Dynamic Supramolecular Polymers Based on Zinc Bis(diorganophospate)s: Synthesis, Structure and Transformations in Solid State and Solutions.

The synthesis, structure and some properties of coordination polymers composed of linear zinc bis(diorganophospate)s (ZnDOPs) with a general formula of Zn[O2P(OR)2]2 (where R = CH3, C2H5, n-C4H9, or 2-ethylhexyl group) are described. Hybrid (co)polymers obtained by different procedures were characterized by means of powder XRD, DSC, SEM, TGA coupled with mass spectrometry of the evolved gases and rheological measurements, as well as FTIR and NMR techniques. The morphology, thermal transformations and solubility of ZnDOPs strongly depend on the type of organic substituent in the O2P(OR)2 ligands and the thermal history of the sample. Because of this, one can obtain highly crystalline rods, semicrystalline powders, as well as rubbery materials exhibiting a second-order transition below -50 °C. Polymeric chains formed by ZnDOPs undergo a reversible dissociation in polar organic solvents (e.g., methanol, DMSO), which allows for easy modification of their composition and physicochemical properties via a simple exchange of diorganophosphate anions. Some of the ZnDOPs were investigated as the latent curing agents for epoxides. On the basis of rheological and DSC studies, it is evident that ZnDOPs catalyze very effectively the cross-linking process within the 130-160 °C temperature range.

Chemoenzymatic synthesis of enantiomerically enriched diprophylline and xanthinol nicotinate.

A concise chemoenzymatic route toward enantiomerically enriched active pharmaceutical ingredients (API) - diprophylline and xanthinol nicotinate - is reported for the first time. The decisive step is an enantioselective lipase-mediated methanolysis of racemic chlorohydrin-synthon acetate, namely 1-chloro-3-(1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purin-7-yl)propan-2-yl acetate, performed under kinetically-controlled conditions on a preparative 500 mg-scale. The best results in terms of reaction enantioselectivity (E = 14) were obtained for the enantiomers resolution performed with lipase type B from Candida antarctica immobilized on acrylic resin (CAL-B, Novozym 435) suspended in homophasic acetonitrile-methanol mixture. The elaborated biocatalytic system furnished the key chlorohydrin intermediate (in 71% ee and 38% yield), which was then smoothly converted into enantioenriched active agents: (R)-(-)-diprophylline (57% ee) and (S)-(+)-xanthinol nicotinate (65% ee). To support the assignment of absolute configurations of EKR-products as well as to confirm the stereochemical outcome of the remaining reaction steps, docking studies toward the prediction of enantiomers binding selectivity in CAL-B active site as well as the respective chemical correlations with enantiomerically enriched analytical standards obtained from commercially available (R)-(-)-epichlorohydrin, were applied. In addition, single-crystal X-ray diffraction (XRD) analyses were performed for the synthesized optically active APIs furnishing by this manner a first crystal structures of nicotinic acid salt of xanthinol.

A facile lipase-catalyzed KR approach toward enantiomerically enriched homopropargyl alcohols.

Compounds possessing propargylic (prop-2-ynylic) system are very important building blocks for organic chemistry. Among them, preparation of enantiomeric homopropargyl alcohols (but-3-yn-1-ols) constitutes a key-challenge for asymmetric synthesis and thus drawn tremendous attention from the synthetic community in the last few decades. In this work, the catalytic performance of a set of commercial lipases has been investigated for enantioselective transesterification of 1-phenylhomopropargylic alcohols under kinetically-controlled conditions. Lipase from Burckholderia cepacia (BCL) immobilized either on ceramic (Amano PS-C II) or diatomaceous earth (Amano PS-IM) turned out to be the most active and enantioselective enzyme preparations (E ≫ 500) furnishing both resolution products of the racemic 1-phenylbut-3-yn-1-ol in highly enantiomerically enriched form (up > 99% ee). Variable reaction parameters, such as the acyl-group donor reagent as well as solvent, were additionally screened to establish their impact on the stereochemical outcome. For optimal biocatalytic systems established with model substrate, the enzymatic transformations were extended toward preparative-scale KR of 8 other differently para-phenyl-substituted homopropargylic sec-alcohols, which resulted in the synthesis of (S)-alcohols (96-100% ee) and the respective (R)-acetates (92-100% ee) in 19-44% yield, accordingly. Additionally, the crystal structure of (1R)-1-(4-nitrophenyl)but-3-yn-1-yl acetate has been evaluated for the first time and helped to assess stereopreference of the studied BCL.

How and Why Does Helium Permeate Nonporous Arsenolite Under High Pressure?

