Discipline: Chemistry and Chemical Sciences
Subcategory: Chemistry (not Biochemistry)
Marco S. Messina - University of California, Los Angeles
Co-Author(s): Jonathan C. Axtell, Yiqun Wang, Paul Chong, Alex I. Wixtrom, Kent O. Kirlikovali, Brianna M. Upton, and Bryan M. Hunter, UCLA, Los Angeles, CA
We report the discovery that perfunctionalized icosahedral dodecaborate clusters of the type B12(OCH2Ar)12 (Ar = Ph or C6F5) can undergo photo-excitation with visible light, leading to a new class of metal-free photooxidants. Excitation in these species occurs as a result of the charge transfer between low-lying orbitals located on the benzyl substituents and an unoccupied orbital delocalized throughout the boron cluster core. Here we show how these species, photo-excited with a bench-top blue LED source, can exhibit excited-state reduction potentials as high as 3 Volts and can participate in electron-transfer processes with a broad range of styrene monomers, initiating their polymerization. Initiation is observed in cases of both electron-rich and electron-deficient styrene monomers at cluster loadings as low as 0.05 mol%. Furthermore, photo-excitation of B12(OCH2C6F5)12 in the presence of a less activated olefin such as isobutylene results in the production of highly branched poly(isobutylene). This work introduces a new class of air-stable metal-free photoredox reagents capable of mediating chemical transformations.
Funder Acknowledgement(s): A.M.S. thanks UCLA Department of Chemistry and Biochemistry for start-up funds and 3M for a Non-Tenured Faculty Award. M.S.M. thanks the NSF for the Bridge-to-Doctorate and the Predoctoral (GRFP) Fellowships. H.B.G. and O.S.S. acknowledge funding from the NIH (DK019037) and the Arnold and Mabel Beckman Foundation. A.N.A. thanks the NSF CAREER Award CHE-1351968. Y.W. thanks the CSST Scholarship. H.D.M. thanks the NSF (CHE-1507735) for funding. B.M.U. thanks UCLA for a Dissertation Year Fellowship.
Faculty Advisor: Alexander M. Spokoyny, email@example.com
Role: Being the lead author on this publication, I oversaw all aspects of the work which involved keeping in constant contact with all of our collaborators, and had a hand in many of the experiments. My main tasks involved synthesis of photooxidants, experiment design, many of the polymerizations and control experiments of those polymerizations. I was also in charge of developing all figures for the manuscript as well as typing of the manuscript which was published in the Journal of the American Chemical Society.