Ionic liquids as silica deactivating agents in gas chromatography for direct analysis of primary amines in water

Analysis of primary amines in aqueous samples remains a challenging analytical issue. The preferred approach by gas chromatography is hampered by interactions of free silanol groups with the highly reactive amine groups, resulting in inconsistent measurements. Here, we report a method for direct analysis of aliphatic amines and diamines in aqueous samples by gas chromatography (GC) with silanol deactivation using ionic liquids (ILs). ILs including trihexyl(tetradecyl)phosphonium bis 2,4,4-(trimethylpentyl)phosphinate (Cyphos IL-104), 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide [pmim][Tf(2)N] and N″-ethyl-N,N,N',N'-tetramethylguanidinium tris(pentafluoroethyl)trifluorophosphate [etmg][FAP] were tested as deactivating media for the GC liner. Solutions of these ILs in methanol were injected in the system prior to the analysis of primary amines. Butane-1,4-diamine (putrescine, BDA) was used as a reference amine. The best results were obtained using the imidazolium IL [pmim][Tf(2)N]. With this deactivator, excellent reproducibility of the analysis was achieved, and the detection limit of BDA was as low as 1mM. The applicability of the method was proven for the analysis of two different primary amines (C4-C5) and pentane-1,5-diamine.     

Interaction of Liposomal Formulations of Meta-tetra(hydroxyphenyl)chlorin (Temoporfin) with Serum Proteins: Protein Binding and Liposome Destruction

mTHPC is a non polar photosensitizer used in photodynamic therapy. To improve its solubility and pharmacokinetic properties, liposomes were proposed as drug carriers. Binding of liposomal mTHPC to serum proteins and stability of drug carriers in serum are of major importance for PDT efficacy; however, neither was reported before. We studied drug binding to human serum proteins using size‐exclusion chromatography. Liposomes destruction in human serum was measured by nanoparticle tracking analysis (NTA). Inclusion of mTHPC into conventional (Foslip^®) and PEGylated (Fospeg^®) liposomes does not affect equilibrium serum protein binding compared with solvent‐based mTHPC. At short incubation times the redistribution of mTHPC from Foslip^® and Fospeg^® proceeds by both drug release and liposomes destruction. At longer incubation times, the drug redistributes only by release. The release of mTHPC from PEGylated vesicles is delayed compared with conventional liposomes, alongside with greatly decreased liposomes destruction. Thus, for long‐circulation times the pharmacokinetic behavior of Fospeg^® could be influenced by a combination of protein‐ and liposome‐bound drug. The study highlights the modes of interaction of photosensitizer‐loaded nanovesicles in serum to predict optimal drug delivery and behavior in vivo in preclinical models, as well as the novel application of NTA to assess the destruction of liposomes.     

α-Amidoalkylating agents from N-acyl-α-amino acids: 1-(N-acylamino)alkyltriphenylphosphonium salts

N-Acyl-α-amino acids were efficiently transformed in a two-step procedure into 1-N-(acylamino)alkyltriphenylphosphonium salts, new powerful α-amidoalkylating agents. The effect of the α-amino acid structure, the base used [MeONa or a silica gel-supported piperidine (SiO(2)-Pip)], and the main electrolysis parameters (current density, charge consumption) on the yield and selectivity of the electrochemical decarboxylative α-methoxylation of N-acyl-α-amino acids (Hofer-Moest reaction) was investigated. For most proteinogenic and all studied unproteinogenic α-amino acids, very good results were obtained using a substoichiometric amount of SiO(2)-Pip as the base. Only in the cases of N-acylated cysteine, methionine, and tryptophan, attempts to carry out the Hofer-Moest reaction in the applied conditions failed, probably because of the susceptibility of these α-amino acids to an electrochemical oxidation on the side chain. The methoxy group of N-(1-methoxyalkyl)amides was effectively displaced with the triphenylphosphonium group by dissolving an equimolar amount of N-(1-methoxyalkyl)amide and triphenylphosphonium tetrafluoroborate in CH(2)Cl(2) at room temperature for 30 min, followed by the precipitation of 1-N-(acylamino)alkyltriphenylphosphonium salt with Et(2)O.     