Investigations into the helium permeation of arsenolite, the cubic, molecular arsenic(III) oxide polymorph As4 O6 , were carried out to understand how and why arsenolite helium clathrate As4 O6 ⋅2 He is formed. High-pressure synchrotron X-ray diffraction experiments on arsenolite single crystals revealed that the permeation of helium into nonporous arsenolite depends on the time for which the crystal is subjected to high pressure and on the crystal history. The single crystal was totally transformed into As4 O6 ⋅2 He within 45 h under 5 GPa. After release of the pressure, arsenolite was recovered and a repeated increase in pressure up to 3 GPa led to practically instant As4 O6 ⋅2 He formation. However, when a pristine arsenolite single crystal was quickly subjected to a pressure of 13 GPa, no helium permeation was observed at all. No neon permeation was observed in analogous experiments. Quantum mechanical computations indicate that there are no specific attractive interactions between He atoms and As4 O6 molecules at the distances observed in the As4 O6 ⋅2 He crystal structure. Detailed analysis of As4 O6 molecular structure changes has shown that the introduction of He into the arsenolite crystal lattice significantly reduces molecular deformations by decreasing the anisotropy of stress exerted on the As4 O6 molecules. This effect and the pΔV term, rather than any specific As⋅⋅⋅He binding, are the driving forces for the formation As4 O6 ⋅2 He.

TFSI and TDI Anions: Probes for Solvate Ionic Liquid and Disproportionation-Based Lithium Battery Electrolytes.

Highly concentrated electrolytes based on Li-salts and chelating solvents, such as glymes, are promising as electrolytes for lithium batteries. This is due to their unique properties, such as higher electrochemical stabilities, compliance with high-voltage electrodes, low volatility and flammability, and inertness toward aluminum current collector corrosion. The nature of these properties originates from the molecular-level structure created in either solvate ionic liquids (SILs) or the less common ionic aggregates by disproportionation reactions. The nature of the anion plays a crucial role, and here, we present a computational study using TFSI and TDI anions as probes, revealing increasing differences upon increased salt concentration. TFSI-based electrolytes preferably form SILs, while TDI-based electrolytes form ionic aggregates. The latter lead to an unexpected creation of "free" cationic species even at (very) high salt concentrations and thus promise of ample lithium ion transport.

Fluorine-free electrolytes for all-solid sodium-ion batteries based on percyano-substituted organic salts.

A new family of fluorine-free solid-polymer electrolytes, for use in sodium-ion battery applications, is presented. Three novel sodium salts withdiffuse negative charges: sodium pentacyanopropenide (NaPCPI), sodium 2,3,4,5-tetracyanopirolate (NaTCP) and sodium 2,4,5-tricyanoimidazolate (NaTIM) were designed andtested in a poly(ethylene oxide) (PEO) matrix as polymer electrolytes for anall-solid sodium-ion battery. Due to unique, non-covalent structural configurations of anions, improved ionic conductivities were observed. As an example, "liquid-like" high conductivities (>1 mS cm-1) were obtained above 70 °C for solid-polymer electrolyte with a PEO to NaTCP molar ratio of 16:1. All presented salts showed high thermal stability and suitable windows of electrochemical stability between 3 and 5 V. These new anions open a new class of compounds with non-covalent structure for electrolytes system applications.

Noncovalent interactions determine the conformation of aurophilic complexes with 2-mercapto-4-methyl-5-thiazoleacetic acid ligands.

We report the synthesis of three gold(i) complexes [Au(H(2)-mmta)(2)]Cl·(3)H(2)O (1), Na(3)[Au(mmta)(2)]·6H(2)O (2) and Na(3)[Au(mmta)(2)]·10.5H(2)O (3) (H(2)-mmta = 2-mercapto-4-methyl-5-thiazoleacetic acid) in which the Au(i) centre is incorporated either in cationic or anionic units of the [Au(SR)(2)](+/-) type depending on the protonation state of the ligand. All structures were characterized by single crystal X-ray analysis and found to exhibit unsupported aurophilic interactions leading to the formation of dimeric [Au(2)(H(2)-mmta)(4)](2+) and [Au(2)(mmta)(4)](6-) species. By applying several ab initio interpretative techniques we examine the character of the intermolecular interactions stabilizing the eclipsed arrangement of the aurophilic dimers formed in 1-3.

Syntheses, crystal structures and antioxidant study of Zn(II) complexes with morin-5'-sulfonic acid (MSA).

The study of modified synthetic procedure of water soluble morin-5'-sulfonic acid sodium salt (NaMSA) involving less aggressive chemicals and carried out at mild conditions was described. The NaMSA salt is a convenient source of anionic morin-5'-sulfonic ligand (MSA) in ion exchange reactions. The coordination ability of MSA ligand towards the zinc cations was investigated in aqueous solution and in solid state. Novel zinc complexes of morin-5'-sulfonate were obtained by a reaction of Zn(NO3)2 with morin-5'-sulfonate in water. Resulting compounds were characterized by single-crystal X-ray diffraction analysis, as well as spectral and thermal methods. The coordination interaction, hydrogen bond and π-π stacking lead to the formation of a 1D chain or 3D coordination polymers. The antioxidant activity of the Zn(II)-MSA complexes was evaluated by means of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging method. In this work, we have shown that the studied compounds are more effective free radical scavengers than the natural flavonoids like plain morin.

