Copper(II)–cerium(III) 15-metallacrown-5 based on glycinehydroxamic acid as a new precursor for heterobimetallic composite materials on carbon nanotubes

Morphology, Solid Structure and Antioxidant Activity in Vitro of Angelica sinensis Polysaccharide-Ce(IV)

Angelica Sinensis polysaccharide cerium (ASP-Ce) was prepared by Angelica Sinensis polysaccharide (ASP) and cerium ammonium nitrate (NH₄ )₂ Ce(NO₃ )₆ . and its morphology, and solid structure was investigated. The antioxidant activity of the ASP-Ce complex in vitro was evaluated. The antioxidant activity of ASP-Ce complex in vitro was evaluated by the scavenging activity of 2,2-diphenyl-1-picrylhyrazyl radical (DPPH), hydroxyl radical (⋅OH) and superoxide anion radical ( O 2 - ${{{\rm O}}_{2}^{-}}$ ⋅). The results showed that the ASP-Ce had the more ordered structure for inserting the Ce⁴⁺ into the polymer chain of ASP and there was little change in the conformation of the polysaccharide from Ce⁴⁺ . Three free radical scavenging experiments proved that ASP-Ce had better antioxidant capacity than of ASP, especially on DPPH, and then on O 2 - ${{{\rm O}}_{2}^{-}}$ ⋅. The scavenging rate of ASP-Ce at 1.0 mg/mL on DPPH reached 71.6 %. Therefore, these results provide references for the further development and utilization of rare earth-polysaccharide.

Crystal structure of a TbIII-CuII glycine-hydroxamate 15-metallacrown-5 sulfate complex

The core of the title complex, bis-[hexa-aqua-hemi-aqua-penta-kis-(μ3-glycine-hydroxamato)sulfato-penta-copper(II)terbium(III)] sulfate hexa-hydrate, [TbCu5(SO4)(GlyHA)5(H2O)6.5]2(SO4)·6H2O (1), which belongs to the 15-metalla-crown-5 family, consists of five glycine-hydroxamate dianions (GlyHA2-; C2H4N2O2) and five copper(II) ions linked together forming a metallamacrocyclic moiety. The terbium(III) ion is connected to the centre of the metallamacrocycle through five hydroxamate oxygen atoms. The coordination environment of the Tb3+ ion is completed to an octa-coordination level by oxygen atoms of a bidentate sulfate and an apically coordinated water mol-ecule, while the copper(II) atoms are square-planar, penta- or hexa-coordinate due to the apical coordination of water mol-ecules. Continuous shape calculations indicate that the coordination polyhedron of the Tb3+ ion in 1 is best described as square anti-prismatic. The positive charge of each pair of [TbCu5(GlyHA)5(H2O)6.5(SO4)]2 2+ fragments is compensated by a non-coordinated sulfate anion, which is located on an inversion center with 1:1 disordered oxygen atoms. Complex 1 is isomorphous with the previously reported compounds [LnCu5(GlyHA)5(SO4)(H2O)6.5]2(SO4), where Ln III = Pr, Nd, Sm, Eu, Gd, Dy and Ho.

The first water-soluble polynuclear metallamacrocyclic Sr(ii)-Cu(ii) complex based on simple glycinehydroximate ligands

Recently, aminohydroximate ligands have found wide applications in the fascinating class of polynuclear metallamacrocyclic compounds named 15-MC-5 metallacrowns. The enhanced interest in water-soluble aminohydroximate Ln(iii)-Cu(ii) complexes is largely due to their rich coordination chemistry, diverse properties and ease of synthesis. We examined glycinehydroxamic acid as a simple ligand for the preparation of the first water-soluble polynuclear metallamacrocyclic Sr(ii)-Cu(ii) compound. The complex Sr(H2O)3[15-MCCuGlyha-5](Cl)2 was synthesized and characterized structurally and spectroscopically. The single-crystal structure reveals the classic metallamacrocyclic 15-MC-5 configuration. The Sr(ii) ion is located at the center of the 15-MCCu(II)Glyha-5 ring and coordinated by five oxygen atoms of the cycle in the equatorial plane and an additional three oxygen atoms of the water molecules at apical positions. Detailed DFT and QT AIM studies were carried out for the hydrated isoelectronic Sr[15-MCCuGlyha-5]2+ and Y[15-MCCuGlyha-5]3+ systems. The ionic contribution to the metal-ligand interactions appears to be higher for the Sr(ii) derivative despite the smaller charge separation. DFT calculations suggest a thermodynamically favorable substitution of the Sr(ii) central ion with Y(iii). Indeed, it was shown experimentally that the strontium ion can be easily replaced by yttrium. Preliminary cytotoxic studies revealed the low toxicity of the strontium complex and its yttrium analogue, so the water-soluble Sr(ii) and Y(iii) metallacrowns can be further investigated as possible platforms for the development of new 90Sr and 90Y radiotherapy drugs.