In the title compound, [Fe(C(34)H(29)O(2)P(2))](2)[Sb(2)Cl(8)], the discrete centrosymmetric [Sb(2)Cl(8)]2- anions are formed from two edge-shared square pyramids of Cl atoms about each Sb atom. Within the cation, the two diphenylphosphinate groups share one H atom and the ferrocene cyclopentadienyl rings are in a staggered conformation, with the average value of the twist angle being 46 degrees. In the crystal, each [Sb(2)Cl(8)]2- anion is involved in eight C-H* * *Cl interactions with four surrounding cations and these interactions interconnect the ions to form molecular columns along the a direction.
Two new applications for sequence treatment of mature (stabilized) landfill leachate, that is, cationic resin followed by anionic resin (cationic/anionic) and anionic resin followed by cationic resin (anionic/cationic), are employed and documented for the first time in the literature. Response surface methodology (RSM) concerning central composite design (CCD) is used to optimize each treatment process, as well as evaluate the individual and interactive effects of operational cationic resin dosage and anionic resin dosage on the effectiveness of each application in terms of color, chemical oxygen demand (COD), and NH(3)-N removal efficiency. A statistically significant model for color, COD, and NH(3)-N removal was obtained with high coefficient of determination values (R(2)>0.8). Under optimum operational conditions, the removal efficiency levels for color, COD, and NH(3)-N are 96.8%, 87.9%, and 93.8% via cationic/anionic sequence, and 91.6%, 72.3%, and 92.5% via anionic/cationic sequence, respectively. The experimental results and the model predictions agree well with each other.
In the title complex, the 1:1 ionic adduct of hexamethylenetetraminium and 2,4,6-trinitrophenolate, C6H13N4+*C6H2N3O7-, the cation acts as a donor for bifurcated hydrogen bonds to the O atoms of the phenolate and one of the nitro groups of the 2,4,6-trinitrophenolate anion. The crystal structure is built from sheets of cations and anions, and is stabilized by intermolecular C-H...O and C-H...pi interactions.
A kinetic study on the aqueous cleavage of N-(2-methoxyphenyl)phthalimide (1) and N-(2-hydroxyphenyl)phthalimide (2), under the buffers of N-methylmorpholine, reveals the equilibrium presence of monocationic amide (Ctam) formed due to nucleophilic reactions of N-methylmorpholine with 1 and 2. Pseudo-first-order rate constants for the reactions of water and HO- with Ctam (formed through nucleophilic reaction of N-methylmorpholine with 1) are 4.60 x 10(-5) s-1 and 47.9 M-1 s-1, respectively. But the cleavage of Ctam, formed through nucleophilic reaction of N-methylmorpholine with 2, involves intramolecular general base (2'-O- group of Ctam)-assisted water attack at carbonyl carbon of cationic amide group of Ctam in or before the rate-determining step.
In the title salt, C14H18N2(2+) · 2C9H5N4O(-), the 1,1'-diethyl-4,4'-bipyridine-1,1'-diium dication lies across a centre of inversion in the space group P21/c. In the 1,1,3,3-tetracyano-2-ethoxypropenide anion, the two independent -C(CN)2 units are rotated, in conrotatory fashion, out of the plane of the central propenide unit, making dihedral angles with the central unit of 16.0(2) and 23.0(2)°. The ionic components are linked by C-H...N hydrogen bonds to form a complex sheet structure, within which each cation acts as a sixfold donor of hydrogen bonds and each anion acts as a threefold acceptor of hydrogen bonds.
