Multiple defect-core hexagonal photonic crystal fiber with flattened dispersion and polarization maintaining properties

In this paper, we present a dispersion controlling technique with a multiple defect-core hexagonal photonic crystal fiber (MD-HPCF). By omitting air holes in the core region of the conventional HPCF and adjusting the size of air holes around the newly formed core, we can successfully design low flattened dispersion PCF with low confinement loss, as well as high birefringence. The low flattened dispersion feature, as well as the low confinement losses and high birefringence are the main advantages of the proposed PCF structure, making it suitable as chromatic dispersion controller, dispersion compensator, and/or polarization maintaining fiber.     

The electronic structure of the isoelectronic, square-planar complexes [FeII(L)2]2- and [CoIII(L Bu)2]- (L2- and (L Bu)2-=benzene-1,2-dithiolates): an experimental and density functional theoretical study

The electronic structures of two formally isoelectronic transition-metal dithiolato complexes [Fe(L)2]2- (1) and [Co(L Bu)2]1- (2) both possessing a spin triplet ground state (St=1) have been investigated by various spectroscopic and density functional methods; H2L Bu represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol and H2L is the corresponding unsubstituted benzene-1,2-dithiol. An axial zero-field splitting (D) of +32 cm(-1) for 2 has been measured independently by SQUID magnetometry, far-infrared absorption, and variable-temperature and variable-field (VTVH) magnetic circular dichroism spectroscopies. A similar D value of +28 cm(-1) is obtained for 1 on the basis of VTVH SQUID measurements. The absorption spectra of 1 and 2 are found, however, to be very different. Complex 1 is light yellow in color with no intense transition in the visible region, whereas 2 is deep blue. DFT calculations establish that the electronic structures of the [Fe(L)2](2-) and [Co(L)2]1- anions are very different and explain the observed differences in their absorption spectra. On the basis of these spectroscopic and theoretical analyses, 1 is best described as containing an intermediate spin FeII ion, whereas for the corresponding cobalt complex, oxidation states describing a d6 (CoIII) or d7 (CoII) electron configuration cannot be unambiguously assigned. The physical origin of the large zero-field splitting in both 1 and 2 is found to be due to the presence of low-energy spin-conserved d-d excitations which lead to a large Dzz through efficient spin-orbit coupling. Differential covalency effects appear to be of limited importance for this property.     

Synthesis,Spectroscopic and Crystal Structure Analysis of <Emphasis Type="Italic">N</Emphasis>-[imidazolidin-2-ylidene]-5-(thien-2-yl)[1,3,4]thiadiazole-2-amine

The crystal structure of the title compound has been determined. The compound crystallizes in the monoclinic space group P2₁/c with a = 5.9885(2) Å, b = 14.7345(4) Å, c = 12.3719(4) Å, β = 96.655(5)°, V = 1084.31(8) Å³, z = 4. An intramolecular N–H···N hydrogen bond forms a pseudo-six-membered ring with graph set S ¹ ₁(6). The crystal structure is stabilized by intermolecular interactions of the type N–H···N and C–H···N. The packing motifs in accordance with Etter’s analysis are R ² ₂(8) corresponding to N–H···N dimer and that generated by the chain is C(7).     

Amide linkage in novel three-ring bent-core molecular assemblies: polar mesophases and importance of H-bonding

Here, we report the first examples of achiral unsymmetrical three-ring bent-shaped liquid crystals comprising amide and imine linkages with transverse substituents of methyl and chloro moieties on the central phenyl ring in the core, exhibiting polar banana phases. The extensive intra and inter molecular H-bonding induced novel banana mesomorphic phases. One-dimensional stacking in the mesomorphic phase as well as ferroelectric polar order promoted by intermolecular H-bonding of amide linkage is demonstrated. The compounds exhibit multifunctional properties viz., the enantiotropic liquid crystalline (LC) phase at ambient temperatures, electro-optical response, spontaneous polarisation, emission characteristics with large Stokes shift, and even charge distribution with large voltage holding ratio (VHR) values. The smectic type phase was confirmed by XRD studies and polar order was established by switching current and dielectric investigations. DFT studies revealed the importance of their suitability for display applications.     

Synthesis,photopolymerization, and adhesive properties of hydrolytically stable phosphonic acid‐containing (meth)acrylamides

Three novel dental monomers containing phosphonic acid groups ( 1a and 2a , based on diethyl amino(phenyl)methylphosphonate and 3a based on diethyl 1‐aminoheptylphosphonate) were synthesized in two steps: the reaction of α‐aminophosphonates with acryloyl chloride (for monomers 1a and 3a ) or methacryloyl chloride (for 2a ) to give monomers with phosphonate groups, and the hydrolysis of phosphonate groups by using trimethyl silylbromide. Their (and the intermediates') structures were confirmed by FTIR, ¹H, ¹³C, and ³¹P NMR spectroscopy. All the monomers dissolve well in water (1<pH<2) and are hydrolytically stable. Their homo‐ and copolymerizations with 2‐hydroxyethyl methacrylate (HEMA) and HEMA/glycerol dimethacrylate were investigated with photo‐DSC. Thermal polymerization of the new monomers in water or in ethanol/water solution was investigated, giving polymers in good yields. X‐ray diffraction results showed only dicalcium phosphate dehydrate formation upon interaction of 1a ‐ 3a with hydroxyapatite indicating its strong decalcification and that monomer‐Ca salts are highly soluble. Some results were also compared to those with a bisphosphonic acid‐containing methacrylamide ( 4a ) previously reported; and the influence of monomer structure on polymerization/adhesive properties is discussed. These properties, especially hydrolytic stability and good rates of polymerization, make these new monomers suitable candidates as components of dental adhesive mixtures. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 511–522     

