title: Visible-Light-Induced Olefin Activation Using 3D Aromatic Boron-Rich Cluster Photooxidants.
abstract: We report a 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 benchtop blue LED source, can exhibit excited-state reduction potentials as high as 3 V 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 0.005 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 photo-redox reagents capable of mediating chemical transformations.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.|California NanoSystems Institute, University of California, Los Angeles , 570 Westwood Plaza, Los Angeles, California 90095-1569, United States.
authors.forename: Marco S
authors.initials: MS
authors.lastname: Messina
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Axtell
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Yiqun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Paul
authors.initials: P
authors.lastname: Chong
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Alex I
authors.initials: AI
authors.lastname: Wixtrom
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Kent O
authors.initials: KO
authors.lastname: Kirlikovali
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.|California NanoSystems Institute, University of California, Los Angeles , 570 Westwood Plaza, Los Angeles, California 90095-1569, United States.|Department of Bioengineering, University of California, Los Angeles , 410 Westwood Plaza, Los Angeles, California 90095-1600, United States.
authors.forename: Brianna M
authors.initials: BM
authors.lastname: Upton
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91115, United States.
authors.forename: Bryan M
authors.initials: BM
authors.lastname: Hunter
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91115, United States.
authors.forename: Oliver S
authors.initials: OS
authors.lastname: Shafaat
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Saeed I
authors.initials: SI
authors.lastname: Khan
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91115, United States.
authors.forename: Jay R
authors.initials: JR
authors.lastname: Winkler
authors.affiliation: Beckman Institute, California Institute of Technology , Pasadena, California 91115, United States.
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.|California NanoSystems Institute, University of California, Los Angeles , 570 Westwood Plaza, Los Angeles, California 90095-1569, United States.
authors.forename: Anastassia N
authors.initials: AN
authors.lastname: Alexandrova
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.|California NanoSystems Institute, University of California, Los Angeles , 570 Westwood Plaza, Los Angeles, California 90095-1569, United States.
authors.forename: Heather D
authors.initials: HD
authors.lastname: Maynard
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles , 607 Charles E. Young Drive East, Los Angeles, California 90095-1569, United States.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Spokoyny
mesh_terms: D001896:Boron Compounds / Q000737:chemistry* / Q000528:radiation effects; D004579:Electron Transport; D008027:Light; D008958:Models, Molecular; D015394:Molecular Structure; D016877:Oxidants / Q000737:chemistry*; D010084:Oxidation-Reduction; D055668:Photochemical Processes; D011090:Polyenes / Q000737:chemistry*; D058105:Polymerization; D011108:Polymers / Q000737:chemistry*
chemical_list: D001896:Boron Compounds; D016877:Oxidants; D011090:Polyenes; D011108:Polymers; C119788:dodecaborate; C008967:polyisobutylene