Dielectric and Structural Properties of the Hybrid Material Polyvinylidene Fluoride-Bacterial Nanocellulose-Based Composite.

In the search for environmentally friendly materials with a wide range of properties, polymer composites have emerged as a promising alternative due to their multifunctional properties. This study focuses on the synthesis of composite materials consisting of four components: bacterial nanocellulose (BNC) modified with magnetic Fe3O4, and a mixture of BaTiO3 (BT) and polyvinylidene fluoride (PVDF). The BT powder was mechanically activated prior to mixing with PVDF. The influence of BT mechanical activation and BNC with magnetic particles on the PVDF matrix was investigated. The obtained composite films' structural characteristics, morphology, and dielectric properties are presented. This research provides insights into the relationship between mechanical activation of the filler and structural and dielectric properties in the PVDF/BT/BNC/Fe3O4 system, creating the way for the development of materials with a wide range of diverse properties that support the concept of green technologies.

Self-Assembly and Biorecognition of a Spirohydantoin Derived from α-Tetralone: Interplay between Chirality and Intermolecular Interactions.

A racemic spirohydantoin derivative with two aromatic substituents, a tetralin and a 4-methoxybenzyl unit, was synthesized and its crystal structure was determined. To define the relationship between molecular stereochemistry and spatial association modes, development of the crystal packing was analyzed through cooperativity of intermolecular interactions. Homo and heterochiral dimeric motifs were stabilized by intermolecular N-H⋅⋅⋅O, C-H⋅⋅⋅O, C-H⋅⋅⋅π interactions and parallel interactions at large offsets (PILO), thus forming alternating double layers. The greatest contribution to the total stabilization came from a motif of opposite enantiomers linked by N-H⋅⋅⋅O bonds (interaction energy=-13.72 kcal/mol), followed by a homochiral motif where the 4-methoxybenzyl units allowed C-H⋅⋅⋅π, C-H⋅⋅⋅O interactions and PILO (interaction energy=-11.56 kcal/mol). The number of the contact fragments in the environment of the tetralin unit was larger, but the 4-methoxybenzyl unit had greater contribution to the total stabilization. The statistical analysis of the data from the Cambridge Structural Database (CSD) showed that this is a general trend. The compound is a potential inhibitor of kinase enzymes and antigen protein-coupled receptors. A correlation between the docking study and the results of the CSD analysis can be drawn. Due to a greater flexibility, the 4-methoxybenzyl unit is more adaptable for interactions with the biological targets than the tetralin unit.

Diaquabis(2,2'-dipyridylamine)M(II) Terephthalate Dihydrates, M(II) = Ni, Co: Synthesis, Crystal Structures, Thermal and Magnetic Properties.

Two new isostructural M(II) (M = Ni, Co) complexes with 2,2'-dipyridylamine (dipya) and dianion of terephthalic acid (H2tpht), [M(dipya)2(H2O)2](tpht) ∙ 2H2O, have been synthesized by ligand exchange reaction and characterized by single-crystal X-ray diffraction, FTIR spectroscopy, TG/DSC analysis and magnetic measurements. The crystal structures of [M(dipya)2(H2O)2](tpht) ∙ 2H2O consist of discrete complex units in which M(II) adopts deformed octahedral geometries. Two dipya ligands and two water molecules are coordinated to M(II) atom, tpht acts as a counter ion, while additional two water molecules remained uncoordinated. By numerous hydrogen bonds, all structural fragments are connected in three different chains which extend along [100], [010] and [001] directions, giving as a result a complex 3D network. The stabilization of 3D structure is accomplished by non-covalent face to face π-π interactions among pyridyl ring of dipya and benzene ring of tpht from adjacent chains. Towards the applied magnetic field, the both complexes exhibited almost perfect paramagnetic behavior.

Nanoscale zerovalent iron (nZVI) supported by natural and acid-activated sepiolites: the effect of the nZVI/support ratio on the composite properties and Cd2+ adsorption.

