Search results for "Intermolecular"

Studies of intermolecular heterogeneity distribution in ethylene/1-hexene copolymers using DSC method

2002

The investigation of the intermolecular composition distribution of an ethylene/1-hexene copolymers using DSC method has been carried out. The known methods: step crystallization (SC) and successive self-nucleation/annealing (SSA) have been adapted for this purpose, and particularly, the optimal condition of the process have been chosen to enable the best fractional crystallization of the copolymer. The method has been applied for fractionation of two ethylene/1-hexenecopolymers synthesized with supported vanadium and zirconocene catalysts and having similar concentrations of 1-hexene. Although metallocene catalysts are known from their more homogeneous structure of active sites in comparis…

Orientation and molecular contacts of melatonin confined into AOT and lecithin reversed micellar systems

2008

Abstract The state of increasing amounts of melatonin (MLT) confined in dry AOT or lecithin reversed micelles dispersed in CCl 4 has been investigated by UV–vis and 1 H NMR spectroscopies. The experimental results are consistent with MLT totally entrapped in reversed micelles, as a consequence of specific melatonin/surfactant interaction; the main driving force of the MLT solubilization in the core of reversed micelles is the establishment of H-bonding between the MLT NH groups (both indolic and amidic) and the head group of surfactants. The short contacts deduced from intermolecular NOEs are accounted for by favourable interactions between the surfactant's polar head and the H7–NH–H2 fragm…

The Effect of the Side Chain on Gelation Properties of Bile Acid Alkyl Amides

2021

Abstract Six bile acid alkyl amide derivatives were studied with respect to their gelation properties. The derivatives were composed of three different bile acids with hexyl or cyclohexyl side chains. The gelation behaviour of all six compounds were studied for 36 solvents with varying polarities. Gelation was observed mainly in aromatic solvents, which is characteristic for bile‐acid‐based low molecular weight gelators. Out of 108 bile acid‐solvent combinations, a total of 44 gel systems were formed, 28 of which from lithocholic acid derivatives, only two from deoxycholic acid derivatives, and 14 from cholic acid derivatives. The majority of the gel systems were formed from bile acids with…

Communication between iron(II) building blocks in cooperative spin transition phenomena

2003

[EN] In the present article we discuss the cooperative nature of the spin crossover phenomenon in iron(II) complexes, providing a perspective of the state of the art in this area. The first aspect we discuss is the role of the intermolecular interactions, more precisely the ¿-interactions, in mononuclear complexes. We show that by playing with the nature of the ligands, aliphatic, aromatic, or extended aromatic, it is possible to create stronger cohesive forces and receive a more cooperative response from the compound. In the next step the singular family of bipyrimidine-bridged iron(II) dinuclear compounds is presented as the simplest example of polynuclear spin crossover complexes exhibit…

Persistence of oxidation state III of gold in thione coordination

2017

Ligands N,N'-tetramethylthiourea and 2-mercapto-1-methyl-imidazole form stable Au(III) complexes [AuCl3(N,N'-tetramethylthiourea)] (1) and [AuCl3(2-mercapto-1-methyl-imidazole)] (2) instead of reducing the Au(III) metal center into Au(I), which would be typical for the attachment of sulfur donors. Compounds 1 and 2 were characterized by spectroscopic methods and by X-ray crystallography. The spectroscopic details were explained by simulation of the UV-Vis spectra via the TD-DFT method. Additionally, computational DFT studies were performed in order to find the reason for the unusual oxidation state in the crystalline materials. The preference for Au(III) can be explained via various weak in…

Halogen Bonds in Square Planar 2,5-Dihalopyridine-Copper(II) Bromide Complexes

2018

Experimental FTIR-MI and Theoretical Studies of Isocyanic Acid Aggregates

2023

Homoaggregates of isocyanic acid (HNCO) were studied using FTIR spectroscopy combined with a low-temperature matrix isolation technique and quantum chemical calculations. Computationally, the structures of the HNCO dimers and trimers were optimized at the MP2, B3LYPD3 and B2PLYPD3 levels of theory employing the 6-311++G(3df,3pd) basis set. Topological analysis of the electron density (AIM) was used to identify the type of non-covalent interactions in the studied aggregates. Five stable minima were located on the potential energy surface for (HNCO)2, and nine were located on the potential energy surface for (HNCO)3. The most stable dimer (D1) involves a weak, almost linear N-H⋯N hydrog…

Light-induced, site-selective isomerization of glyoxylic acid in solid xenon

2014

Abstract The isomerization of glyoxylic acid (GA) and its water complex was studied in a low temperature xenon matrix. The aim of these studies was to understand how xenon environment affects the cis-trans GA interconversion upon near infrared irradiation. In solid xenon, the GA conformers are embedded in two different matrix sites. These show up as different vibrational bands of GA that exhibit different kinetic rates of isomerization. Upon complexation with water, the isomerization process slows down. Xenon matrix appears not to affect energy relaxation process via intramolecular or intermolecular hydrogen bond as compared with previous experiments in an argon.

Gold(I)-catalyzed intermolecular oxyarylation of alkynes: unexpected regiochemistry in the alkylation of arenes.

2009

The reaction between acetylenes and sulfoxides, studied as a test case for gold-catalyzed intermolecular addition, provides the oxyarylation compounds 3 in good yields. Unpredictably, in all cases a single regioisomer arising from the electrophilic aromatic alkylation at the position adjacent to the sulfur atom is obtained instead of the expected Friedel−Crafts regioisomer. A new concerted mechanism based on DFT calculations is proposed to account for the products in this intermolecular gold(I)-catalyzed reaction.

The enrichment ratio of atomic contacts in crystals, an indicator derived from the Hirshfeld surface analysis

2014

An enrichment ratio is derived from the decomposition of the crystal contact surface between pairs of interacting chemical species. The propensity of different contact types to form is investigated.