork
description: Four-coordinate aryl borafluorenes with boron-oxygen and boron-nitrogen dative bondswere recently found to exhibit very large fluorescence Stokes shifts. The large Stokes shifts arehypothesized to arise from cleavage of the boron-donor dative bond in the excited state, via amechanism called bond-cleavage-induced intramolecular charge transfer (BICT). The primarygoal of this current investigation is to directly observe the BICT state by performing transientabsorption spectroscopy on four-coordinate borafluorenes which have improved optical stability.A family of four-coordinate borafluorenes was synthesized, each containing a dative B-O bondand two tert-butyl moieties on the aryl ring. Transient absorption spectroscopy (TAS) of the newborafluorenes showed existence of a single species in the excited state that is consistent with theBICT state. The TAS data is supported by fluorescence lifetime measurements and DFTcalculations.In 2016, Higuchi reported photochromic boronium-bipyridine complexes. It washypothesized that the photochromism arose from radical species that form via the photooxidationof iodide and other anions by the boronium cations. Although EPR data was provided to supportthis hypothesis, the EPR data was inconsistent with that expected for the proposed iodineradicals and boron center radicals. In the present work, boronium-bipyridine complexes withdifferent counter anions were synthesized to gain an understanding of how the anion affects thephotochromic properties of boronium-bipyridine complexes. EPR spectroscopy was employedto observe radicals generated on the complexes and further clarify the mechanism behind thephotochromic properties. The boronium-bipyridine complexes exhibited nearly identical radicalsignals to one another by EPR spectroscopy, however there was no evidence of radical formationon the anion, suggesting the reduction of the complex is occurring through a differentmechanism.The first polymer with pendant boronium-bipyridine complexes w…
abstract: Four-coordinate aryl borafluorenes with boron-oxygen and boron-nitrogen dative bondswere recently found to exhibit very large fluorescence Stokes shifts. The large Stokes shifts arehypothesized to arise from cleavage of the boron-donor dative bond in the excited state, via amechanism called bond-cleavage-induced intramolecular charge transfer (BICT). The primarygoal of this current investigation is to directly observe the BICT state by performing transientabsorption spectroscopy on four-coordinate borafluorenes which have improved optical stability.A family of four-coordinate borafluorenes was synthesized, each containing a dative B-O bondand two tert-butyl moieties on the aryl ring. Transient absorption spectroscopy (TAS) of the newborafluorenes showed existence of a single species in the excited state that is consistent with theBICT state. The TAS data is supported by fluorescence lifetime measurements and DFTcalculations.In 2016, Higuchi reported photochromic boronium-bipyridine complexes. It washypothesized that the photochromism arose from radical species that form via the photooxidationof iodide and other anions by the boronium cations. Although EPR data was provided to supportthis hypothesis, the EPR data was inconsistent with that expected for the proposed iodineradicals and boron center radicals. In the present work, boronium-bipyridine complexes withdifferent counter anions were synthesized to gain an understanding of how the anion affects thephotochromic properties of boronium-bipyridine complexes. EPR spectroscopy was employedto observe radicals generated on the complexes and further clarify the mechanism behind thephotochromic properties. The boronium-bipyridine complexes exhibited nearly identical radicalsignals to one another by EPR spectroscopy, however there was no evidence of radical formationon the anion, suggesting the reduction of the complex is occurring through a differentmechanism.The first polymer with pendant boronium-bipyridine complexes w…
author: Pennington, Michael Patrick
language: en_US
language: English
date published: 2024
date modified: 2026-07-27T18:44:23Z
provider: University of Alabama
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Alabama Libraries