Thermally activated polymorphic transition from a 1D ribbon to a 2D carpet: squaric acid on Au(111)

Ueji, Kan; Jung, Jaehoon; Oh, Junepyo; Miyamura, Kazuo; Kim, Yousoo

doi:10.1039/c4cc05794e

Cited by 9 publications

(8 citation statements)

References 23 publications

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“…The latter are related to a remarkable stability of their anions due to electronic π-delocalization [1,2]. As a typical characteristic of neutral oxocarbon molecules [3], strong hydrogen bonds determine the structures of squaric acid both in solid crystals [4] and in adsorbed phases [5]. In recent years, squaric acid and its derivatives have been the object of studies dealing with a variety of properties of these compounds.…”

Section: Introductionmentioning

confidence: 99%

Squaric acid adsorption and oxidation at gold and platinum electrodes

Cheuquepán

Martínez-Olivares

Rodes

et al. 2018

Journal of Electroanalytical Chemistry

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The adsorption and oxidation of squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione, H 2 C 4 O 4 , SQA) at platinum and gold electrodes were studied spectroelectrochemically in perchloric acid solutions. Voltammetric experiments demonstrate that reversible adsorption takes place at gold electrodes in the double-layer region. As a difference with platinum electrodes, no dissociative adsorption processes leading to the blocking of the electrode surface are detected. ATR-SEIRAS experiments show potential-dependent adsorbate bands at potentials below 1.20 V RHE that, according to DFT calculations, can be assigned to adsorbed squarate. For platinum electrodes, the potential-dependent adsorption of squarate anions is coupled with the oxidative stripping of adsorbed carbon monoxide, which is formed upon dissociative SQA adsorption. Bonding of squarate species to the platinum and gold surfaces involves two oxygen atoms in a bidentate configuration, with the molecular plane perpendicular to the metal surface. The ATR-SEIRA spectra obtained for gold electrodes in the SQA oxidation region show bands for adsorbed bicarbonate anions formed from dissolved carbon dioxide molecules. In the case of platinum, distinct bands are observed for adsorbed oxidation products which probably are formed upon opening of the SQA ring.

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Section: Introductionmentioning

confidence: 99%

Squaric acid adsorption and oxidation at gold and platinum electrodes

Cheuquepán

Martínez-Olivares

Rodes

et al. 2018

Journal of Electroanalytical Chemistry

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“…11−23 Examples for molecular polymorphism at the solid/vacuum interface include self-assembled monolayers, 24,25 halogenated polyphenylenes, 26−29 porphyrins, 30 subphthalocyanines, 31 amino acids such as alanine, 32 and squaric acid. 33 Arene dicarbonitriles constitute a class of organic molecules that are well-studied with respect to their adsorbate structures on metal single-crystal surfaces. This holds especially for the linear oligophenylene para-dicarbonitriles (Figure 1a), which show pronounced size and substrate dependence of their (sub)monolayer structures.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Structure formation at metal/organic interfaces is another area where polymorphism comes into play. The electronic properties of organic semiconductors and their interfaces with metals in organic (opto)electronic devices also vary between different polymorphs. , Especially important is the structure of the first adsorbed layer, which determines the interface properties and can also control the structure of further molecular layers during deposition. , Related previous work was mainly performed at the solid/liquid interface, where the solvent was shown to strongly influence the interface structure. − Examples for molecular polymorphism at the solid/vacuum interface include self-assembled monolayers, , halogenated polyphenylenes, − porphyrins, subphthalocyanines, amino acids such as alanine, and squaric acid …”

Section: Introductionmentioning

confidence: 99%

Polymorphism at the Metal/Organic Interface: Hybrid Phase with Alternating Coplanar and Vertical Adsorption Geometry

et al. 2020

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Polymorphism of organic molecular materials plays a prominent role in organic (opto)electronic devices, where the structural properties of metal/organic interfaces determine performance-critical parameters such as charge carrier injection rates. Here, we show that (sub)monolayers of a 2D-prochiral aromatic dinitrile with a bent quaterphenyl backbone engage in pronounced polymorphism on a Ag(111) surface and form a unique phase with alternating polar orientation of the molecules. In the saturated monolayer, the molecules are nearly coplanar with the substrate (flat-lying) and form an ordered racemic structure consisting of chiral dimers stabilized by H···NC hydrogen bonds. At submonolayer coverages, two ordered phases coexist with a dilute mobile phase. One phase forms homochiral domains with a quasi-Kagome structure. The other phase has a unique structure consisting of alternating rows of flat-lying and upright-standing molecules. The two different polar orientations can be distinguished by scanning tunneling microscopy. The upright-standing molecules have a straight and brighter shape and show increased packing density compared to their flat-lying counterparts. These results reveal the great local variability of molecular arrangements at metal/organic interfaces, even for fixed global parameters such as temperature and coverage.

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“…4−11 However, surface-confined molecular assemblies can exhibit an energetic equivalence of different structures, leading to polymorphism, that is, the simultaneous presence of different isoenergetic arrangements for the same compound. Transitions between those arrangements can be promoted, inter alia, by altering the number of substituents for the molecular compound, 12 adsorbing the same compound on a different substrate, 13,14 providing energy by means of annealing of the sample, 15,16 varying the molecular coverage, 17−20 or a combination of these factors. 21−23…”

Section: Introductionmentioning

confidence: 99%

Coverage-Controlled Polymorphism of H-Bonded Networks on Au(111)

Schmidt¹,

Enache²,

Maggini

et al. 2019

J. Phys. Chem. C

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We report on the self-assembly of a conformational flexible organic compound on Au(111) using scanning tunneling microscopy and low-energy electron diffraction measurements. We observed different conformers of the compound upon adsorption on the reconstructed Au(111) surface. Increasing the molecular coverage enhanced the lateral pressure, that is, parallel to the surface, favoring a coverage-controlled transition from a supramolecular network displaying only one molecular organization, into a polymorphic array with two coexisting arrangements. Our results give insights into the role of substrate-induced conformational changes on the formation of polymorphic supramolecular networks.

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Thermally activated polymorphic transition from a 1D ribbon to a 2D carpet: squaric acid on Au(111)

Cited by 9 publications

References 23 publications

Squaric acid adsorption and oxidation at gold and platinum electrodes

Squaric acid adsorption and oxidation at gold and platinum electrodes

Polymorphism at the Metal/Organic Interface: Hybrid Phase with Alternating Coplanar and Vertical Adsorption Geometry

Coverage-Controlled Polymorphism of H-Bonded Networks on Au(111)

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