Redox-Active Catechol-Functionalized Molecular Rods: Suitable Protection Groups and Single-Molecule Transport Investigations

Hollow Ru/RuO2 nanospheres with nanoparticulate shells for high performance electrocatalytic oxygen evolution reactions

This work shows that hollow Ru/RuO2 nanoparticles having nanoparticulate shells (HN-Ru/RuO2) can be prepared using hollow microporous organic polymers with Ru species (H-MOP-Ru) as precursors. Using silica spheres as templates, H-MOPs were prepared through the Sonogashira-Hagihara coupling of 1,3,5-triethynylbenzene with 2,3-ethoxymethylenedioxy-1,4-diiodobenzene. Acid hydrolysis of cyclic ethyl orthoformate protecting groups generated catechol moieties to form H-MOP-Cat. Then, H-MOP-Ru was obtained by incorporating Ru species into H-MOP-Cat. Heat-treatment of H-MOP-Ru under air induced the formation of HN-Ru/RuO2 with a diameter of 61 nm and shells consisting of 6-7 nm nanoparticles. Due to the hollow structure and nanoparticulate shells, HN-Ru/RuO2 showed a high surface area of 80 m2 g-1 and a pore volume of 0.18 cm3 g-1. The HN-Ru/RuO2 showed enhanced electrocatalytic performance for the oxygen evolution reaction (OER) with an overpotential of 295 mV @ 10 mA cm-2 and a Tafel slope of 46 mV dec-1 in alkaline electrolyte, compared with control RuO2 such as commercial Ru/RuO2 nanoparticles (A-Ru/RuO2) and home-made Ru/RuO2 nanoparticles (N-Ru/RuO2) prepared via the same synthetic procedure as HN-Ru/RuO2. While HN-Ru/RuO2 inevitably contained Pd originated from coupling catalysts, it showed superior performance to Ru/RuO2 nanoparticles with the same Pd content (N1-Ru/RuO2), indicating that the efficient electrocatalytic performance of HN-Ru/RuO2 is attributable to its hollow structure and nanoparticulate shells.

Design and Synthesis of Bio-Inspired Polyurethane Films with High Performance

In the present work, the synthesis of segmented polyurethanes functionalized with catechol moieties within the hard or the soft segment is presented. For this purpose, a synthetic route of a new catechol diol was designed. The direct insertion of this catechol-free derivative into the rigid phase led to segmented polyurethanes with low performance (σmax ≈ 4.5 MPa). Nevertheless, when the derivative was formally located within the soft segment, the mechanical properties of the corresponding functionalized polyurethane improved considerably (σmax ≈ 16.3 MPa), owing to a significant increase in the degree of polymerization. It is proposed that this difference in reactivity could probably be attributed to a hampering effect of this catecholic ring during the polyaddition reaction. To corroborate this hypothesis, a protection of the aromatic ring was carried out, blocking the hampering effect and avoiding secondary reactions. The polyurethane bearing the protected catechol showed the highest molecular weight and the highest stress at break described to date (σmax ≈ 66.1 MPa) for these kind of catechol-functionalized polyurethanes. Therefore, this new approach allows for the obtention of high-performance polyurethane films and can be applied in different sectors, benefiting from the molecular adhesion introduced by the catechol ring.

Nanofabrication Techniques in Large-Area Molecular Electronic Devices

The societal impact of the electronics industry is enormous—not to mention how this industry impinges on the global economy. The foreseen limits of the current technology—technical, economic, and sustainability issues—open the door to the search for successor technologies. In this context, molecular electronics has emerged as a promising candidate that, at least in the short-term, will not likely replace our silicon-based electronics, but improve its performance through a nascent hybrid technology. Such technology will take advantage of both the small dimensions of the molecules and new functionalities resulting from the quantum effects that govern the properties at the molecular scale. An optimization of interface engineering and integration of molecules to form densely integrated individually addressable arrays of molecules are two crucial aspects in the molecular electronics field. These challenges should be met to establish the bridge between organic functional materials and hard electronics required for the incorporation of such hybrid technology in the market. In this review, the most advanced methods for fabricating large-area molecular electronic devices are presented, highlighting their advantages and limitations. Special emphasis is focused on bottom-up methodologies for the fabrication of well-ordered and tightly-packed monolayers onto the bottom electrode, followed by a description of the top-contact deposition methods so far used.

Low variability of single-molecule conductance assisted by bulky metal–molecule contacts

A detailed study of the trimethylsilylethynyl moiety, –CCSiMe₃ (TMSE), as an anchoring group, using a combination of experiment and DFT is presented.

Mild Ti-mediated transformation of t-butyl thio-ethers into thio-acetates

We report a straightforward method for the rapid conversion of thio-ethers to thio-acetates using TiCl4, in good to excellent yields. The reaction conditions tolerate a variety of functional groups, including halide, nitro, ether, thiophene and acetylene functionalities. A catalytic variant of this reaction is also described.

A novel cell-permeable, selective, and noncompetitive inhibitor of KAT3 histone acetyltransferases from a combined molecular pruning/classical isosterism approach

Selective inhibitors of the two paralogue KAT3 acetyltransferases (CBP and p300) may serve not only as precious chemical tools to investigate the role of these enzymes in physiopathological mechanisms but also as lead structures for the development of further antitumor agents. After the application of a molecular pruning approach to the hardly optimizable and not very cell-permeable garcinol core structure, we prepared many analogues that were screened for their inhibitory effects using biochemical and biophysical (SPR) assays. Further optimization led to the discovery of the benzylidenebarbituric acid derivative 7h (EML425) as a potent and selective reversible inhibitor of CBP/p300, noncompetitive versus both acetyl-CoA and a histone H3 peptide, and endowed with good cell permeability. Furthermore, in human leukemia U937 cells, it induced a marked and time-dependent reduction in the acetylation of lysine H4K5 and H3K9, a marked arrest in the G0/G1 phase and a significant increase in the hypodiploid nuclei percentage.

The impact of E-Z photo-isomerization on single molecular conductance

The single molecule conductance of the E and Z isomers of 4,4'-(ethene-1,2-diyl)dibenzoic acid has been determined using two scanning tunneling microscopy (STM) methods for forming molecular break junctions [the I(s) (I = current and s is distance) method and the in situ break junction technique]. Isomerization leads to significant changes in the electrical conductance of these molecules, with the Z isomer exhibiting a higher conductance than the E isomer. Isomerization is achieved directly on the gold surface through photoirradiation, and the STM is used to determine conductance before and after irradiation; reversible switching between the two isomers could be achieved through irradiation of the surface bound species at different wavelengths. In addition, three groups of molecular conductance values [A ("low"), B ("medium"), and C ("high")] have been measured for these carboxylate-terminated molecules. The origin of these conductance groups as well as the increase of the conductance for the Z isomer have been analyzed by comparing the length of the molecules extended in the gap, derived from molecular modeling, with the experimentally observed break-off distance for both isomers.