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Photo-induced Nitrogen and Carbon Based Radicals; A study on triplet nitrenes, triplet 1,2 and 1,3-biradicals

Ranaweera, Ranaweera Arachchilage Ajantha Upul

Abstract Details

2012, PhD, University of Cincinnati, Arts and Sciences: Chemistry.

This research project looked into different types of carbon and nitrogen based organic radicals. It summarizes following research studies.

1). Intramolecular sensitized triplet nitrene formation. 2). Efficient trans-cis isomerization through a 1,2-triplet biradical 3). Photo-induced 1,3-triplet biradical 4). Corannulene as a singlet oxygen generator and a singlet sensitizer 5). Ethynyl alcohols as a triplet sensitizer for 1-azidoadamantane 6). Stability and reactivity of carbon based radicals.

In Chapter 02, we look at alkylnitrenes with the focus of building high spin units. We demonstrated that geminal diazido alkane form high spin triplet iminenitrene (which is also a triplet 1,3-biradical) at cryogenic temperature but undergo mainly azido cleavage at ambient temperature.

In Chapter 03, we have analyzed the completion between the triplet nitrene formation and azido cleavage in azidomethylacetophenones using product studies, laser flash photolysis and Gaussian calculations.

In Chapter 04, we demonstrated that vinylketones undergo trans-cis isomerization via triplet 1,2-biradicals. We found the lifetime of the triplet 1,2-biradical varies from ~3 µs to 30 µs depending on the substituent group attached to the phenyl ring. Further, We showed that trans-cis isomerization via triplet-1,2-biradicals are efficient at cryogenic temperatures. We revealed the mechanism for the trans-cis isomerization using time resolved UV/Visible and time-resolved IR spectroscopy, matrix isolation and DFT calculations.

In Chapter 05, we have designed corannulene derivatives that can be used as singlet sensitizers. We have shown that these corannulene derivatives can be used to generate singlet oxygen from triplet oxygen.

In Chapter 06, we have utilized triplet-1,2-biradicals to form triplet vinylnitrene from vinyl azides. We found the lifetime of the triplet-1,2-biradical is ~5 µs for one vinyl azide where as the lifetime of the triplet vinyl nitrene could range from 4 – 12 µs depending on the substitution of the ring.

In Chapter 07, we studied the solid-state reactivity of the vinyl azides by performing laser flash photolysis of nanocrystals in water suspension, and correlated the kinetics and the crystal packing of the vinyl azides to explain the solid-state reactivity.

In Chapter 08, we demonstrated formation of triplet-1,3-biradicals through laser flash photolysis. We have shown that the lifetime of the triplet 1,3-biradical for the cyclopropyl phenyl ketones is ~2 µs.

In Chapter 09, we demonstrated that vinylketones with an electron withdrawing substituent like –C(O)OCH3 undergo trans-cis isomerization via triplet 1,2-biradicals. These molecules undergo 100% conversion into their cis-adduct upon irradiation.

In Chapter 10, we demonstrated the generation of a carbon based radical upon azido cleavage with small amount of triplet alkyl nitrene formation. This carbon based radical has a lifetime ~16 ms in argon-saturated solutions which increases upon the increase of oxygen concentration suggesting a formation of a peroxy radical.

In Chapter 11, we have shown that ethynyl alcohol derivatives can be used as a triplet sensitizer for 1-azidoadamantane. We have shown with product studies, laser flash photolysis, phosphorescence and DFT calculations that one out of the four ethynyl alcohols functions as a triplet sensitizer where as another functions as both triplet and singlet sensitizers.

Bruce Ault, PhD (Committee Chair)
Anna Gudmundsdottir, PhD (Committee Chair)
Thomas Beck, PhD (Committee Member)
Allan Pinhas, PhD (Committee Member)
711 p.

Recommended Citations

Citations

  • Ranaweera, R. A. A. U. (2012). Photo-induced Nitrogen and Carbon Based Radicals; A study on triplet nitrenes, triplet 1,2 and 1,3-biradicals [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337887740

    APA Style (7th edition)

  • Ranaweera, Ranaweera Arachchilage Ajantha Upul. Photo-induced Nitrogen and Carbon Based Radicals; A study on triplet nitrenes, triplet 1,2 and 1,3-biradicals. 2012. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337887740.

    MLA Style (8th edition)

  • Ranaweera, Ranaweera Arachchilage Ajantha Upul. "Photo-induced Nitrogen and Carbon Based Radicals; A study on triplet nitrenes, triplet 1,2 and 1,3-biradicals." Doctoral dissertation, University of Cincinnati, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1337887740

    Chicago Manual of Style (17th edition)