Chitosan-sEPDM and Melatonin-Chitosan-sEPDM Composite Membranes for Melatonin Transport and Release.

Melatonin is the hormone that focuses the attention of the researchers in the medical, pharmaceutical, materials, and membranes fields due to its multiple biomedical implications. The variety of techniques and methods for the controlled release of melatonin is linked to the multitude of applications, among which sports medicine occupies a special place. This paper presents the preparation and characterization of composite membranes based on chitosan (Chi) and sulfonated ethylene-propylene-diene terpolymer (sEPDM). The membranes were obtained by controlled vacuum evaporation from an 8% sEPDM solution in toluene (w/w), in which chitosan was dispersed in an ultrasonic field (sEPDM:Chi = 1:1, w/w). For the comparative evaluation of the membranes' performances, a melatonin-chitosan-sulfonated ethylene-propylene-diene terpolymer (Mel:Chi:sEPDM = 0.5:0.5:1.0, w/w/w) test membrane was made. The prepared membranes were morphologically and structurally characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), energy-dispersive spectroscopy analysis (EDAX), thermal analysis (TG, DSC), thermal analysis coupled with chromatography and infrared analysis, and contact angle measurements, but also from the point of view of performance in the process of transport and release of melatonin in dedicated environments (aqueous solutions with controlled pH and salinity). The prepared membranes can release melatonin in amounts between 0.4 mg/cm2·per day (sEPDM), 1.6 mg/ cm2·per day (Chi/sEPDM), and 1.25 mg/cm2·per day (Mel/Chi/SEPDM).

Hydrogen Sulphide Sequestration with Metallic Ions in Acidic Media Based on Chitosan/sEPDM/Polypropylene Composites Hollow Fiber Membranes System.

This paper presents the preparation and characterization of composite membranes based on chitosan (Chi), sulfonated ethylene-propylene-diene terpolymer (sEPDM), and polypropylene (PPy), and designed to capture hydrogen sulfide. The Chi/sEPDM/PPy composite membranes were prepared through controlled evaporation of a toluene dispersion layer of Chi:sEPDM 1;1, w/w, deposited by immersion and under a slight vacuum (100 mmHg) on a PPy hollow fiber support. The composite membranes were characterized morphologically, structurally, and thermally, but also from the point of view of their performance in the process of hydrogen sulfide sequestration in an acidic media solution with metallic ion content (Cu2+, Cd2+, Pb2+, and/or Zn2+). The operational parameters of the pertraction were the pH, pM, matrix gas flow rate, and composition. The results of pertraction from synthetic gases mixture (nitrogen, methane, carbon dioxide) indicated an efficient removal of hydrogen sulfide through the prepared composite membranes, as well as its immobilization as sulfides. The sequestration and the recuperative separation, as sulfides from an acid medium, of the hydrogen sulfide reached up to 96%, decreasing in the order: CuS > PbS > CdS > ZnS.

pH and pCl Operational Parameters in Some Metallic Ions Separation with Composite Chitosan/Sulfonated Polyether Ether Ketone/Polypropylene Hollow Fibers Membranes.

The development of new composite membranes is required to separate chemical species from aggressive environments without using corrective reagents. One such case is represented by the high hydrochloric acid mixture (very low pH and pCl) that contains mixed metal ions, or that of copper, cadmium, zinc and lead ions in a binary mixture (Cu-Zn and Cd-Pb) or quaternary mixture. This paper presents the obtaining of a composite membrane chitosan (Chi)-sulfonated poly (ether ether ketone) (sPEEK)-polypropylene hollow fiber (Chi/sPEEK/PPHF) and its use in the separation of binary or quaternary mixtures of copper, cadmium, zinc, and lead ions by nanofiltration and pertraction. The obtained membranes were morphologically and structurally characterized using scanning electron microscopy (SEM), high resolution SEM (HR-SEM), energy dispersive spectroscopy analysis (EDAX), Fourier Transform InfraRed (FTIR) spectroscopy, thermogravimetric analysis, and differential scanning calorimetry (TGA-DSC), but also used in preliminary separation tests. Using the ion solutions in hydrochloric acid 3 mol/L, the separation of copper and zinc or cadmium and lead ions from binary mixtures was performed. The pertraction results were superior to those obtained by nanofiltration, both in terms of extraction efficiency and because at pertraction, the separate cation was simultaneously concentrated by an order of magnitude. The mixture of the four cations was separated by nanofiltration (at 5 bars, using a membrane of a 1 m2 active area) by varying two operational parameters: pH and pCl. Cation retention could reach 95% when adequate values of operational parameters were selected. The paper makes some recommendations for the use of composite membranes, chitosan (Chi)-sulfonated poly (ether ether ketone) (sPEEK)-polypropylene hollow fiber (Chi/sPEEK/PPHF), so as to obtain the maximum possible retention of the target cation.