In the present work, complexes of DNA with nano-clay montmorillonite (Mt) were investigated by means of atomic force microscopy (AFM) under various conditions. In contrast to the integral methods of analysis of the sorption of DNA on clay, AFM allowed us to study this process at the molecular level in detail. DNA molecules in the deionized water were shown to form a 2D fiber network weakly bound to both Mt and mica. The binding sites are mostly along Mt edges. The addition of Mg2+ cations led to the separation of DNA fibers into separate molecules, which bound mainly to the edge joints of the Mt particles according to our reactivity estimations. After the incubation of DNA with Mg2+, the DNA fibers were capable of wrapping around the Mt particles and were weakly bound to the Mt edge surfaces. The reversible sorption of nucleic acids onto the Mt surface allows it to be used for both RNA and DNA isolation for further reverse transcription and polymerase chain reaction (PCR). Our results show that the strongest binding sites for DNA are the edge joints of Mt particles.
A systematic study of the electrochemical oxidation of 1,2-diarylalkenes was carried out with the focus on detailed product studies and variation of product type as a function of aromatic substitution. A reinvestigation of the electrochemical oxidation of 4,4'-dimethoxystilbene under various conditions was first carried out, and all products formed were fully characterized and quantitated. This was followed by a systematic investigation of the effect of aromatic substitution on the nature and distribution of the products. The aromatic substituents were found to fall into three main categories, viz., substrates in which the nature and position of the aromatic substituents gave rise to essentially the same products as 4,4'-dimethoxystilbene, for example, tetraaryltetrahydrofurans, dehydrotetralins, and aldehydes (p-MeO or p-NMe2 on one ring and X on the other ring, where X = o-MeO or p-alkyl, or m- or p-EWG; e.g., 4-methoxy-4'-trifluoromethylstilbene); those that gave rise to a mixture of indanyl (or tetralinyl) acetamides and dehydrotetralins (or pallidols) (both or one ring substituted by alkyl groups, e.g., 4,4'-dimethylstilbene); and those where strategic placement of donor groups, such as OMe and OH, led to the formation of ampelopsin F and pallidol-type carbon skeletons (e.g., 4,3',4'-trimethoxystilbene). Reaction pathways to rationalize the formation of the different products are presented.
Research and development in health care industry is in persistence progression. To make it more patient-friendly or to get maximum benefits from it, special attention to different advanced drug delivery system (ADDS) is employed that delivers the drug at the target site and will be able to sustain/control release of drugs. ADDS should be non-toxic, biodegradable, biocompatible along with desirable showing physicochemical and functional properties. These drug delivery systems can be totally based on polymers, either with natural or synthetic polymers. The molecular weight of polymer can be tuned and different groups of polymers can be modified or substituted with other functional groups. Degree of substitution is also tailored. Cationic starch in recent years is exploited in drug delivery, tissue engineering and biomedicine. Due to their abundant availability, low cost, easy chemical modification, low toxicity, biodegradability and biocompatibility, extensive research is now being carried out. Our present discussion will shed light on the usage of cationic starch in health care system.
In the title compound, [Fe(C(17)H(14)P)(2)](2)[Sb(4)Cl(16)] x C(2)H(6)O, the Fe atoms lie on inversion centres and the pairs of cyclopentadienyl rings are consequently in a fully staggered conformation. The centrosymmetric anionic clusters formed by [Sb(4)Cl(16)](4-) are surrounded by the cations and are held together by weak C-H...Cl interactions. These formations stack along the a axis to form columns, and the columns are interconnected by another weak C-H...Cl interaction along the b axis.
In the title ternary complex, C(10)H(9)N(2)(+).C(7)H(3)N(2)O(6)(-).C(7)H(4)N(2)O(6), the pyridinium cation adopts the role of the donor in an intermolecular N-H.O hydrogen-bonding interaction with the carboxylate group of the 3,5-dinitrobenzoate anion. The molecules of the ternary complex form molecular ribbons perpendicular to the b direction, which are stabilized by one N-H.O, one O-H.O and five C-H.O intermolecular hydrogen bonds. The ribbons are further interconnected by three intermolecular C-H.O hydrogen bonds into a three-dimensional network.
