Maciej Dranka

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.

Controlling the stereoselectivity of rac -LA polymerization by chiral recognition induced the formation of homochiral dimeric metal alkoxides

Using dimeric dialkylgallium and dialkylindium alkoxide catalysts for the polymerization of rac-lactide (rac-LA), we have shown for the first time that the formation of homochiral dimeric species [Me2MOR]2 (M = Ga, In), induced by chiral recognition of monomeric Me2MOR units in the presence of Lewis base, leads to an increase of the heteroselectivity of the ring opening polymerization (ROP) of rac-LA, and therefore provides a new tool for controlling the stereoselectivity of the polymerization of heterocyclic monomers. To explain the origin of the heteroselectivity of the [Me2Ga(μ-OCH(Me)CO2Me)]2/Lewis base system in the ROP of rac-LA, structure of (S,S)-[Me2Ga(μ-OCH(Me)CO2Me)]2 ((S,S)-1) and rac-[Me2Ga(μ-OCH(Me)CO2Me)]2 (1) in the absence and presence of tertiary amines and pyridines was investigated. Studies were further extended by analysis of the structure/activity data for both (S,S)-[Me2In(μ-OCH(Me)CO2Me)]2 ((S,S)-2) and rac-[Me2In(μ-OCH(Me)CO2Me)]2 (2). Contrary to gallium complex 1, which exists in a solution as equimolar mixture of homo- and heterochiral diastereomers, an excess of homochiral (R*,R*)-2 species was observed in the case of 2. For both the Ga and In complexes, the interaction of amines with the metal center increased the tendency for the formation of homochiral species with retention of the dimeric structure in the solution. This tendency was additionally demonstrated by the structure of model dialkylgallium (3) and indium (4) complexes with monoanionic ligands possessing chiral centers in the α-position to the alkoxide oxygen and pyridine functionalities. The polymerization of rac-LA with gallium and indium catalysts (S,S)-1 and (S,S)-2 resulted in the formation of heterotactically enriched polylactide (PLA) (Pr = 0.50–0.85) and (Pr = 0.54–0.72), respectively. The heteroselectivity of the investigated systems was in line with the excess of the homochiral catalytic species. The higher activity of homochiral species activated by amines resulted in a positive non-linear effect between an excess of homochiral (R*,R*)-1 or (R*,R*)-2 catalysts and the heterotacticity of the obtained PLA. The observed dependence of stereoselectivity of rac-LA polymerization on the excess of homochiral species was similar to the asymmetric amplification in enantioselective organic catalysis; however, it is exceptional in polymerization processes.

The self-assembly switching of the group 13 tetrahedral Schiff base complexes by changing the character of coordination centre

The reaction of Et3B with one equivalent of N-substituted salicylideneimine (HsaldR′) yields the monomeric O,N-chelate complexes Et2B(saldR′), where R′ = Me (1) or Ph (2). The crystal structure of the resulting complexes has been determined by X-ray crystallography. The molecular structure of these complexes consists of monomeric four-coordinate chelates and their primary arrangement in the crystal structure is determined by the C–H⋯Oaryloxide hydrogen bonds. An extended crystal structure analysis reveals that the adjacent monomeric moieties of 1 are interconnected by C–Himino⋯O hydrogen bridges resulting in a 1-D motif infinite H-bonded chain, whereas the crystalline complex 2 comprises dimeric molecules linked through a pair of intermolecular C–Harom⋯O interactions. The supramolecular arrangement of both compounds is discussed with relation to the structure of analogous aluminium and gallium complexes, and the role played by the coordination centre on the molecular assembly is analyzed. It is shown that the steric congestion at the hydrogen bond donor and acceptor sites, as a result of changes in the N-alkyl substituents or the coordination centre environment, affect the strength of the intermolecular C–H⋯O hydrogen bonds and may lead to the self-assembly switching of the bidentate Schiff base complexes.

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.

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

Summary 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.

Ternary mixtures of ionic liquids for better salt solubility, conductivity and cation transference number improvement

We hereby present the new class of ionic liquid systems in which lithium salt is introduced into the solution as a lithium cation−glyme solvate. This modification leads to the reorganisation of solution structure, which entails release of free mobile lithium cation solvate and hence leads to the significant enhancement of ionic conductivity and lithium cation transference numbers. This new approach in composing electrolytes also enables even three-fold increase of salt concentration in ionic liquids.

Supramolecular structure of ammonium polyoxoarsenates(III)

Five novel inorganic–organic hybrids have been synthesized and characterised by single-crystal diffraction experiments. The inorganic component comprises polyoxoarsenite chain and the organic one diverse ammonium cations. The crystal structures of ammonium metaoxoarsenate(III) (1), ethylenediammonium metaoxoarsenate(III) (2), benzylammonium metaoxoarsenate(III) (3), methylammonium metaoxoarsenate(III) (4) and ethanolammonium metaoxoarsenate(III) (5) are reported and their supramolecular organisation uncovered. 1D hydrogen bonded cation–anion structural units are formed in all five compounds and it is shown that (AsO−2)n chains act as structure-directing motifs. The polyoxoarsenite chains are spanned by a series of O⋯H–N–H⋯O hydrogen bridges via ammonium cations and stiffened by secondary As⋯O interactions, comprising the primary structure. The electroneutral chains are connected by N–H⋯O hydrogen bonds into layers of secondary structure. These layers are joined to form a 3D tertiary structure by a variety of linkers ranging from hydrogen bonds, van der Waals and C–H⋯π interactions to covalent bridges.

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.

Dialkylgallium alkoxides – a tool for facile and stereoselective synthesis of PLA–drug conjugates

Herein, a method for the synthesis of PLA-(β-blocker) conjugates with a tunable stereostructure of the PLA fragment is demonstrated using stereoselective [R2Ga(μ-β-blocker)]2 catalysts and [R2Ga(μ-OR)]2/H-(β-blocker) catalytic systems for the ring-opening polymerisation (ROP) and immortal ring-opening polymerisation (iROP) of racemic lactide (rac-LA), respectively.