Recuperative Amino Acids Separation through Cellulose Derivative Membranes with Microporous Polypropylene Fiber Matrix.

The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used in the sepa-ration of the amino acids are the most diverse: liquids, ion exchangers, inorganic, polymeric or composites. This paper addresses the recuperative separation of three amino acids (alanine, phe-nylalanine, and methionine) using membranes from cellulosic derivatives in polypropylene ma-trix. The microfiltration membranes (polypropylene hollow fibers) were impregnated with solu-tions of some cellulosic derivatives: cellulose acetate, 2-hydroxyethyl-cellulose, methyl 2-hydroxyethyl-celluloseand sodium carboxymethyl-cellulose. The obtained membranes were characterized in terms of the separation performance of the amino acids considered (retention, flux, and selectivity) and from a morphological and structural point of view: scanning electron microscopy (SEM), high resolution SEM (HR-SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and thermal gravimetric analyzer (TGA). The re-sults obtained show that phenylalanine has the highest fluxes through all four types of mem-branes, followed by methionine and alanine. Of the four kinds of membrane, the most suitable for recuperative separation of the considered amino acids are those based on cellulose acetate and methyl 2-hydroxyethyl-cellulose.

Facile Use of ZnO Nanopowders to Protect Old Manual Paper Documents.

One of the main problems faced by libraries, archives and collectors is the mold degradation of the paper-based documents, books, artworks etc. Microfungi (molds) emerge in regular storage conditions of such items (humidity, usually over 50%, and temperatures under 21 °C). If the removal of the visible mycelium is relatively easy, there is always the problem of the subsequent appearance of mold as the spores remain trapped in the cellulosic, fibrillary texture, which acts as a net. Moreover, due to improper hand hygiene bacteria contamination, old books could represent a source of biohazard, being colonized with human pathogens. An easy and accessible method of decontamination, which could offer long term protection is therefore needed. Here, we present a facile use of the ZnO nanopowders as antimicrobial agents, suitable for cellulose-based products, conferring an extended antibacterial and anti-microfungal effect. The proposed method does not adversely impact on the quality of the cellulose documents and could be efficiently used for biodegradation protection.

Chiral superstructures from homochiral Zn2+ , Co2+ , Fe2+ -2,6-bis (aryl ethylimine)pyridine complexes.

We report the hierarchical supramolecular organization of metallosupramolecular homochiral complexes 1-Λ-(S,S,S,S)-M2+ /1-∆-(R,R,R,R)-M2+ and 2- Λ-(S,S,S,S)-M2+ /2-∆- (R,R,R,R)-M2+ of M2+ = Co2+ , Fe2+ , Zn2+ metal ions with chiral pseudo-terpyridine-type ligands: 1-(S,S) or 1-(R,R) = 2,6-bis (naphthyl ethylimine)pyridine and 2-(S,S) or 2-(R,R) = 2,6-bis (phenyl-ethylimine)pyridine. Circular dichroism measurements in solution were used to confirm the enantiomeric nature of all twelve complexes. For crystal structures of 1- Λ- (S,S,S,S)-M2+ or 1-∆- (R,R,R,R)-M2+ complexes, absolute configurations {∆ (or P), Λ (or M)} were confirmed by refinement of the Flack parameter x: -0.007 ≤ x ≤ 0.11 for the single crystals of 1-Λ-(S,S,S,S)-M2+ /1-∆- (R,R,R,R)-M2+ , 2- Λ- (S,S,S,S)-Fe2+ , and 2-∆- (R,R,R,R)-Co2+ .