Nickel(II) chloride hexahydrate catalyzed reaction of aromatic aldehydes with 2-mercaptoethanol: formation of supramolecular helical assemblage of the product

Various aromatic aldehydes on reaction with 2-mercaptoethanol provided an unanticipated product, bis(2-hydroxyethyl)dithioacetals (3) as the major product along with the expected product 1,3-oxathiolanes (4) in the presence of 0.05 equiv amount of nickel(II) chloride hexahydrate (NiCl₂·6H₂O) under solvent-free conditions. Products 3c and 3e exhibit an interesting hydrogen-bonded infinite supra-molecular helical structure.     

Mixed-ligand metal complexes containing an ONS Schiff base and imidazole/benzimidazole ligands: synthesis,characterization, crystallography and biological activity

Salicylaldehyde-4-methylthiosemicarbazone (H₂MTSali) has been prepared via the condensation reaction of 4-methyl-3-thiosemicarbazide and salicylaldehyde. Four new mixed-ligand copper(II) and nickel(II) complexes with a general formula [M(MTSali)L] (M = Cu²⁺ or Ni²⁺; L = co-ligand) were synthesized, where L is either imidazole (im) or benzimidazole (bzim). The Schiff base and its mixed-ligand complexes were characterized by IR and UV/Vis spectroscopy, and the complexes by molar conductivity and magnetic susceptibility measurements. The spectroscopic data indicated that the Schiff base behaves as a tridentate ONS donor ligand coordinating via the phenoxide-oxygen, azomethine-nitrogen, and thiolate-sulphur atoms. Magnetic data indicate a square planar environment for the nickel(II) complexes while molar conductance values indicate that the metal complexes are essentially non-electrolytes in DMSO solution. X-ray crystallography shows Cu(MTSali)bzim (1) and Ni(MTSali)bzim (3) to be isostructural, with the metal(II) ions being coordinated by a N₂OS donor set that defines an approximate square planar geometry; in both cases, the benzimidazole is splayed with respect to the coordination plane. The copper(II) complexes were active against MDA-MB-231 and MCF-7 breast cancer cell lines, more so than H₂MTSali, whereas the nickel(II) complexes were inactive.     

Density functional study on structures, stabilities, and electronic properties of size-selected Pd n Si q (n = 1–7 and q = 0, +1, −1) clusters

The density functional theory (DFT) calculations within the framework of generalized gradient approximation have been employed to systematically investigate the geometrical structures, stabilities, and electronic properties of Pd _n Si ^q (n = 1–7 and q = 0, +1, ?1) clusters and compared them with the pure ${\text{Pd}}_{n + 1}^{q}$ (n = 1–7 and q = 0, +1, ?1) clusters for illustrating the effect of doping Si atom into palladium nanoclusters. The most stable configurations adopt a three-dimensional structure for both pure and Si-doped palladium clusters at n = 3–7. As a result of doping, the Pd _n Si clusters adopt different geometries as compared to that of Pd _n+1. A careful analysis of the binding energies per atom, fragmentation energies, second-order difference of energies, and HOMO–LUMO energy gaps as a function of cluster size shows that the clusters ${\text{Pd}}_{4}^{ + }$ , ${\text{Pd}}_{4}$ , ${\text{Pd}}_{8}^{ - }$ , ${\text{Pd}}_{5} {\text{Si}}^{0, + , - }$ , and ${\text{Pd}}_{7} {\text{Si}}^{0, + , - }$ possess relatively higher stability. There is enhancement in the stabilities of palladium frameworks due to doping with an impurity atom. In addition, the charge transfer has been analyzed to understand the effect of doped atom and compared further.     

Preparation of CTA-based polymer inclusion membrane using calix[4]arene derivative as a carrier for Cr(VI) transport

In this work, the transport of Cr(VI) ions from an aqueous donor phase solution to an acceptor phase that contained an acetic acid/ammonium acetate buffer at pH 5 through a polymer inclusion membrane (PIM) containing p-tert-butylcalix[4]arene amine derivative as carrier was studied. The Cr(VI) passed through a PIM comprised of cellulose triacetate as a support and 2-NPOE as a plasticizer. The transport efficiency of Cr(VI) was studied under various experimental conditions, such as effect of carrier concentration, acceptor phase pH, type of plasticizer in the membrane, stirring rate and membrane thickness. The kinetic parameters were calculated as rate constant (k), permeability coefficient (P), and flux (J). The transport efficiency of Cr(VI) was observed to be 95.07 % after 10 h under optimized conditions. The prepared PIM was characterized with Fourier transform infrared spectroscopy and the atomic force microscopy techniques as well as with contact angle measurements. This is an effective method for the removal of Cr(VI) which is toxic for human body and environment from the waste water.