Ubiquitous deprotonation of terephthalic acid in the self-assembled phases on Cu(100)

Abstract

We performed an exhaustive study of terephthalic acid (TPA) self-assembly on a Cu(100) surface, where first-layer molecules display two sequential phase transitions in the 200-400 K temperature range, corresponding to different stages of molecular deprotonation. We followed the chemical and structural changes by means of high-resolution X-ray photoelectron spectroscopy (XPS) and variable-temperature scanning tunneling microscopy (STM), which were interpreted on the basis of density functional theory (DFT) calculations and photoemission simulations. In order to reveal the spectroscopic contributions of the molecules in different states of deprotonation, we modified the substrate reactivity by deposition of a small amount of Sn, which hampers the deprotonation reaction. We found that the characteristic molecular ribbons of the TPA/Cu(100) α-phase at a low temperature contain a significant fraction of partially deprotonated molecules, in contrast to the expectation of a fully protonated phase, where the self-assembly was claimed to be simply driven by the intermolecular double hydrogen bonds [OHO]. On the basis of our simulations, we propose a model where the carboxylate groups of the partially deprotonated molecules form single hydrogen bonds with the carboxylic groups of the fully protonated molecules. Using real time XPS, we also monitored the kinetics of the deprotonation reaction. We show that the network of mixed single and double hydrogen bonds inhibits further deprotonation up to ∼270 K, whereas the isolated molecules display a much lower deprotonation barrier.

Multiscale Analysis of Phase Transformations in Self-Assembled Layers of 4,4′-Biphenyl Dicarboxylic Acid on the Ag(001) Surface

“…The O 1s spectrum of the β phase shows three peak components, associated with hydroxyl (magenta), carbonyl (blue), and carboxylate (orange) oxygens, respectively. Their shifts with respect to the α and fully deprotonated phase are in agreement with our DFT calculations and those reported for TPA/Cu. , Since the intensity ( i . e ., the area under the peak) of the carboxylate peak is twice the intensity of both hydroxyl and carbonyl peaks, we obtain a (hydroxyl + carbonyl):carboxylate intensity ratio of (1 + 1):2, which agrees with the 1:1 ratio of functional groups.…”

“…Their shifts with respect to the α and fully deprotonated phase are in agreement with our DFT calculations and those reported for TPA/ Cu. 28,29 Since the intensity (i.e., the area under the peak) of the carboxylate peak is twice the intensity of both hydroxyl and carbonyl peaks, we obtain a (hydroxyl + carbonyl):carboxylate intensity ratio of (1 + 1):2, which agrees with the 1:1 ratio of functional groups. However, this ratio is not expressed at the molecular level.…”

Snapshots of Dynamic Adaptation: Two‐Dimensional Molecular Architectonics with Linear Bis‐Hydroxamic Acid Modules

“…The amino group does not seem to direct the assembly. We note that more recent reports on the self‐assembly of dicarboxylic‐acid‐containing molecules indicate that the corresponding overlayer unit cell can also be expressed after (partial) dissociation of the O−H bond, an event which cannot be excluded based on our XPS data, especially on the Ag(111) surface.…”

Modeling the Dimeric Structure of Partly Deprotonated Trimesic Acid Molecules

“…One of them is intelligent design of versatile building blocks, aromatic carboxylic acids in particular, for development of self-assembled layers with the desired nanostructure and properties. , A lot of recent studies have been also focused on the effect of external stimuli in directing the self-organization of organic molecules into planar two-dimensional (2D) structures . Thermal annealing and electric pulse or bias voltage have been shown to trigger the deprotonation of carboxyl groups in hydrogen-bonded (H-bonded) networks of trimesic acid (TMA), 1,3,5-benzene-tribenzoic acid (BTB), and other small molecules. , In some cases, deprotonation leads to simple decomposition of the ordered monolayers, while in other cases, monolayers undergo a transition to completely different ordered structures due to the formation of strong ionic H-bonds between the carboxylate anions and neutral carboxyl groups.…”

“…3 Thermal annealing and electric pulse or bias voltage have been shown to trigger the deprotonation of carboxyl groups in hydrogen-bonded (H-bonded) networks of trimesic acid (TMA), 4 1,3,5-benzene-tribenzoic acid (BTB), 5 and other small molecules. 6,7 In some cases, deprotonation leads to simple decomposition of the ordered monolayers, while in other cases, monolayers undergo a transition to completely different ordered structures due to the formation of strong ionic H-bonds between the carboxylate anions and neutral carboxyl groups.…”