A sample of hydronium perchlorate, H(3)O(+) x ClO(4)(-), crystallized from ethanol at ambient temperature, was found to be orthorhombic (space group Pnma) at both 193 and 293 K, with no phase transition observed in this temperature range. This contrasts with the earlier observation [Nordman (1962). Acta Cryst. 15, 18-23] of a monoclinic phase (space group P2(1)/n) at 193 K for crystals grown at that temperature from perchloric acid. The hydronium and perchlorate ions lie across a mirror plane but it is not possible to define at either temperature a simple description of the H-atom positions due to the three-dimensional tumbling of the hydronium cation.
The crystal and mol-ecular structures of the title salt, C8H8N3S2 (+)·Cl(-), (I), and salt hydrate, C8H7ClN3S2 (+)·Cl(-)·H2O, (II), are described. The heterocyclic ring in (I) is statistically planar and forms a dihedral angle of 9.05 (12)° with the pendant phenyl ring. The comparable angle in (II) is 15.60 (12)°, indicating a greater twist in this cation. An evaluation of the bond lengths in the H2N-C-N-C-N sequence of each cation indicates significant delocalization of π-electron density over these atoms. The common feature of the crystal packing in (I) and (II) is the formation of charge-assisted amino-N-H⋯Cl(-) hydrogen bonds, leading to helical chains in (I) and zigzag chains in (II). In (I), these are linked by chains mediated by charge-assisted iminium-N(+)-H⋯Cl(-) hydrogen bonds into a three-dimensional architecture. In (II), the chains are linked into a layer by charge-assisted water-O-H⋯Cl(-) and water-O-H⋯O(water) hydrogen bonds with charge-assisted iminium-N(+)-H⋯O(water) hydrogen bonds providing the connections between the layers to generate the three-dimensional packing. In (II), the chloride anion and water mol-ecules are resolved into two proximate sites with the major component being present with a site occupancy factor of 0.9327 (18).
In the redetermination of the title compound, C3H5N2OS+·CI-, the asymmetric unit consists of one independent 2-oxo-1,3-thia-zolidin-4-iminium cation and one independent chloride anion. The cation inter-acts with a chloride anion via N-H⋯Cl hydrogen bonds forming a supra-molecular chain along [010]. These supra-molecular chains are further extended by weak C-H⋯Cl and C-H⋯O inter-actions, forming a two-dimensional network parallel to (001). The crystal structure is further stabilized by weak C-O⋯π inter-actions, supporting a three-dimensional architecture. The structure was previously determined by Ananthamurthy & Murthy [Z. Kristallogr. (1975). 8, 356-367] but has been redetermined with higher precision to allow the hydrogen-bonding patterns and supra-molecular inter-actions to be investigated.
The asymmetric unit of the title compound, [Co(C2H6N5)2(H2O)4][Co(C7H3NO4)2]2·2H2O, features 1.5 Co(II) ions (one anionic complex and one half cationic complex) and one water mol-ecule. In the cationic complex, the Co(II) atom is located on an inversion centre and is coordinated by two triazolium cations and four water mol-ecules, adopting an octa-hedral geometry where the N atoms of the two triazolium cations occupy the axial positions and the O atoms of the four water mol-ecules the equatorial positions. The two triazole ligands are parallel offset (with a distance of 1.38 Å between their planes). In the anionic complex, the Co(II) ion is six-coordinated by two N and four O atoms of the two pyridine-2,6-di-carboxyl-ate anions, exhibiting a slightly distorted octa-hedral coordination geometry in which the mean plane of the two pyridine-2,6-di-carboxyl-ate anions are almost perpendicular to each other, making a dihedral angle of 85.87 (2)°. In the crystal, mol-ecules are linked into a three-dimensional network via C-H⋯O, C-H⋯N, O-H⋯O and N-H⋯O hydrogen bonds.