Chelating ruthenium phenolate complexes: synthesis, general catalytic activity, and applications in olefin metathesis polymerization.

Cyclic Ru-phenolates were synthesized, and these compounds were used as olefin metathesis catalysts. Investigation of their catalytic activity pointed out that, after activation with chemical agents, these catalysts promote ring-closing metathesis (RCM), enyne and cross-metathesis (CM) reactions, including butenolysis, with good results. Importantly, these latent catalysts are soluble in neat dicyclopentadiene (DCPD) and show good applicability in ring-opening metathesis polymeriyation (ROMP) of this monomer.

Lithium cation conducting TDI anion-based ionic liquids.

In this paper we present the synthesis route and electrochemical properties of new class of ionic liquids (ILs) obtained from lithium derivate TDI (4,5-dicyano-2-(trifluoromethyl)imidazolium) anion. ILs synthesized by us were EMImTDI, PMImTDI and BMImTDI, i.e. TDI anion with 1-alkyl-3-methylimidazolium cations, where alkyl meant ethyl, propyl and butyl groups. TDI anion contains fewer fluorine atoms than LiPF6 and thanks to C-F instead of P-F bond, they are less prone to emit fluorine or hydrogen fluoride due to the rise in temperature. Use of IL results in non-flammability, which is making such electrolyte even safer for both application and environment. The thermal stability of synthesized compounds was tested by DSC and TGA and no signal of decomposition was observed up to 250 °C. The LiTDI salt was added to ILs to form complete electrolytes. The structures of tailored ILs with lithium salt were confirmed by X-ray diffraction patterns. The electrolytes showed excellent properties regarding their ionic conductivity (over 3 mS cm(-1) at room temperature after lithium salt addition), lithium cation transference number (over 0.1), low viscosity and broad electrochemical stability window. The ionic conductivity and viscosity measurements of pure ILs are reported for reference.

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine.

Enantioenriched promethazine and ethopropazine were synthesized through a simple and straightforward four-step chemoenzymatic route. The central chiral building block, 1-(10H-phenothiazin-10-yl)propan-2-ol, was obtained via a lipase-mediated kinetic resolution protocol, which furnished both enantiomeric forms, with superb enantioselectivity (up to E = 844), from the racemate. Novozym 435 and Lipozyme TL IM have been found as ideal biocatalysts for preparation of highly enantioenriched phenothiazolic alcohols (up to >99% ee), which absolute configurations were assigned by Mosher's methodology and unambiguously confirmed by XRD analysis. Thus obtained key-intermediates were further transformed into bromide derivatives by means of PBr3, and subsequently reacted with appropriate amine providing desired pharmacologically valuable (R)- and (S)-stereoisomers of title drugs in an ee range of 84-98%, respectively. The modular amination procedure is based on a solvent-dependent stereodivergent transformation of the bromo derivative, which conducted in toluene gives mainly the product of single inversion, whereas carried out in methanol it provides exclusively the product of net retention. Enantiomeric excess of optically active promethazine and ethopropazine were established by HPLC measurements with chiral columns.

The first facile stereoselectivity switch in the polymerization of rac-lactide--from heteroselective to isoselective dialkylgallium alkoxides with the help of N-heterocyclic carbenes.

The reaction of N-heterocyclic carbene (NHC) with dimeric dialkylgallium alkoxides, acting as nonselective or heteroselective catalysts in the polymerization of rac-LA, leads to highly active and isoselective monomeric Me(2)Ga(NHC)OR catalysts, resulting for the first time in the facile switch of stereoselectivity.

Divergent coordination mode of magnesium and zinc alkyls supported by the bifunctional pyrrolylaldiminato ligand.

The first magnesium and zinc alkyls derived from N-(iso-propyl)-pyrrolylaldimine have been synthesised and structurally characterised: both tBuM(N,N')-type compounds exist as three-coordinate monomers in benzene solution, but in the solid state the magnesium complex is a centrosymmetric dimer with Mg2(mu-N)2 bridges, whereas the zinc complex is a Zn...pi bonded dimer with a pi-coordinated pyrrole unit.

Simple generation of cationic aluminum alkyls and alkoxides based on the pendant arm tridentate schiff base.

The prepared in situ methyl(chloro)aluminum complex (2) from Me2AlCl and the pendant arm tridentate Schiff base (H-SchNMe2) was used to generate the methylaluminum cationic species [(SchNMe2)AlMe]+ in further reaction with 1 equiv of AlCl3 or NaBPh4 as the chloride abstracting reagents. The exposure of the resulting methylaluminum cationic species to an excess of dry dioxygen at 0 degrees C afforded the alkoxyaluminum cationic species, [(SchNMe2)AlOMe]+ or [(SchNMe2)AlOPh]+. The alkoxylaluminum cations proved to be a very efficient catalyst in the polymerization of epsilon-caprolactone.