Chemically Powered Micro‐ and Nanomotors

Chemically powered micro‐ and nanomotors are small devices that are self‐propelled by catalytic reactions in fluids. Taking inspiration from biomotors, scientists are aiming to find the best architecture for self‐propulsion, understand the mechanisms of motion, and develop accurate control over the motion. Remotely guided nanomotors can transport cargo to desired targets, drill into biomaterials, sense their environment, mix or pump fluids, and clean polluted water. This Review summarizes the major advances in the growing field of catalytic nanomotors, which started ten years ago.     

Multiscale Approach to the Study of the Electronic Properties of Two Thiophene Curcuminoid Molecules

We studied the electronic and conductance properties of two thiophene–curcuminoid molecules, 2‐thphCCM ( 1 ) and 3‐thphCCM ( 2 ), in which the only structural difference is the position of the sulfur atoms in the thiophene terminal groups. We used electrochemical techniques as well as UV/Vis absorption studies to obtain the values of the HOMO–LUMO band gap energies, showing that molecule 1 has lower values than 2 . Theoretical calculations show the same trend. Self‐assembled monolayers (SAMs) of these molecules were studied by using electrochemistry, showing that the interaction with gold reduces drastically the HOMO–LUMO gap in both molecules to almost the same value. Single‐molecule conductance measurements show that molecule 2 has two different conductance values, whereas molecule 1 exhibits only one. Based on theoretical calculations, we conclude that the lowest conductance value, similar in both molecules, corresponds to a van der Waals interaction between the thiophene ring and the electrodes. The one order of magnitude higher conductance value for molecule 2 corresponds to a coordinate (dative covalent) interaction between the sulfur atoms and the gold electrodes.     

Cyclopalladation and Reactivity of Amino Esters through C?H Bond Activation: Experimental,Kinetic, and Density Functional Theory Mechanistic Studies

The orthopalladation, through C? H bond activation, of a large number of amino esters and amino phosphonates derived from phenylglycine, and having different substituents at the aryl ring and the C‐α atom, as well as on the N‐amine atom, has been studied. The experimental observations indicated an improvement in the yields of the orthopalladated compounds when the N‐amine and/or the C‐α atom are substituted, when compared with the unsubstituted methyl phenylglycinate derivatives. In contrast, substitutions at the aryl ring do not promote significant changes in the orthometalation results. Furthermore, the use of hydrochloride salts of the amino esters has also been shown to have a remarkably favorable effect on the process. All these observations have been fully quantified at different temperatures and pressures by a detailed kinetic study in solution in different solvents and in the presence and absence of added Brønsted acids and chloride anions. The data collected indicate relevant changes in the process depending on these conditions, as expected from the general background known for cyclopalladation reactions. An electronic mechanism of the orthopalladation has been proposed based on DFT calculations at the B3LYP level, and a very good agreement between the trends kinetically measured and the theoretically calculated activation barriers has been obtained. The reactivity of the new orthopalladated amino phosphonate derivatives has been tested and it was found that their halogenation, alkoxylation and carbonylation resulted in formation of the corresponding functionalized ortho‐haloaminophosphonates, ortho‐alkoxyaminophosphonates and oxoisoindolinylphosphonates.     

A transformation for the mixed general routing problem with turn penalties

In this paper, we study a generalization of the Mixed General Routing Problem (MGRP) with turn penalties and forbidden turns. Thus, we present a unified model of this kind of extended versions for both node- and arc-routing problems with a single vehicle. We provide a polynomial transformation of this generalization into an asymmetric travelling salesman problem, which can be considered a particular case of the MGRP. We show computational results on the exact resolution on a set of 128 instances of the new problem using a recently developed code for the MGRP.     

On the 𝔉‐hypercentre of a finite group

The main objective of this paper is to study and describe the hypercentre of a finite group associated with saturated formations, in terms of some subgroup embedding properties related to permutability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Quantum mechanics: cleaning up metaphysical baggage

The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e, 2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties obtained by this method for different types of molecules are discussed.     

Elaboration of ZnO Thin Films with Preferential Orientation by a Soft Chemistry Route

Microcrystalline ZnO films presenting well-defined and tunable orientation were obtained by spin coating of alcoholic sols by two different approaches, based on controlled hydrolysis-condensation of Zn-ethanolamine complexes. As-deposited films are formed by amorphous zinc oxide-acetate submicronic particles, which are transformed into oriented ZnO after thermal treatment. The orientation of ZnO depends on the synthesis method, and the solvent. While in ethanol and [Zn] = 0.05 mol·L^–1, films consist of rectangular platelets oriented with the (100) planes parallel to the substrate (a//n), the orientation of the particles changes to (c//n) for systems in 2-methoxyethanol (2-ME) and [Zn] = 0.75 mol·L^–1. A study of chemical factors that influence the orientation (precursor, solvent, MEA/Zn ratio, concentration, coating parameters, heat treatment) is presented.