title: Self-Assembled Monolayers of Pseudo-C2v-Symmetric, Low-Band-Gap Areneoxazolethiolates on Gold Surfaces.
abstract: A series of three homologous arene[2,3-d]-oxazole-2-thiols (benzoxazole-2-thiol (BOxSH), naphthaleneoxazole-2-thiol (NOxSH), and anthraceneoxazole-2-thiol (AOxSH)) were deposited onto Au(111) to obtain surfaces suitable as injection layers for organic electronics. The guiding idea was that the increasingly extended conjugated system would lower the band gap of the films while the introduction of the annulated heteroaromatic ring would provide the opportunity for pseudosymmetric attachment of the sulfur anchor, what should lower the conformational freedom of the system. In fact, the annulation of the oxazole ring lowers the optical band gaps of the parent compounds to 3.1-4.0 eV, depending on the number of benzene rings. To characterize the respective monolayers, a variety of spectroscopic techniques such as ellipsometry, infrared reflection-absorption spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy have been utilized. The monolayers of BOxS exhibit a lower film quality than those of NOxS and AOxS, with enhanced molecular density and more upright molecular orientation with increasing molecular length. Infrared spectroscopy suggests that the nitrogen atoms of the oxazole rings are located more closely to the Au(111) surface than the oxygen atoms, although no hints for an electronic interaction between the N atoms and the gold surface could be found. This preferred orientation could be tentatively traced to packing effects, solving a conundrum of the literature.
authors.affiliation: Institute of Inorganic and Analytical Chemistry, Frankfurt University , Max-von-Laue-Straße 7, 60438 Frankfurt, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Partes
authors.affiliation: Applied Physical Chemistry, Heidelberg University , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
authors.forename: Can
authors.initials: C
authors.lastname: Yildirim
authors.affiliation: Applied Physical Chemistry, Heidelberg University , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
authors.forename: Swen
authors.initials: S
authors.lastname: Schuster
authors.affiliation: Institute of Inorganic and Analytical Chemistry, Frankfurt University , Max-von-Laue-Straße 7, 60438 Frankfurt, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Kind
authors.affiliation: Institute of Organic Chemistry and Chemical Biology, Frankfurt University , Max-von-Laue-Straße 7, 60438 Frankfurt, Germany.
authors.forename: Jan W
authors.initials: JW
authors.lastname: Bats
authors.affiliation: Applied Physical Chemistry, Heidelberg University , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Zharnikov
authors.affiliation: Institute of Inorganic and Analytical Chemistry, Frankfurt University , Max-von-Laue-Straße 7, 60438 Frankfurt, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Terfort