Columnar Self-Assemblies of Triarylamines as Scaffolds for Artificial Biomimetic Channels for Ion and for Water Transport.

Triarylamine molecules appended with crown-ethers or carboxylic moieties form self-assembled supramolecular channels within lipid bilayers. Fluorescence assays and voltage clamp studies reveal that the self-assemblies incorporating the crown ethers work as single channels for the selective transport of K+ or Rb+. The X-ray crystallographic structures confirm the mutual columnar self-assembly of triarylamines and crown-ethers. The dimensional fit of K+ cations within the 18-crown-6 leads to a partial dehydration and to the formation of alternating K+ cation-water wires within the channel. This original type of organization may be regarded as a biomimetic alternative of columnar K+-water wires observed for the natural KcsA channel. Supramolecular columnar arrangement was also shown for the triarylamine-carboxylic acid conjugate. In this latter case, stopped-flow light scattering analysis reveals the transport of water across lipid bilayer membranes with a relative water permeability as high as 17 µm s-1.

Orientational disorder in the one-dimensional coordination polymer catena-poly[[bis-(acetyl-acetonato-κ(2) O,O')cobalt(II)]-µ-1,4-di-aza-bicyclo-[2.2.2]octane-κ(2) N (1):N (4)].

The title compound, [Co(C5H7O2)2(C6H12N2)] n , was obtained as a one-dimensional coordination polymer from bis-(acetyl-acetonato)di-aqua-cobalt(II), [Co(acac)2(OH2)2], and 1,4-di-aza-bicyclo-[2.2.2]octane (DABCO), a di-amine with good bridging ability and rod-like spacer function. In the chain complex that extends along the c axis, the Co(II) atom is six-coordinated, the O-donor atoms of the chelating acac ligands occupying the equatorial positions and the bridging DABCO ligands being in trans-axial positions. In the crystal structure, the DABCO ligand is conformationally disordered in a 50:50 manner as a result of its location across a crystallographic mirror plane. The metal-metal distance is very close to that in a related compound exhibiting weak anti-ferromagnetic exchange between the Co(II) ions, and the title compound can thus be useful for obtaining more information about the contribution of different bridges to the magnetic coupling between paramagnetic ions.

Exclusive Hydrophobic Self-Assembly of Adaptive Solid-State Networks of Octasubstituted 9,9'-Spirobifluorenes.

An easy and powerful access to 3,3',6,6'-tetrasubstituted 9,9'-spirobifluorene derivatives with tetrahedral orientation of the peripheral groups (i.e., -I, -CN, -NO2, -CH═O, -COOH, -C≡CH, -4-Py) was developed. The NMR and HRMS results are in agreement with the proposed formula and the solid-state molecular structures obtained by single-crystal X-ray diffraction. They form molecular solids self-assembled via exclusive hydrophobic interactions. Solid-state selection and adaptation can be obtained on the basis of variable compact packing of functional groups present on the 9,9'-spirobifluorene backbone.

New "pyrene box" cages for adaptive guest conformations.

The possibility of controlling the compression extent and the coiling shape of the 1,12-diammoniumdodecane guest is shown by changing the dimensions of the internal space of the host guanidinium 1,3,5,8 pyrene-tetrasulfonate PTS(4-) crystalline capsules by using guanidinium (G(+)), amino-guanidinium (AG(+)), and diaminoguanidinium (A2G(+)) cations.

Crystal structure of tris-(µ-bis-{4-[(pyridin-2-yl-methyl-idene)amino]-phen-yl}methane-κ(4) N,N':N'',N''')dizinc tetra-kis-(tetra-fluorido-borate) aceto-nitrile tris-olvate.

The asymmetric unit of the title compound, [Zn2(C25H20N4)3](BF4)4·3CH3CN, consists of one dinuclear Zn(II) complex cation with a triple-helical [Zn2 L 3](4+) motif (L is bis-{4-[(pyridin-2-yl-methyl-idene)amino]-phen-yl}methane), four BF4 (-) anions and three CH3CN solvent mol-ecules. The Zn⋯Zn separation is 11.3893 (14) Šand the ligands wrap around the two Zn(II) atoms, forming a triple helix as defined by the Zn-N-N-Zn torsion angles of 104.05 (18), 99.06 (19) and 101.40 (19)°. The Zn-N(pyrid-yl) distances in the octahedral ZnN6 coordination sphere are in the range 2.128 (5)-2.190 (5) Šand the Zn-N(imine) distances are in the range 2.157 (5)-2.277 (5) Å.