Natural (SEP) and partially acid-activated (AAS) sepiolites were used to prepare composites with nanoscale zerovalent iron (nZVI) at different (SEP or AAS)/nZVI ratios in order to achieve the best nZVI dispersibility and the highest adsorption capacity for Cd2+. Despite the higher surface area and pore volume of AAS, better nZVI dispersibility was achieved by using SEP as the support. On the other hand, a lower oxidation degree was achieved during the synthesis using AAS. X-ray photoelectron spectroscopy (XPS) analysis of the composite with the best nZVI dispersibility, before and after Cd2+ adsorption, confirmed that the surface of the nZVI was composed of oxidized iron species. Metallic iron was not present on the surface, but it was detected in the subsurface region after sputtering. The content of zerovalent iron decreased after Cd2+ adsorption as a result of iron oxidation during Cd2+ adsorption. The XPS depth profile showed that cadmium was present not only at the surface of the composite but also in the subsurface region. The adsorption isotherms for Cd2+ confirmed that the presence of SEP and AAS decreased the agglomeration of the nZVI particles in comparison to the pure nZVI, which provided a higher adsorption capacity. The results showed that the prevention of both aggregation and oxidation during the synthesis was necessary for obtaining an SEP/AAS-nZVI composite with a high adsorption capacity, but oxidation during adsorption was beneficial for Cd2+ removal. The formation of strong bonds between Cd2+ and the adsorbents sites of different energy until monolayer formation was proposed according to modeling of the adsorption isotherms.

Solidified structure and leaching properties of metallurgical wastewater treatment sludge after solidification/stabilization process.

The presented study investigates solidification/stabilization process of hazardous heavy metals/arsenic sludge, generated after the treatment of the wastewater from a primary copper smelter. Fly ash and fly ash with addition of hydrated lime and Portland composite cement were studied as potential binders. The effectiveness of the process was evaluated by unconfined compressive strength (UCS) testing, leaching tests (EN 12457-4 and TCLP) and acid neutralization capacity (ANC) test. It was found that introduction of cement into the systems increased the UCS, led to reduced leaching of Cu, Ni and Zn, but had a negative effect on the ANC. Gradual addition of lime resulted in decreased UCS, significant reduction of metals leaching and high ANC, due to the excess of lime that remained unreacted in pozzolanic reaction. Stabilization of more than 99% of heavy metals and 90% of arsenic has been achieved. All the samples had UCS above required value for safe disposal. In addition to standard leaching tests, solidificates were exposed to atmospheric conditions during one year in order to determine the actual leaching level of metals in real environment. It can be concluded that the EN 12457-4 test is more similar to the real environmental conditions, while the TCLP test highly exaggerates the leaching of metals. The paper also presents results of differential acid neutralization (d-AN) analysis compared with mineralogical study done by scanning electron microscopy and X-ray diffraction analysis. The d-AN coupled with Eh-pH (Pourbaix) diagrams were proven to be a new effective method for analysis of amorphous solidified structure.

Mixed-ligand MnII and CuII complexes with alternating 2,2'-bipyrimidine and terephthalate bridges.

