Copolymers based on butyl methacrylate and β-Cyclodextrin: Synthesis and structure

Copolymers based on butyl methacrylate and urethane methacrylate containing side cyclodextrin fragments are prepared. With the use of IR spectroscopy, SAXS, WAXS, and DSC, it has been shown that microphase separation in the said copolymers is hampered by cyclodextrin moieties and that the chemical nature and structure of blocks occurring in side chains play the key role in the formation of micro-and macro-phase structures in the polymer systems under consideration.     

Electrodeposition of Co–W coatings from boron gluconate electrolyte with a soluble tungsten anode

Conditions were determined in which an active anodic dissolution of tungsten is observed in a borongluconate electrolyte used to obtain Co–W coatings (pH ~6.5) and the nature of critical currents of transition to the passivation was found, which makes it possible to use the tungsten anode as a soluble electrode. The anodic dissolution of tungsten occurs under these conditions with a current efficiency of 90–100%, which, in contrast to the case of a graphite anode, does not lead to an additional oxidation of the electrolyte components and polymerization in solution; in combination with the decrease in the concentration of tungstate ions, this reduces the electrolyte performance. It was shown that the use of a soluble tungsten anode in obtaining nanocrystalline cobalt–tungsten coating can improve the electrolyte performance due to the rise in the current efficiency of electrodeposition and to the increase in the microhardness of the coatings in comparison with the case of an insoluble graphite anode.     

Synthesis and Chemical Reactivity of a 6‐Me‐3,2‐Hydroxypyridinone Dithiazolide with Primary Amines: A route to New Hexadentate Chelators for Hard Metal(III) Ions

A hydroxypyridinone building block, bifunctionalized with thiazoline, has been prepared from orthogonally protected 2‐(3‐(benzyloxy)‐4‐(ethoxycarbonyl)‐6‐methyl‐2‐oxopyridin‐1(2H)‐yl) acetic acid. The reactivity of the dithiazolide has been explored with two primary amines, leading to the synthesis and characterization of four new hexadentate ligands. Their complexes with selected hard trivalent ions pertinent to potential molecular imaging applications have been surveyed.     

Combined crystallographic and solution molecular dynamics study of allosteric effects in ester and ketone p-tert-butylcalix[4]arene derivatives and their complexes with acetonitrile, Cd(II), and Pb(II)

We describe here a procedure to bridge the gap in the field of calixarene physicochemistry between solid-state atomic-resolution structural information and the liquid-state low-resolution thermodynamics and spectroscopic data. We use MD simulations to study the kinetics and energetics involved in the complexation of lower rim calix[4]arene derivatives (L), containing bidentate ester (1) and ketone (2) pendant groups, with acetonitrile molecule (MeCN) and Cd(2+) and Pb(2+) ions (M(2+)) in acetonitrile solution. On one hand, we found that the prior inclusion of MeCN into the calix to form a L(MeCN) adduct has only a weak effect in preorganizing the hydrophilic cavity toward metal ion binding. On the other hand, the strong ion-hydrophilic cavity interaction produces a wide open calix which enhances the binding of one MeCN molecule (allosteric effect) to stabilize the whole (M(2+)) L(MeCN) bifunctional complex. We reach two major conclusions: (i) the MD results for the (M(2+)) 1(MeCN) binding are in close agreement with the "endo", fully encapsulated, metal complex found by X-ray diffraction and in vacuo MD calculations, and (ii) the MD structure for the more flexible 2 ligand, however, differs from the also endo solid-state molecule. In fact, it shows strong solvation effects at the calixarene lower bore by competing MeCN molecules that share the metal coordination sphere with the four CO oxygens of an "exo" (M(2+)) 2(MeCN) complex.     

Heat exchange at agitation in apparatus with upright heat-exchange devices

The heat exchange is examined in apparatus with agitation devices and installed heat exchange elements using semi-empirical theory of a turbulent transfer. We determined hydrodynamical parameters near a heat transfer surface.     

Enantioselective sorption of alcohols in a homochiral metal-organic framework

Single-crystal X-ray diffraction study reveals the host-guest interactions between a homochiral metal-organic framework and two enantiomers of a chiral alcohol providing the key driving force for the enantioselective sorption of alcohols in the framework.     

Covalent Functionalization of Strained Graphene

An enhancement of the chemical activity of graphene is evidenced by first‐principles modelling of the chemisorption of hydrogen, fluorine, oxygen and hydroxyl groups on strained graphene. For the case of negative strain or compression, chemisorption of the single hydrogen, fluorine or hydroxyl group is energetically more favourable than those of their pairs on different sublattices. This behaviour stabilizes the magnetism caused by the chemisorption being against its destruction by the pair formations. Initially flat, compressed graphene is shown to buckle spontaneously right after chemisorption of single adatoms. Unlike hydrogenation or fluorination, the oxidation process turns from the endothermic to exothermic for all types of the strain and depends on the direction of applied strains. Such properties will be useful in designing graphene devices utilizing functionalization as well as mechanical strains.     