Weak intermolecular hydrogen and halogen interactions in an isomorphous halogen series of pseudoterpyridine Zn(II) complexes.

The synthesis and characterization of a series of halogen-substituted pseudoterpyridine Zn(II) homoleptic mononuclear complexes, based on ligands L(11)-L(44) [2,6-pyridinedicarboxaldehydebis(p-R-phenylimines), R = F, Cl, Br, I] are reported. Neither of the structures contain relatively strong classical hydrogen bonds (OH···O, NH···O, OH···N, NH···N) and the structure packing is thus determined by a subtle interplay of weaker interactions. Isostructurality of the four halogen analogues is very rare, and in this study -Br, -Cl and -F are found to be isostructural in different degrees, whereas -I is not. Interestingly, although it is closely isostructural to the -Cl and -Br compounds, the F analogue is shown not to form F···O bonds, while the Cl and the Br analogues do form Hal···O bonds. This raises an important question on the role of Hal···O bonds in the structuration of the crystal packing, particularly the stabilization effect. Similarly, while the CH···Hal interaction seems to give one-dimensional cohesion in the -Cl and -Br analogues, this feature is absent in the -F analogue, despite its close isostructurality. CH···O interactions appear to dominate to a first degree the cohesion between the anionic trifluoromethanesulfonate network and the cationic Zn-pyridinedicarboxaldehydebis(p-R-phenylimines) network. The analysis of these interactions is corroborated by reduced density gradient calculations based on promolecular densities.

Self-sorting of metallosupramolecular DCLs via double-level exchange: amplification in solution and solid state modulation.

Interexchanging metallosupramolecular double level imine/ligand Dynamic Constitutional Libraries (DCLs), produce, in solution, the amplification of heteroleptic complexes, which convert into homoleptic complexes via constitutional crystallization.

Triaqua-bis-[4-(meth-oxy-carbon-yl)benzoato-κO]zinc dihydrate.

In the crystal structure of the title complex, [Zn(C(9)H(7)O(4))(2)(H(2)O)(3)]·2H(2)O, the Zn atom and the apical aqua ligand are located on a crystallographic twofold axis, with the Zn(II) ion in a distorted square-pyramidal coordination geometry composed of five O atoms, two from the monodentate methyl-terephthalato group and three from water mol-ecules. The resulting complex and the two hydrate water mol-ecules are inter-connected by O-H⋯O hydrogen bonds.

Pyridine-2,6-dicarboxaldehyde bis[(diphenylmethylidene)hydrazone].

The title compound, C(33)H(25)N(5), belongs to the family of pyridine-2,6-dicarboxaldehyde Schiff bases which possess a terdentate coordinating site (-N=C-C=N-C-C=N-) similar to terpyridine derivatives. The dihedral angles between pairs of terminal rings are 69.67 (9) and 66.23 (9)°. The shortest distance between the centroids of aromatic rings in neighbouring mol-ecules is 3.8080 (14) Å.

Constitutional self-sorting of homochiral supramolecular helical single crystals from achiral components.

Double-helical architectures obtained from achiral ligands and metal ions present supramolecular homochirality in the single -crystal state under constitutional self-sorting.

Self-sorting of equilibrating metallosupramolecular DCLs via constitutional crystallization.

Zn(2+) and Pb(2+) and ligands and self-assemble in solution to generate DCLs of interexchanging metallosupramolecular subcomponents, which convert into robust species of unique stoichiometry via constitutional crystallization.

Tris[4-(2-pyridylmethyl-eneamino)phenol]iron(II) bis-(perchlorate).

In the title compound, [Fe(C(12)H(10)N(2)O)(3)](ClO(4))(2), the metal center is coordinated by six N atoms from the three bidentate chelating ligands in a distorted octa-hedral coordination geometry, with overall formation of the meridional (OC-6-21) isomer. Inter-molecular O-H⋯O hydrogen bonds between the hydroxyl groups of the cation and the counter-anions form an infinite one-dimensional chain in the c-axis direction.