title: Evidence for Interfacial Halogen Bonding.
abstract: A homologous series of donor-π-acceptor dyes was synthesized, differing only in the identity of the halogen substituents about the triphenylamine (TPA; donor) portion of each molecule. Each Dye-X (X=F, Cl, Br, and I) was immobilized on a TiO2 surface to investigate how the halogen substituents affect the reaction between the light-induced charge-separated state, TiO2 (e(-) )/Dye-X(+) , with iodide in solution. Transient absorption spectroscopy showed progressively faster reactivity towards nucleophilic iodide with more polarizable halogen substituents: Dye-F < Dye-Cl < Dye-Br < Dye-I. Given that all other structural and electronic properties for the series are held at parity, with the exception of an increasingly larger electropositive σ-hole on the heavier halogens, the differences in dye regeneration kinetics for Dye-Cl, Dye-Br, and Dye-I are ascribed to the extent of halogen bonding with the nucleophilic solution species.
authors.affiliation: Department of Chemistry, The University of North Carolina at Chapel Hill, Murray Hall 2202B, Chapel Hill, NC, 27599-3290, USA.
authors.forename: Wesley B
authors.initials: WB
authors.lastname: Swords
authors.affiliation: Departments of Chemistry and Chemical & Biological Engineering, The University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T1Z1, Canada.
authors.forename: Sarah J C
authors.initials: SJ
authors.lastname: Simon
authors.affiliation: Departments of Chemistry and Chemical & Biological Engineering, The University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T1Z1, Canada.
authors.forename: Fraser G L
authors.initials: FG
authors.lastname: Parlane
authors.affiliation: Departments of Chemistry and Chemical & Biological Engineering, The University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T1Z1, Canada.
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Dean
authors.affiliation: Departments of Chemistry and Chemical & Biological Engineering, The University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T1Z1, Canada.
authors.forename: Cameron W
authors.initials: CW
authors.lastname: Kellett
authors.affiliation: Department of Chemistry, The University of North Carolina at Chapel Hill, Murray Hall 2202B, Chapel Hill, NC, 27599-3290, USA.
authors.forename: Ke
authors.initials: K
authors.lastname: Hu
authors.affiliation: Department of Chemistry, The University of North Carolina at Chapel Hill, Murray Hall 2202B, Chapel Hill, NC, 27599-3290, USA. gjmeyer@email.unc.edu.
authors.forename: Gerald J
authors.initials: GJ
authors.lastname: Meyer
authors.affiliation: Departments of Chemistry and Chemical & Biological Engineering, The University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T1Z1, Canada. cberling@chem.ubc.ca.
authors.forename: Curtis P
authors.initials: CP
authors.lastname: Berlinguette
keywords: dyes; halogen bonding; inorganic chemistry; reaction kinetics; semiconductor interfaces