title: Coverage-Dependent Anchoring of 4,4'-Biphenyl Dicarboxylic Acid to CoO(111) Thin Films.
abstract: We investigated the adsorption behavior of 4,4'-biphenhyl dicarboxylic acid (BDA) on well-ordered CoO(111) films grown on Ir(100) as a function of coverage and temperature using time-resolved and temperature-programmed infrared reflection absorption spectroscopy (TR-IRAS, TP-IRAS) in combination with density functional theory (DFT) and scanning tunneling microscopy (STM) under ultrahigh vacuum (UHV) conditions. To compare the binding behavior of BDA as a function of the oxide film thickness, three different CoO(111) film thicknesses were explored: films of about 20 bilayers (BLs) (approximately 5 nm), 2 BLs, and 1 BL. The two carboxylic acid groups of BDA offer two potential anchoring points to the oxide surface. At 150 K, intact BDA adsorbs on 20 BL thick oxide films in planar geometry with the phenyl rings aligned parallel to the surface. With decreasing oxide film thickness, we observe an increasing tendency for deprotonation and the formation of flat-lying BDA molecules anchored as dicarboxylates. After saturation of the first monolayer, intact BDA multilayers grow with molecules aligned parallel to the surface. The BDA multilayer desorbs at around 360 K. Completely different growth behavior is observed if BDA is deposited above the multilayer desorption temperature. Initially, doubly deprotonated dicarboxylates are formed by adopting a flat-lying orientation. With increasing exposure, however, the adsorbate layer transforms into upright standing monocarboxylates. A sharp OH stretching band (3584 cm-1) and a blue-shifted CO stretching band (1759 cm-1) indicate weakly interacting apical carboxylic acid groups at the vacuum interface. The anchored monocarboxylate phase slowly desorbs in a temperature range of up to 470 K. At higher temperature, a flat-lying doubly deprotonated BDA is formed, which desorbs and decomposes in a temperature range of up to 600 K.
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Susanne
authors.identifier: 0000-0001-6735-4477
authors.initials: S
authors.lastname: Mohr
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Schmitt
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Tibor
authors.initials: T
authors.lastname: Döpper
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Feifei
authors.initials: F
authors.lastname: Xiang
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Schwarz
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Görling
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: M Alexander
authors.identifier: 0000-0002-8607-3301
authors.initials: MA
authors.lastname: Schneider
authors.affiliation: Lehrstuhl für Physikalische Chemie II, ‡Lehrstuhl für Festkörperphysik, §Lehrstuhl für Theoretische Chemie, and ∥Erlangen Catalysis Resource Center and Interdisciplinary Center Interface-Controlled Processes, Friedrich-Alexander-Universität Erlangen-Nürnberg , 91058 Erlangen, Germany.
authors.forename: Jörg
authors.initials: J
authors.lastname: Libuda