The double‐stranded ladder‐like structure of poly[[bis(μ2‐acetato‐κ2O:O′)bis(acetato‐κO)bis(μ‐4,4′‐bipyridine‐κ2N:N′)dicopper(II)] 4‐nitrophenol disolvate tetrahydrate]

The reaction of 4,4′‐bipyridine with copper acetate in the presence of 4‐nitrophenol led to the formation of the title compound, {[Cu(CH₃COO)₂(C₁₀H₈N₂)]·C₆H₅NO₃·2H₂O}_n. The complex forms a double‐stranded ladder‐like coordination polymer extending along the b axis. The double‐stranded polymers are separated by 4‐nitrophenol and water solvent molecules. The two Cu^II centres of the centrosymmetric Cu₂O₂ ladder rungs have square‐pyramidal coordination environments, which are formed by two acetate O atoms and two 4,4′‐bipyridine N atoms in the basal plane and another acetate O atom at the apex. The ladder‐like double strands are separated from each other by one unit‐cell length along the c axis, and are connected by the water and 4‐nitrophenol molecules through a series of O—H...O and C—H...O hydrogen‐bonding interactions and two unique intermolecular π–π interactions.     

Quinoline Functionalized Schiff Base Silver (I) Complexes: Interactions with Biomolecules and In Vitro Cytotoxicity,Antioxidant and Antimicrobial Activities

A series of fifteen silver (I) quinoline complexes Q1–Q15 have been synthesized and studied for their biological activities. Q1–Q15 were synthesized from the reactions of quinolinyl Schiff base derivatives L1–L5 (obtained by condensing 2-quinolinecarboxaldehyde with various aniline derivatives) with AgNO₃, AgClO₄ and AgCF₃SO₃. Q1–Q15 were characterized by various spectroscopic techniques and the structures of [Ag(L1)₂]NO₃ Q1, [Ag(L1)₂]ClO₄ Q6, [Ag(L2)₂]ClO₄ Q7, [Ag(L2)₂]CF₃SO₃ Q12 and [Ag(L4)₂]CF₃SO₃ Q14 were unequivocally determined by single crystal X-ray diffraction analysis. In vitro antimicrobial tests against Gram-positive and Gram-negative bacteria revealed the influence of structure and anion on the complexes′ moderate to excellent antibacterial activity. In vitro antioxidant activities of the complexes showed their good radical scavenging activity in ferric reducing antioxidant power (FRAP). Complexes with the fluorine substituent or the thiophene or benzothiazole moieties are more potent with IC₅₀ between 0.95 and 2.22 mg/mL than the standard used, ascorbic acid (2.68 mg/mL). The compounds showed a strong binding affinity with calf thymus-DNA via an intercalation mode and protein through a static quenching mechanism. Cytotoxicity activity was examined against three carcinoma cell lines (HELA, MDA-MB231, and SHSY5Y). [Ag(L2)₂]ClO₄ Q7 with a benzothiazole moiety and [Ag(L4)₂]ClO₄ Q9 with a methyl substituent had excellent cytotoxicity against HELA cells.     

CHARACTERIZATION OF BEST APPROXIMATIONS IN METRIC LINEAR SPACES

Let (X,d) be a real metric linear space, with translation-invariant metric d and G a linear subspace of X. In this paper we use functionals in the Lipschitz dual of X to characterize those elements of G which are best approximations to elements of X. We also give simultaneous characterization of elements of best approximation and also consider elements of ε-approximation.     

Functional inequalities and best approximation

We investigate the relationship between best approximations by elements of closed convex cones and the estimation of functionals on an inner product space (X, <⊙,⊙>) in terms of the inner product on X.     

Synthesis and structural elucidation of 1-D silver(I) aliphatic carboxylate coordination polymers with 1,3,5-triaza-7-phosphaadamantane/N-methyl-1,3,5-triaza-7-phosphaadamantane

