We have prepared self-assembled monolayers (SAMs) of 4-aminothiophenol (4-ATP) and 1-(4-mercaptophenyl)-2,6-diphenyl-4-(4-pyridyl)pyridinium tetrafluoroborate (MDPP) functionalized with iron phthalocyanine (FePc) and copper phthalocyanine (CuPc) adsorbed on gold (111) electrodes. The catalytic activity of these SAMs/MPc was examined for the reduction of O 2 in aqueous solutions and compared to that of bare gold and with gold coated directly with preadsorbed MPc molecules. Scanning tunneling microscopy (STM) studies confirm the functionalization of the 4-ATP by MPc. STM images reveal that iron phthalocyanine molecules are chemically anchored to 4-aminothiophenol organic monolayers, probably having an "umbrella" type orientation with regards to the surface. The electrocatalytic studies carried out with Au/4-ATP/FePc and Au/ MDPP/FePc electrodes show that the O 2 reduction takes place by the transfer of 4-electron to give water in contrast to a 2-electron transfer process observed for the bare gold. The modified electrode obtained by simple adsorption of FePc directly to the Au(111) surface still promotes the 4-electron reduction process, but it shows a lower activity than the electrodes involving SAMs with FePc molecules positioned at the outmost portion of the selfassembled monolayers. The activity of the electrodes increases as follow: Au < Au/FePc < Au/4-ATP/FePc < Au/MDPP/FePc with the highest activity when FePc molecules are more separated from the Au surface. In contrast, the less active CuPc shows almost the same activity in all three configurations. Theoretical calculations suggest the importance of the back-bonding into the adduct formation, showing the relevance of the supporting gold surface on the electron-transfer process mediated by anchoring ligands.

The formation of self-assembly monolayers (SAMs) based on a gold substrate and a thiolate ligand as "anchor" fragment of metallophtalocyanine has been employed as strategy toward the obtention of modified electrodes. In this Article, the formation of SAM's involving iron and cobalt phtalocyanines anchored by 4-aminothiophenol (4-ATP) and 4-mercatopyridine (4-MP) to the Au(111) surface is explored by both experimental and theoretical studies for a better understanding of their bonding pattern and optical properties. The self-assembly metallophthalocyanines complexes on gold electrode exhibits an interesting charge donation from the 4-ATP or 4-MP toward both gold substrate and phtalocyanine, denoting an effective goldÀMPc interaction mediated by the titled anchor ligands. In addition, the optical properties of the self-assembled complexes supported on the gold electrode exhibit in conjuction with the well-described Q-band an interesting charge transfer from the Pc (π) toward the gold surface, as could be observed in the FePc-4MP-Au 26 assembly.

Complexity is a concept that is being considered in chemistry as it has shown potential to reveal interesting phenomena. Thus, it is possible to study chemical phenomena in a new approach called systems chemistry. The systems chemistry has an organization and function, which are regulated by the interactions among its components. At the simplest level, noncovalent interactions between molecules can lead to the emergence of large structures. Consequently, it is possible to go from the molecular to the supramolecular systems chemistry, which aims to develop chemical systems highly complex through intra-and intermolecular forces. Proper use of the interactions previously mentioned allow a glimpse of supramolecular system chemistry in many tasks such as structural properties reflecting certain behaviors in the chemistry of materials, for example, electrical and optical, processes of molecular recognition and among others. In the last time, within this area, inorganic supramolecular systems chemistry has been developed. Those systems have a structural orientation which is defined by certain forces that predominate in the associations among molecules. It is possible to recognize these forces as hydrogen bonding, π-π stacking, halogen bonding, electrostatic, hydrophobic, charge transfer, metal coordination, and metallophilic interactions. The presence of these forces in supramolecular system yields certain properties such as light absorption and luminescence. The quantum theoretical modeling plays an important role in the designing of the supramolecular system. The goal is to apply supramolecular principles in order to understand the associated forces in many inorganic molecules that include heavy metals for instance gold, platinum, and mercury. Relevant systems will be studied in detail, considering functional aspects such as enhanced coordination of functionalized molecular self-assembly, electronic and optoelectronic properties. K E Y W O R D Sdensity functional theory, dispersion term, Post-Hartree-Fock, van der Waals forces Grimme´s dispersion (D3)

The interaction of thiol and thiolate containing molecules with gold (S-Au) has gained increasing interest because of its applications in molecular electronic devices and catalysis. In this context, the enhanced conductivity of thiophenol compared to alkanethiol represents an opportunity to develop more sensitive and selective gold-based devices by incorporating molecules with the aryl-thiol moiety into their structures. As has been proposed earlier, the thiol moiety is deprotonated after binding to gold, hence, we present here a comparative study of the S-Au bond strength between several neutral and deprotonated aromatic-sulfur systems in their anionic and radical forms with a detailed description of the nature of this interaction. The study was performed by means of computational chemistry methods, using a cluster of 42 Au atoms as a model of the Au(111) surface that allowed us to provide new chemical insights to control the S-Au interface interaction strength. Our results revealed that the thiophenols-gold interaction is mainly dispersive where the interaction energies range between 31 and 43 kcal mol(-1). The radical and anionic thiophenolates-gold interaction increases due to a strong charge transfer character, depicting interaction energies in the range of 50 to 55 kcal mol(-1) and 62 to 92 kcal mol(-1), respectively. These results suggest that for the anionic thiophenolate the binding strength can be tailored according to the electron-donor capabilities of the ligand which in turn can be finely tuned by several substituents. Our results are of possible impact for the design of new devices.

Artículo de publicación ISISin acceso a texto completoIt is widely known that sulfur ligands, such as alkanethiols or phenothiols and their derivatives, are useful anchor systems for gold materials due to the high affinity of sulfur to gold surfaces. In this study we use DFT calculations and a 42-atom gold cluster model to study the interaction between selenophenol and tellurophenol-derivatives with the Au(111) surface to gain information towards potential new gold-based materials. We modulated the interaction strength by controlling the charge transfer process of a particular interaction by chemically modifying the ligands. To obtain a complete analysis, we studied the ligands in their protonated, anionic and radical states aiming to cover the three possibilities in which these may interact with the gold cluster. In order to get a deeper insight into the nature of the interaction we used several analysis techniques such as energy decomposition analysis (EDA), non-covalent interactions (NCI) and natural population analysis (NPA). Our results reveal that tellurium in the anionic state provides complexes of better thermodynamic stability by similar to 12.0 kcal mol, when compared with the strongest sulfur-gold complex, also in the anionic state. Furthermore, this indicates that the anionic ligand is probably the dominant state for both selenium and tellurium as observed previously for sulfur. The extent to which the interaction strength could be controlled directly depends on the state of the anchor atom. In our case the anionic state is the most suitable for tuning the interaction. Finally, our main findings suggest that exchanging sulfur with selenium or tellurium involves an important increase of the interaction strength, thus, making these selenophenol and tellurophenol derivatives attractive for the development of new functional materials.FONDECYT 3130383 1140503 1150629 Grant ICM 120082 CONICYT 21130874 German Research Foundation (DFG) EXC 310/