Optical and Electrochemical Properties of a Photosensitive Pyromellitic Diimide Derivative of Cymantrene.

Photochemical properties of symmetrical pyromellitic diimide containing two cymantrenyl fragments at two nitrogen atoms were studied with IR, NMR, UV-vis, ESI-MS, and cyclic voltammetry. It was found that new unstable chelates are formed during photolysis. At the same time, the CO ligand dissociates from two Mn(CO)3 fragments during photoexcitation, which dramatically changes the electronic and redox properties of the molecule compared to the cymantrene derivative containing one imide fragment. Photolysis leads to a color change from light yellow to green. DFT calculations confirmed the possibility of the formation of complexes due to the loss of one or two CO ligands from manganese atoms. The results obtained with variation of photolysis conditions demonstrated the hemilabile character of the Mn-O=C(imide) bond. On addition of external ligands, the color and electrochemical properties changed, which is promising for the use of this complex as a sensor for small molecules.

A statistical design approach to the sol-gel synthesis of (amino)organosilane hybrid nanoparticles.

This study comprehensively investigates the efficiency of the formulation of tetraethoxysilane (TEOS) and 3-aminopropyltriethoxysilane (APTES) copolymer in sol-gel syntheses as part of a multivariate experiment. A methodology-based response surface was used to estimate the influence of independent variables such as polymerization time and temperature, as well as the ratio of TEOS and APTES components on the surface charge response function and product yield, and in order to predict the best response values. Analysis of variance showed that when assessing the value of the zeta potential, the polymerization temperature and the ratio of components are statistically significant factors, but on the other hand, when assessing the yield of the finished product, only the ratio of components is significant. The combination of various options for temperature, time and ratio of components allows one to obtain a zeta potential in the range from +61.2 mV to -48.8 mV and a product yield of up to 4.7 g. Evaluation of the data with TGA-DTA, FTIR-ATR, and ELS methods showed an unexpected result, according to which the highest degree of polymerization and the highest surface charge were inherent in an amino-deficient system. Thus, the smaller the amino component in the system (the APTES-TEOS molar ratio is 0.25), the more efficient the polycondensation is over the absorption area of the Si-O-Si band, and the higher the zeta potential.

CO-Preserving Photoinduced Transfer of Cymantrenyl Moiety: a Tandem Experimental and Computational Investigation.

Cyclopentadienyl manganese tricarbonyl (cymantrene) is known to undergo photochemical reactions by releasing one of its CO ligands. Here we present the first example of a photorearrangement of a cymantrenylmethyl fragment, where it retains all its three CO ligands. A tandem experimental and DFT (density functional theory)-based computational investigation allows us to explain this unexpected behavior: the rearrangement, indeed, begins with the release of one CO ligand, but cage effect of the solvent captures this CO molecule, allowing it to rapidly reattach once the rearrangement takes place.

Sample preparation considerations for surface and crystalline properties and ecotoxicity of bare and silica-coated magnetite nanoparticles.

Magnetite (Fe3O4) nanoparticles (NPs) have widely used in various fields, including in medicine, due to their (super)paramagnetic properties. This requires a thorough evaluation of their possible hazardous effects. However, there is no standard procedure for the preparation of oxidation-prone NPs (such as magnetite) before subjecting them to biological assays. In this study we used Fe3O4 NPs (bare and silica-coated) as test samples to compare different preparation methods (ultrasound, centrifugation and filteration of NPs suspensions) based on X-ray and dynamic light scattering analysis and evaluation of microstructure and surface charge. After oxidation and functionalization, all samples retained their superparamagnetic behaviour. The toxicity of NP suspensions obtained by the methods described for Paramecium caudatum ciliates and Sinapis alba plants was evaluated.

Correction: Sample preparation considerations for surface and crystalline properties and ecotoxicity of bare and silica-coated magnetite nanoparticles.

[This corrects the article DOI: 10.1039/D1RA05703K.].

Electrorheological Behavior of Suspensions of Polyimide-Based on the Sodium Salt of 2,5-Diaminobenzenesulfonic Acid.

Electrorheological suspensions (ERS) of polyimide particles with organoelement fragments from the sodium salt of 2,5-diaminobenzene sulfonic acid were obtained for the first time. Their rheological and electrorheological characteristics, their dependence on the parameters of deformation, and the intensity of the external electric field were studied. It was found that the ERS of PI-Na polyimide particles have a significant electrorheological response. Solid-polyimide materials were previously studied using a scanning electron microscope. The effect of the polyimide concentration on the properties of the solution was studied by spectrophotometry. It was shown that polyimide suspension is a result of increasing intensity as the electric field changes the flow type from Newtonian to pseudoplastic due to polarization of the particles and formation of the chain structures along the power lines of the electric field. The influence of temperature on the change of rheological and electrorheological properties of a polyimide ERS in constant electric fields was investigated.