The Doping Effect of Fluorinated Aromatic Solvent on the Rate of Ruthenium Catalysed Olefin Metathesis

A study concerning the effect of using a fluorinated aromatic solvent as the medium for olefin metathesis reactions catalysed by ruthenium complexes bearing N-heterocyclic carbene ligands is presented. The use of fluorinated aromatic hydrocarbons (FAH) as solvents for olefin metathesis reactions catalysed by standard commercially available ruthenium pre-catalysts allows substantially higher yields of the desired products to be obtained,especially in the case of demanding polyfunctional molecules, including natural and biologically active compounds. Interactions between the FAH and the second-generation ruthenium catalysts, which apparently improve the efficiency of the olefin metathesis transformation, have been studied by X-ray structure analysis and computations, as well as by carrying out a number of metathesis experiments. The optimisation of reaction conditions by using an FAH can be regarded as a complementary approach for the design of new improved ruthenium catalysts. Fluorinated aromatic solvents are an attractive alternative medium for promoting challenging olefin metathesis reactions

Protonated nucleobases are not fully ionized and may form stable base pairs in the crystalline state

The following paper presents experimental charge density studies of cytosinium chloride, adeninium chloride hemihydrate, and guanine dichloride crystals based on ultra-high resolution X-ray diffraction data and extensive theoretical calculations. Results confirm that the cohesive energies of the studied systems are dominated by contributions from intermolecular electrostatic interactions, as expected for ionic crystals. Electrostatic interactions energies (Ees) usually constitute 95% of total interaction energies. The Ees energies were several times larger in absolute value when compared, for example, to pairs of neutral nucleobases. However, they were not as big as some of the theoretical calculations predicted. This was because the molecules appeared not to be fully ionized in the studied crystals. Apart from chlorine to protonated nucleobase charge transfer, small but visible, charge redistribution within nucleobase cations was observed. Some pairs of single protonated bases in the studied crystals exhibited attractive interactions (negative values of Ees) or unusually low repulsion despite identical molecular charges. This was because strong hydrogen bonding between bases overcompensated overall cation-cation repulsion, the latter being weakened due to charge transfer and molecular charge density polarization

Consequences of the electronic tuning of latent ruthenium-based olefin metathesis catalysts on their reactivity

Two ruthenium olefin metathesis initiators featuring electronically modified quinoline-based chelating carbene ligands are introduced. Their reactivity in RCM and ROMP reactions was tested and the results were compared to those obtained with the parent unsubstituted compound. The studied complexes are very stable at high temperatures up to 140 °C. The placement of an electron-withdrawing functionality translates into an enhanced activity in RCM. While electronically modified precatalysts, which exist predominantly in the trans-dichloro configuration, gave mostly the RCM and a minor amount of the cycloisomerization product, the unmodified congener, which preferentially exists as its cis-dichloro isomer, shows a switched reactivity. The position of the equilibrium between the cis- and the trans-dichloro species was found to be the crucial factor governing the reactivity of the complexes

Identity in Parents of Children with Autism Spectrum Disorder Based on Interviews with Parents

This thesis is focused on parents of children with autism spectrum disorder, their parental identity and the factors that affect coping with this difficult situation. The thesis is divided into theoretical and practical part. The theoretical part consists of two consecutive sections. The first section describes the main milestones in the history of autism concept, the development of etiology knowledge and the essential characteristics of mentioned diagnosis. This information is contained for the better understanding of what autism means and what are the parents of autistic children going through. The second section is devoted to the healthy children parents identity, its development, but also parental identity of disabled children parents. The focus is on the factors that affect the acceptance of diagnosis and coping with this fact. The empirical part consists of a qualitative study findings. As a method of research was used semi-structured interview, which we realized with the parents of autistic children in three different families. The goal is to describe the factors that impact parental identity of autistic child parents and to compare it with the known theoretical evidences, all based on real parental reports. Keywords: Autism spectrum disorders, diagnostics, development, attitude to child,..

Protonated nucleobases are not fully ionized and may form stable base pairs in the crystalline state

The following paper presents experimental charge density studies of cytosinium chloride, adeninium chloride hemihydrate, and guanine dichloride crystals based on ultra-high resolution X-ray diffraction data and extensive theoretical calculations. Results confirm that the cohesive energies of the studied systems are dominated by contributions from intermolecular electrostatic interactions, as expected for ionic crystals. Electrostatic interactions energies (Ees) usually constitute 95% of total interaction energies. The Ees energies were several times larger in absolute value when compared, for example, to pairs of neutral nucleobases. However, they were not as big as some of the theoretical calculations predicted. This was because the molecules appeared not to be fully ionized in the studied crystals. Apart from chlorine to protonated nucleobase charge transfer, small but visible, charge redistribution within nucleobase cations was observed. Some pairs of single protonated bases in the studied crystals exhibited attractive interactions (negative values of Ees) or unusually low repulsion despite identical molecular charges. This was because strong hydrogen bonding between bases overcompensated overall cation-cation repulsion, the latter being weakened due to charge transfer and molecular charge density polarization