Amphiphilic meso(sulfonate ester fluoroaryl)porphyrins: refining the substituents of porphyrin derivatives for phototherapy and diagnostics

A set of amphiphilic fluorinated porphyrins appended with sulfonate ester groups were synthesized and fully characterized. The reaction proceeds efficiently, with high yields, with an improved methodology. Their potential use as imaging and phototherapeutic agents was assessed measuring relevant photophysical properties. It is shown that these porphyrins have good photostability, long triplet lifetimes (between 47 μs and 102 μs), high singlet oxygen quantum yields (0.74≤FD≤1.00), low fluorescence quantum yields (<0.04) and sharp 19F NMR peaks. The data on the new meso(sulfonate ester fluoroaryl)porphyrins illustrate the potential of perfluorinated sulfonate esters to improve physical properties relevant for cancer imaging and photodynamic therapy.     

Solid electrolyte interphase formation on metallic lithium

Solutions of three salts (LiBF₄, LiNTf₂, LiPF₆) in N-methyl-2-pyrrolidone (NMP), selected arbitrarily as a reference solvent, were investigated by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy techniques. The lithium surface in contact with LiPF₆ in NMP electrolyte was covered with a protective layer (SEI) which morphology comprise small particles (of ca. 0.2 μm in radius). This salt was selected for further studies. The impedance of the Li|(LiPF₆ in NMP?+?additive)|Li system was measured immediately after cell assembly and after galvanostatic charging/discharging. Fifteen different additives (10 wt.%) were used. The efficiency of individual additives was evaluated in terms of the Li|electrolyte system resistance (ΔR) or total cell impedance reduction, both deduced from EIS. Some of the additives were able to form the SEI layer and to reduce resistance/impedance of the Li|electrolyte interphase. In such cases, the lithium surface was covered with relatively uniform conglomerates, or regions separated by cracks, of ca. 1–2 μm in dimension.     

Hydrogenolysis goes bio: from carbohydrates and sugar alcohols to platform chemicals

In view of the diminishing oil resources and the ongoing climate change, the use of efficient and environmentally benign technologies for the utilization of renewable resources has become indispensible. Therein, hydrogenolysis reactions offer a promising possibility for future biorefinery concepts. These reactions result in the cleavage of C-C and C-O bonds by hydrogen and allow direct access to valuable platform chemicals already integrated in today's value chains. Thus, hydrogenolysis bears the potential to bridge currently available technologies and future biomass-based refinery concepts. This Review highlights past and present developments in this field, with special emphasis on the direct utilization of cellulosic feedstocks.     

Synthesis and optoelectronic properties of hexahydroxylated 10-O-R-substituted anthracenes via a new modification of the Friedel-Crafts reaction using O-protected ortho-acetal diarylmethanols

A new modification of the Friedel-Crafts type intramolecular cyclization involving O-protected ortho-acetal diarylmethanols as a new type of reactant, was carried out for the first time in a medium containing a large amount of water at room temperature and enabled synthesis of a series of electron-rich, hexahydroxylated 10-O-R-substituted anthracenes, where R is an alkyl (Me, nBu, n-C(16)H(33)) or arylalkyl group (CH(2)Ph, CH(2)-2-Napht, CH(2)C(6)H(4)CH(2)OAr) and also evaluation of their electronic and optoelectronic properties in solution, crystal, and solid thin film. In this transformation, a central 10-O-R-substituted benzene ring was formed, fused to rings originating from two independent aromatic aldehydes. The reaction proceeded via two identified mechanisms involving acetal and/or free aldehyde groups. The acid sensitive acetal and dibenzyl alkoxy functions have never been used together in the intramolecular Friedel-Crafts type cyclization. The new compounds revealed deep blue fluorescence and quantum yields in solution around 0.3. The electrical properties investigated for thin films obtained by vacuum deposition on glass were 10-O-R-substituent dependent and showed much faster transient current decay in the case of the 10-O-CH(2)Ph derivative than for the material with a 10-O-Me substituent (the lifetime of charge carriers was 25 times shorter in this case). The AFM images of thin films, Stokes shifts, and X-ray analysis of π-stacking interactions in crystals of the new materials have been also obtained.     