This paper demonstrates an erbium/ytterbium co-doped fi bre amplifi er (EYDFA) which used a pumping wavelength of 1058 nm, whereby the amplifi cation was assisted by the energy transfer between Yb and Er ions. The energy transfer increased the erbium doping concentration limit that was imposed by concentration quenching in erbium-doped fi bre. The optimum length was obtained at 4m~6m for erbium/ytterbium co-doped fi bre with Er ion concentration of 1000 p.p.m. This enabled the development of a compact amplifi er with a shorter gain medium compared to erbium-doped fi bre amplifi ers which use a gain medium of up to 15 m. A 1058 nm pumping wave-length was used for the EYDFA, as 1480 nm pumping resulted in severely degraded gain and noise fi gures because the energy transfer could not be achieved. The use of the optical isolator improved the small signal gain and noise fi gure by about 4.8 dB and 1.6 dB, respectively. Without the isolator, gain saturation and a noise fi gure penalty were observed due to the oscillating laser which was created at around 1534 nm by spurious refl ection. This showed that the usage of optical isolators was an important aspect to consider when designing an EYDFA.
Bandgap tuning of a mixed organic cation perovskite is demonstrated via chemical vapor deposition process. The optical and electrical properties of the mixed organic cation perovskite can be manipulated by varying the growth time. A slight shift of the absorption band to shorter wavelengths is demonstrated with increasing growth time, which results in the increment of the current density. Hence, based on the optimized growth time, our device exhibits an efficiency of 15.86% with negligible current hysteresis.
This study was carried out to elucidate the effect of three types of cation (K+, Ca2+ and Na+) at various concentrations on the gelling properties of untreated Eucheuma cottoni, with the ultimate aim to explore the possibility of utilizing the seaweed in its natural form as gelling agent. Results obtained suggest that E. cottonii also exhibited the dramatic cation specificity of k-carrageenan, in which the dependence of gel strength follows the order: K+ > Ca2+ > Na+. As expected, cations addition exerts adverse effect on the syneresis, water holding capacity and freeze-thaw stability of the seaweed gel. Water holding capcity of the gel is however independent of the increased concentrations of K+(p>0.05). Storage duration and storage temperature significantly (p<0.05) affect the syneresis and water holding capacity of the gel. Among the cations, K+ appears to be better in improving the gel properties of the seaweed.
Classified as a small island, Kapas Island experiences major problems especially in supplying freshwater where groundwater abstraction is the only way to meet the demand of drinking water and domestic use. Groundwater samples were collected from seven constructed boreholes to examine the hydrochemistry properties of major ions and in-situ parameters as these could provide a basis for future reference. The chemical composition showed strong and significant correlation for each studied parameter; an indication of the effect of environmental variables to the groundwater composition. The composition changed from Ca-rich to Na-rich are explained mostly by mixing and cation exchange processes. This study provided an input for water management at Kapas Island where groundwater is a crucial resource to maintain the hydrogeological balance of the island.
The mechanical strength of magnetic lumen loaded handsheets was reported to be lower than the unloaded handsheets. This effect is due to the deposition of filler inside the fiber lumen and some on the fibre surface which interfere with the fibre to fibre bonding. Hence, in order to improve the handsheets strength, cationic starch is used as a dry strength additive. In this study, mixed tropical hardwood pulps were used throughout the experiment. The magnetite particles were deposited in the fibre lumen via the lumen loading technique. The addition of cationic starch was found to increase the handsheet strength. However, it disturbed and influenced the location and distribution of the magnetic fillers. Some of the magnetite particles were observed to be displaced from the fiber lumen and pit apertures. The charges of the filler particles and cationic starch played an important role in producing charge repulsion and pulling effect which lead to filler dislocation.
2D perovskites is one of the proposed strategies to enhance the moisture resistance, since the larger organic cations can act as a natural barrier. Nevertheless, 2D perovskites hinder the charge transport in certain directions, reducing the solar cell power conversion efficiency. A nanostructured mixed-dimensionality approach is presented to overcome the charge transport limitation, obtaining power conversion efficiencies over 9%.