Reactions of silver(I) salts of acetate and trifluoroacetate with 1,3,5-triaza-7-phosphaadamantane (PTA) afforded 1-D coordination polymers [Ag(μ₂-PTA-κ²P?-:N)(μ₂-O₂CCH₃-κ²O:O′)]_n·2nH₂O (1) and [Ag(μ₂-PTA-κ²P:N)(μ₂-O₂CCF₃-κO)]_n·nH₂O (2), while a reaction of silver(I)trifluoroacetate with N-methyl-1,3,5-triaza-7-phosphaadamantane (PTAMe) afforded the coordination polymer [Ag(PTAMe)(μ₃-O₂CCF₃-κ³O:O:O’)(μ₂-O₂CCF₃-κ²O:O′)]_n (3). The coordination polymers were characterized using single-crystal X-ray diffraction. Nuclear magnetic resonance, infrared, and electron spray ionization mass spectrometries were used to initially establish complexation of Ag(I) to the PTA or PTAMe before recrystallization. In the crystal structures of 1 and 2, coordination of the PTA moieties to Ag(I) is via P and N forming chains that are linked through bridging carboxylates. The resulting structural motif can be described as ladder-like in which –[PTA–Ag–PTA]– chains are the strands while the bridging carboxylates comprising of –[Ag–O–C–O]₂– or –[Ag–O]₂– metallacycle rungs of the ladder. Compound 3 forms single-stranded coil-like coordination polymers with two non-equivalent Ag(I) centers, both tetrahedrally coordinated by four oxygens from four trifluoroacetates in one and by three oxygens from the trifluoroacetates and in each by the P of the PTAMe with alternating Ag?Ag interactions. The crystal structures of all three coordination polymers have a variety of fairly strong hydrogen bonds and intermolecular interactions which contribute stabilization of the crystal lattices.     

Flexible Molecular Precursors for Selective Decomposition to Nickel Sulfide or Nickel Phosphide for Water Splitting and Supercapacitance

Herein, the synthesis of three nickel(II) dithiophosphonate complexes of the type [Ni{S₂P(OR)(4-C₆H₄OMe)}₂] [R=H ( 1 ), C₃H₇ ( 2 )] and [Ni{S₂P(OR)(4-C₆H₄OEt}₂] [R=(C₆H₅)₂CH ( 3 )] is described; their structures were confirmed by single-crystal X-ray studies. These complexes were subjected to surfactant/solvent reactions at 300 °C for one hour as flexible molecular precursors to prepare either nickel sulfide or nickel phosphide particles. The decomposition of complex 2 in tri-octylphosphine oxide/1-octadecene (TOPO/ODE), TOPO/tri-n-octylphosphine (TOP), hexadecylamine (HDA)/TOP, and HDA/ODE yielded hexagonal NiS, Ni₂P, Ni₅P₄, and rhombohedral NiS, respectively. Similarly, the decomposition of complex 1 in TOPO/TOP and HDA/TOP yielded hexagonal Ni₂P and Ni₅P₄, respectively, and that of complex 3 in similar solvents led to hexagonal Ni₅P₄, with TOP as the likely phosphorus provider. Hexagonal NiS was prepared from the solvent-less decomposition of complexes 1 and 2 at 400 °C. NiS (rhom) had the best specific supercapacitance of 2304 F g⁻¹ at a scan rate of 2 mV s⁻¹ followed by 1672 F g⁻¹ of Ni₂P (hex). Similarly, NiS (rhom) and Ni₂P (hex) showed the highest power and energy densities of 7.4 kW kg⁻¹ and 54.16 W kg⁻¹ as well as 6.3 kW kg⁻¹ and 44.7 W kg⁻¹, respectively. Ni₅P₄ (hex) had the lowest recorded overpotential of 350 mV at a current density of 50 mA cm⁻² among the samples tested for the oxygen evolution reaction (OER). NiS (hex) and Ni₅P₄ (hex) had the lowest overpotentials of 231 and 235 mV to achieve a current density of 50 mA cm⁻², respectively, in hydrogen evolution reaction (HER) examinations.     

Interhalogen 1,2,3-Triazolium Ionic Liquid: Synthesis,Crystal Structure,Hirshfeld Surface Analysis and Photophysical Properties

Journal of Chemical Crystallography - A new interhalogen ionic liquid [C17H25N3Br]+[IBr2]? (IL-1) was synthesized from its triazolium iodide precursor [C17H26N3+I?] in THF under cold...     

Best Interpolatory Approximation in Normed Linear Spaces

A theory of best approximation with interpolatory contraints from a finite-dimensional subspaceMof a normed linear spaceXis developed. In particular, to eachxX, best approximations are sought from a subsetM(x) ofMwhichdependson the elementxbeing approximated. It is shown that this “parametric approximation” problem can be essentially reduced to the “usual” one involving a certainfixedsubspaceM₀ofM. More detailed results can be obtained when (1) Xis a Hilbert space, or (2) Mis an “interpolating subspace” ofX(in the sense of [1]).     

Upper semicontinuity of parametric projections

In this paper we study upper semicontinuity of the metric projection P _(p)(x) with respect to (x, p), where x is a point in a normed linear space X and (p) is an approximatively compact subset of X depending on a parameter p. An application to parametric spline approximation is given.     

Weak Chebyshev Subspaces and Continuous Selections for Parametric Projections

We examine the existence of continuous selections for the parametric projection onto weak Chebyshev subspaces. In particular, we show that if is the class of polynomial splines of degree n with the k fixed knots then the parametric projection admits a continuous selection if and only if the number of knots does not exceed the degree of splines plus one. February 15, 1996. Date revised: September 16, 1996.