Cation/anion recognition by a partially substituted lower rim calix[4]arene hydroxyamide, a ditopic receptor

The complexation ability of a partially substituted lower rim calix[4]arene hydroxyamide derivative, 25,27-bis[N-(2-hydroxy-1,1-bishydroxymethylethyl)amino- carbonylmethoxy]calix[4]arene-26,28-diol, 1, for cations and anions was investigated through (1)H NMR, conductometry, spectrophotometry, and calorimetry in dipolar aprotic media. (1)H NMR studies of 1 in the deuterated solvents (acetonitrile, methanol, and dimethylsulfoxide) reflect ligand-solvent interactions in methanol and dimethylsulfoxide. As far as the cations are concerned, a selectivity peak is found when standard Gibbs energies of complexation of 1 with cations (alkaline-earth, zinc, and lead) are plotted against corresponding data for cation hydration. This finding reflects the key role played by the desolvation and binding processes in the overall complexation of this receptor and these cations in acetonitrile. This is also interpreted in terms of enthalpy and entropy data. Factors such as, the nature and the arrangement of donor atoms in the hydrophilic cavity of the ligand on cation complexation process, are discussed. This paper also addresses anion complexation processes. It is found that 1 interacts through hydrogen bond formation with fluoride, dihydrogen phosphate, and pyrophosphate in acetonitrile and N,N-dimethylformamide. The thermodynamics associated with these processes is fully discussed taking into account literature data involving calix[4]pyrroles and these anions in these solvents. Previous work regarding the water solubility of these ligands is discussed. It is concluded that 1 behaves as a ditopic ligand in dipolar aprotic media.     

Thermodynamic and electrochemical aspects ofp-tert-butylcalix[n]arenes (n=4, 6, 8) and their interactions with amines

Attention is drawn to the need of detailed thermodynamics in calixarene chemistry. The reasons for increasing efforts in this area are underlined and suggestions for new issues to be addressed are given. The solution thermodynamics ofp-tert-butylcalix[n]arenes (n=4, 6, 8) is discussed with particular reference to transfer Gibbs energies which reflect the selective solvation that the tetramer and the octamer undergo in the various solvents. This is followed by recent solution studies on amine-p-tert-butylcalix[n]arene (n=4, 6, 8) in nitrobenzene and in benzonitrile at 298.15 K which indicate the lower acidic character of the tetramer relative to the hexamer and the octamer in these solvents. As an implication of these results, very low conductivities are observed in studies involving the interaction of the former with amines. Thus, thermodynamic studies suggest thatp-tert-butylcalix[4]arene interacts with triethylamine in benzonitrile and in nitrobenzene through hydrogen bonding or ion-pair formation. A thermodynamic cycle is used to investigate the effect associated with the interaction of the amine with the tetramer in these solvents.This paper is dedicated to the commemorative issue on the 50th anniversary of calixarenes.     

Double-cavity calix[4]pyrrole derivative with enhanced capacity for the fluoride anion

A double-cavity calix[4]pyrrole derivative, meso-tetramethyl-tetra[N-(2-phenoxyethyl)-N'-phenylurea]calix[4]pyrrole, 1, with enhanced hosting ability for the fluoride anion has been designed and characterized. Its interaction with anions (fluoride, chloride, bromide, iodide, dihydrogen phosphate, hydrogen sulfate, perchlorate, nitrate, and trifluoromethane sulfonate) was qualitatively and quantitatively assessed through 1H NMR, conductance, and calorimetric studies. The outcome of these investigations demonstrates that 1 interacts only with fluoride and dihydrogen phosphate anions in dipolar aprotic media. However, the composition of these complexes differs in that two units of fluoride are taken per unit of 1, while a 1:1 anion/ligand complex is formed with the dihydrogen phosphate anion. Results from the 1H NMR studies are striking in that these not only provide information about the active sites of the ligand-anion interaction but also allow the establishment of the sequence of events taking place during fluoride complexation. Thus, hydrogen-bond formation between the pyrrolic hydrogen and the fluoride anion is followed by the uptake of a second anion through the same type of interaction, but with the phenyl urea. It is also the latter group that is responsible for the interaction of 1 with the dihydrogen phosphate anion. Finally, this paper illustrates the importance of structural information for the interpretation of the thermodynamics associated with these systems.