Crystal structure, electronic properties and cytotoxic activity of palladium chloride complexes with monosubstituted pyridines

Palladium(II) complexes attract great attention due to their remarkable catalytic and biological activity. In the present study X-ray characterization, UV-Vis and Time-Dependent Density Functional Theory (TD-DFT) calculations for six PdCl(2)(XPy)(2) complexes (where: Py = pyridine; X = H, CH(3) or Cl) were applied in order to investigate substituent effects on their crystal structures and electronic properties and to combine the results with their catalytic and cytotoxic activity. The structures of complexes PdCl(2)(3-MePy)(2), PdCl(2)(4-MePy)(2) and PdCl(2)(2-ClPy)(2), have been described for the first time and we compared our results with available data for the whole series of six complexes. All compounds exhibit a square planar coordination geometry in which the palladium ion coordinates two nitrogen atoms of pyridine ligands and two chlorine atoms in trans positions. For complexes with ortho substituted XPy ligands a cis disposition of substituents takes place, whereas for other ligands: 3-MePy and 3-ClPy--the substituents are in trans positions. For XPy the energies of π-π* and n-π* transitions depend on the position and nature of the X substituent in the XPy ring. After complex formation a hipsochromic shift (24-34 nm) of π-π* and a bathochromic shift of n-π* bands are observed. The UV-Vis spectra of PdCl(2)(XPy)(2) confirm that square planar coordination geometry of complexes I-VI and two dπ-π* transitions are expected. With the help of the TD-DFT calculations we proved that dπ-π* transitions in solutions of PdCl(2)(XPy)(2) complexes result from MLCT (metal-to-ligand charge transfer) with contribution from chlorine atoms to palladium. We also studied substituent effects on cytotoxic properties of Pd(II) complexes against the human breast cancer cell line MCF7, the human prostate cancer cell line PC3, and the human T-cell lymphoblast-like cell line CCRF. The studied complexes were the most active against the CCRF cell line and less or even no cytotoxic effect was observed for PC3 cells. Complexes with MePy ligands showed increased cytotoxic activity compared to unsubstituted pyridine ligands.     

XAFS investigations of nitrided NbN–SiO2 sol–gel derived films

This work presents the results of the structural analysis of xNbN–(100-x)SiO₂ (x = 100, 80, 60 mol%) thin films by X-ray absorption spectroscopy (XAS). To prepare the films, thermal nitridation of sol–gel derived coatings have been performed. The resulting films have a granular structure with NbN grains distributed in the SiO₂ matrix. The size of the grains depends on the NbN/SiO₂ molar ratio. A detailed X-ray absorption fine structure (XAFS) data analysis shows that in all the samples both nitrogen and oxygen atoms are present as nearest neighbours of Nb. The intra-granular phase is an ordered NbN phase, whereas the shells around the grains are formed mainly by an oxide phase and, possibly, by other niobium nitride phases (probably with low nitrogen content). Two possible origins of the inter-granular oxide phase were considered: incomplete nitridation of Nb₂O₅ and addition of SiO₂. Both of them are connected with the sample preparation method. The obtained XAS results allowed us to correlate the thickness and stoichiometry of the films under study with the electronic structure of the Nb ions and with the local geometric structure in their environment.     

Morphology of struvite crystals as an evidence of bacteria mediated growth

Influence of Proteus mirabilis on the growth, morphology and size of struvite crystals in artificial urine has been studied. The growth in the presence of Proteus mirabilis shows formation of struvite crystals of more regular habits compared with that in the absence of bacteria. This implies that in the presence of Proteus mirabilis, struvite crystals grow with relative growth rates within smaller range of variability compared to the absence of bacteria. The results show that bacteria affect size and struvite morphology while the habit remains almost unchanged. It is suggested that the changes in struvite crystal morphology are induced by the presence of Proteus mirabilis. Microorganism's negatively charged residues interact electrostatically with positive ions which outcrop given surfaces and lead to an enhanced expression of these surfaces. This means that microorganisms actively mediate in growth processes. Therefore, the investigations provide evidence for the importance of biological regulation in crystallization process.