title: Acetylacetonate anchors for robust functionalization of TiO2 nanoparticles with Mn(II)-terpyridine complexes.
abstract: A novel class of derivatized acetylacetonate (acac) linkers for robust functionalization of TiO2 nanoparticles (NPs) under aqueous and oxidative conditions is reported. The resulting surface adsorbate anchors are particularly relevant to engineering photocatalytic and photovoltaic devices since they can be applied to attach a broad range of photosensitizers and photocatalytic complexes and are not affected by humidity. Acac is easily modified by CuI-mediated coupling reactions to provide a variety of scaffolds, including substituted terpy complexes (terpy = 2,2':6,2''-terpyridine), assembled with ligands coordinated to transition-metal ions. Since Mn-terpy complexes are known to be effective catalysts for oxidation chemistry, functionalization with Mn(II) is examined. This permits visible-light sensitization of TiO2 nanoparticles due to interfacial electron transfer, as evidenced by UV-vis spectroscopy of colloidal thin films and aqueous suspensions. The underlying ultrafast interfacial electron injection is complete on a subpicosecond time scale, as monitored by optical pump-terahertz probe transient measurements and computer simulations. Time-resolved measurements of the Mn(II) EPR signal at 6 K show that interfacial electron injection induces Mn(II) --> Mn(III) photooxidation, with a half-time for regeneration of the Mn(II) complex of ca. 23 s.
authors.affiliation: Department of Chemistry, Yale University, P.O. Box 208107, New Haven, Connecticut 06520-8107, USA.
authors.forename: William R
authors.initials: WR
authors.lastname: McNamara
authors.forename: Robert C
authors.initials: RC
authors.lastname: Snoeberger
authors.forename: Gonghu
authors.initials: G
authors.lastname: Li
authors.forename: James M
authors.initials: JM
authors.lastname: Schleicher
authors.forename: Clyde W
authors.initials: CW
authors.lastname: Cady
authors.forename: Macarena
authors.initials: M
authors.lastname: Poyatos
authors.forename: Charles A
authors.initials: CA
authors.lastname: Schmuttenmaer
authors.forename: Robert H
authors.initials: RH
authors.lastname: Crabtree
authors.forename: Gary W
authors.initials: GW
authors.lastname: Brudvig
authors.forename: Victor S
authors.initials: VS
authors.lastname: Batista
mesh_terms: D003198:Computer Simulation; D004578:Electron Spin Resonance Spectroscopy; D004583:Electrons; D006885:Hydroxybutyrates / Q000737:chemistry* / Q000528:radiation effects; D008027:Light; D008345:Manganese / Q000737:chemistry* / Q000528:radiation effects; D008567:Membranes, Artificial; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D053758:Nanoparticles / Q000737:chemistry* / Q000528:radiation effects; D009942:Organometallic Compounds / Q000737:chemistry* / Q000528:radiation effects; D010084:Oxidation-Reduction; D010316:Particle Size; D010422:Pentanones / Q000737:chemistry* / Q000528:radiation effects; D010777:Photochemistry; D016062:Porosity; D011725:Pyridines / Q000737:chemistry* / Q000528:radiation effects; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry* / Q000528:radiation effects; D014867:Water / Q000737:chemistry
chemical_list: D006885:Hydroxybutyrates; D008567:Membranes, Artificial; D009942:Organometallic Compounds; D010422:Pentanones; D011725:Pyridines; D014867:Water; C009495:titanium dioxide; C049529:acetyl acetonate; D008345:Manganese; D014025:Titanium