The novel polymeric complexes catena-poly[[diaquamanganese(II)]-µ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')-[diaquamanganese(II)]-bis(µ-terephthalato-κ(2)O(1):O(4))], [Mn2(C8H4O4)2(C8H6N4)(H2O)4]n, (I), and catena-poly[[[aquacopper(II)]-µ-aqua-µ-hydroxido-µ-terephthalato-κ(2)O(1):O(1')-copper(II)-µ-aqua-µ-hydroxido-µ-terephthalato-κ(2)O(1):O(1')-[aquacopper(II)]-µ-2,2'-bipyrimidine-κ(4)N(1),N(1'):N(3),N(3')] tetrahydrate], {[Cu3(C8H4O4)2(OH)2(C8H6N4)(H2O)4]·4H2O}n, (II), containing bridging 2,2'-bipyrimidine (bpym) ligands coordinated as bis-chelates, have been prepared via a ligand-exchange reaction. In both cases, quite unusual coordination modes of the terephthalate (tpht(2-)) anions were found. In (I), two tpht(2-) anions acting as bis-monodentate ligands bridge the Mn(II) centres in a parallel fashion. In (II), the tpht(2-) anions act as endo-bridges and connect two Cu(II) centres in combination with additional aqua and hydroxide bridges. In this way, the binuclear [Mn2(tpht)2(bpym)(H2O)4] entity in (I) and the trinuclear [Cu3(tpht)2(OH)2(bpym)(H2O)4]·4H2O coordination entity in (II) build up one-dimensional polymeric chains along the b axis. In (I), the Mn(II) cation lies on a twofold axis, whereas the four central C atoms of the bpym ligand are located on a mirror plane. In (II), the central Cu(II) cation is also on a special position (site symmetry -1). In the crystal structures, the packing of the chains is further strengthened by a system of hydrogen bonds [in both (I) and (II)] and weak face-to-face π-π interactions [in (I)], forming three-dimensional metal-organic frameworks. The Mn(II) cation in (I) has a trigonally deformed octahedral geometry, whereas the Cu(II) cations in (II) are in distorted octahedral environments. The Cu(II) polyhedra are inclined relative to each other and share common edges.

Dirubidium hexaaquacobalt(II) tetrakis(hydrogen phthalate) tetrahydrate and coordination modes of the hydrogen phthalate anion.

The title compound, Rb2[Co(H2O)6](C8H5O4)4·4H2O, consists of nearly regular octahedral [Co(H2O)6]²âº cations with the CoII cations on the inversion centre (special position 2a), Rb⁺ cations, hydrogen phthalate (Hpht⁻) anions and disordered water molecules. The Rb⁺ cation is surrounded by nine O atoms from Hpht⁻ anions and water molecules, with a strongly deformed pentagonal-bipyramidal geometry and one apex split into three positions. The crystal packing is governed by numerous hydrogen bonds involving all water molecules and Hpht⁻) anions. In this way, layers parallel to the ab plane are formed, with the aromatic rings of the Hpht⁻ anions esentially directed along the c axis. While Hpht⁻ anions form the outer part of the layers, disordered water molecules and Rb⁺ cations alternate with [Co(H2O)6]²âº cations in the inner parts. The only interactions between the layers are van der Waals forces between the atoms of the aromatic rings. A search of the Cambridge Structural Database for coordination modes and types of hydrogen-bonding interaction of the Hpht⁻ anion showed that, when uncoordinated Hpht⁻ anions are present, compounds with intermolecular hydrogen bonds are more numerous than compounds with intramolecular hydrogen bonds. For coordinated Hpht⁻ anions, chelating and bridging anions are almost equally common, while monodentate anions are relatively scarce. The same coordination modes appear for Hpht⁻ anions with or without intramolecular hydrogen bonds, although intramolecular hydrogen bonds are less common.

Synthesis, characterization and antiproliferative activity of transition metal complexes with 3-(4,5-diphenyl-1,3-oxazol-2-yl)propanoic acid (oxaprozin).

A series of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with oxaprozin (Hoxa), a non-steroidal anti-inflammatory drug, has been synthesized. The drug and complexes have been characterized by elemental and thermogravimetric (TG) analysis, Fourier transform (FT)-IR, 1H-NMR, 13C-NMR, UV-Vis spectroscopy and magnetic susceptibility measurements. The (pseudo)octahedral geometry has been proposed for all complexes based on electronic spectra and magnetic moments. With exception of the Cu(II) complex, where bridging bidentate mode of COO groups has been found, FT-IR spectra confirmed chelately coordinated COO groups in the other complexes. The general formula of the complexes is [M(H2O)2(oxa)2 ·χH2O, with χ=2 for M=Mn, Co and Ni and χ=1.5 for Zn. The binuclear Cu(II) complex, [Cu2(H2O)2(OH)(oxa)3]·2H2O, has strong Cu-Cu interactions of antiferromagnetic type. The complexes and Hoxa did not exhibit the cytotoxic effect to peritoneal macrophages. For the first time these complexes have been tested for their in vitro antiproliferative activity against human colon and breast cancer cell lines, HCT-116 and MDA-231, respectively. For all investigated compounds significant antiproliferative effects have been observed. Ni(II) complex has been shown to be a promising antiproliferative agent exerting excellent activity against HCT-116 even in nanomolar concentrations.

