For entropic reasons, the synthesis of macrocycles via olefin ring-closing metathesis (RCM) is impeded by competing acyclic diene metathesis (ADMET) oligomerization. With cationic molybdenum imido alkylidene N-heterocyclic carbene (NHC) complexes confined in tailored ordered mesoporous silica, RCM can be run with macrocyclization selectivities up to 98% and high substrate concentrations up to 0.1 M. Molecular dynamics simulations show that the high conversions are a direct result of the proximity between the surface-bound catalyst, proven by extended X-ray absorption spectroscopy, and the surface-located substrates. Back-diffusion of the macrocycles decreases with decreasing pore diameter of the silica and is responsible for the high macrocyclization efficiency. Also, Z-selectivity increases with decreasing pore diameter and increasing Tolman electronic parameter of the NHC. Running reactions at different concentrations allows for identifying the optimum substrate concentration for each material and substrate combination.

A critical requirement for the application of organic thin-film transistors (TFTs) in mobile or wearable applications is low-voltage operation, which can be achieved by employing ultrathin, high-capacitance gate dielectrics. One option is a hybrid dielectric composed of a thin film of aluminum oxide and a molecular self-assembled monolayer in which the aluminum oxide is formed by exposure of the surface of the aluminum gate electrode to a radio-frequency-generated oxygen plasma. This work investigates how the properties of such dielectrics are affected by the plasma power and the duration of the plasma exposure. For various combinations of plasma power and duration, the thickness and the capacitance of the dielectrics, the leakage-current density through the dielectrics, and the current–voltage characteristics of organic TFTs in which these dielectrics serve as the gate insulator have been evaluated. The influence of the plasma parameters on the surface properties of the dielectrics, the thin-film morphology of the vacuum-deposited organic-semiconductor films, and the resulting TFT characteristics has also been investigated.

Atom Probe Tomography (APT) is currently a well-established technique to analyse the composition of solid materials including metals, semiconductors and ceramics with up to near-atomic resolution. Using an aqueous glucose solution, we now extended the technique to frozen solutions. While the mass signals of the common glucose fragments CxHy and CxOyHz overlap with (H2O)nH from water, we achieved stoichiometrically correct values via signal deconvolution. Density functional theory (DFT) calculations were performed to investigate the stability of the detected pyranose fragments. This paper demonstrates APT’s capabilities to achieve sub-nanometre resolution in tracing whole glucose molecules in a frozen solution by using cryogenic workflows. We use a solution of defined concentration to investigate the chemical resolution capabilities as a step toward the measurement of biological molecules. Due to the evaporation of nearly intact glucose molecules, their position within the measured 3D volume of the solution can be determined with sub-nanometre resolution. Our analyses take analytical techniques to a new level, since chemical characterization methods for cryogenically-frozen solutions or biological materials are limited.

Atom probe tomography allows us to measure the three-dimensional composition of materials with up to atomic resolution by evaporating the material using high electric fields. Initially developed for metals, it is increasingly used for covalently bound structures. To aid the interpretation of the obtained fragmentation pattern, we modeled the fragmentation and desorption of self-assembled monolayers of thiolate molecules on a gold surface in strong electrostatic fields using density functional theory. We used a cluster model and a periodic model of amino-undecanethiolate, NH 2 (CH 2 ) 11 S, and fluoro-decanethiolate, CF 3 (CF 2 ) 7 (CH 2 ) 2 S. In the former molecule, the fragment CH 2 NH 2 + was found to evaporate at fields of 5.4−7.7 V/nm. It was followed by different hydrocarbon fragments. Fluorodecanethiolate evaporates CF 3 + at fields of 5.7−6.7 V/nm in the cluster model and at 15.4−23.1 V/nm in the periodic model, followed by CF 2 + and C 2 F 4 2+ . Detailed analysis of the electronic structure during the evaporation process revealed a stepwise accumulation of the charge in the head groups exposed to the strongest fields, followed by dissociation of covalent bonds. These observations will facilitate the analysis of atom probe experiments of covalently bound structures.

Mesoporous catalyst supports that mimic the spatially confined active sites of enzymes can aid in the development of highly selective molecular heterogeneous catalysts. Nontemplated mesoporous SiO 2 (NT-mSiO 2 ) materials with open porosity, tunable pore sizes, and high diffusivity are promising candidates in this regard. However, the operationalization of such materials strongly depends on the controlled passivation of their external pore surfaces. This enables catalyst molecules to be selectively immobilized on the internal pore surface where the desired spatial confinement effects can be observed. In this work, confocal laser scanning microscopy (CLSM) is presented as a viable analytical tool to visualize the passivation efficiency and permeability of NT-mSiO 2 platelets consisting of interconnected mesopores (d pore = 9.4 nm) with positive pore wall curvatures. CLSM investigations with representative fluorescent probe molecules show that after pore-filling with Pluronic P123, the passivating film is constrained to the external platelet surface. The permeability of different passivating films based on mono and bifunctional silanes is compared. A pyrene-based organosilane is used as a tracer molecule to determine the covalent functionalization susceptibility of passivated NT-mSiO 2 platelets. Additionally, SiO 2 nanospheres with modular particle sizes are synthesized using an L-lysine-mediated sol−gel process and assembled into NT-mSiO 2 with tunable pore sizes. Hexamethyldisilazane-passivated NT-mSiO 2 (d pore = 4.3 nm) is used as a catalyst support for the immobilization of cationic molybdenum imido alkylidene N-heterocyclic carbene complexes to study the effect of confinement on monomacrocyclization selectivity in ring-closing olefin metathesis reactions. A 31% enhancement in monomacrocyclization selectivity is observed when compared to the homogeneous catalyst.