Comparison of structural, textural and thermal characteristics of pure and acid treated bentonites from Aleksinac and Petrovac (Serbia).

Bentonite samples collected from vicinity of Petrovac and Aleksinac were treated with different sulfuric acid molarities. Acid attack dissolved the octahedral sheets by interlayer and edge attack. The effects of the H(2)SO(4) acid caused an exchange of Al(3+), Fe(3+) and Mg(2+) with H(+) ions leading to a modification of the smectite crystalline structure. The Mg and Fe substitution in the octahedral sheets promoted the dispersion of corresponding layers and formation of amorphous silicon. The activated bentonites, after the treatment of sulfuric acid, exhibited a lower cation-exchange capacity (CEC) and significant increase of specific surface area from 6 to 387 m(2) g(-1) (bentonite from Petrovac) and from 11 to 306 m(2) g(-1) (bentonite from Aleksinac). The acid reaction caused a splitting of particles within the octahedral sheet which led to an increase in specific surface area and decrease in CEC in both bentonites.

catena-Poly[[[(di-2-pyridylamine-κ2N2,N2')copper(II)]-µ-benzene-1,3-dicarboxylato-κ3O1,O1':O3] monohydrate], a zigzag coordination polymer with strong π-π interactions.

The novel title coordination polymer, {[Cu(C(8)H(4)O(4))(C(10)H(9)N(3))]·H(2)O}(n), synthesized by the slow-diffusion method, takes the form of one-dimensional zigzag chains built up of Cu(II) cations linked by benzene-1,3-dicarboxylate (ipht) anions. An exceptional characteristic of this structure is that it belongs to a small group of metal-organic polymers where ipht is coordinated as a bridging tridentate ligand with monodentate and chelate coordination of individual carboxylate groups. The Cu(II) cation has a highly distorted square-pyramidal geometry formed by three O atoms from two ipht anions and two N atoms from a di-2-pyridylamine (dipya) ligand. The zigzag chains, which run along the b axis, further construct a three-dimensional metal-organic framework via strong face-to-face π-π interactions and hydrogen bonds. A solvent water molecule is linked to the different carboxylate groups via hydrogen bonds. Thermogravimetric and differential scanning calorimetric analyses confirm the strong hydrogen bonding.

Comparison of two polymeric transition metal complexes with 1,4-benzenedicarboxylate ions as bridging ligands, [Co(C8H4O4)(C12H8N2)(H2O)] and [Cu(C8H4O4)(C10H9N3)].H2O.

The title complexes, catena-poly[[aqua(1,10-phenanthroline-kappa(2)N,N')cobalt(II)]-micro-benzene-1,4-dicarboxylato-kappa(2)O(1):O(4)], [Co(C(8)H(4)O(4))(C(12)H(8)N(2))(H(2)O)], (I), and catena-poly[[[(di-2-pyridyl-kappaN-amine)copper(II)]-micro-benzene-1,4-dicarboxylato-kappa(4)O(1),O(1'):O(4),O(4')] hydrate], [Cu(C(8)H(4)O(4))(C(10)H(9)N(3))].H(2)O, (II), take the form of zigzag chains, with the 1,4-benzenedicarboxylate ion acting as an amphimonodentate ligand in (I) and a bis-bidentate ligand in (II). The Co(II) ion in (I) is five-coordinate and has a distorted trigonal-bipyramidal geometry. The Cu(II) ion in (II) is in a very distorted octahedral 4+2 environment, with the octahedron elongated along the trans O-Cu-O bonds and with a trans O-Cu-O angle of only 137.22 (8) degrees.