Bis-8-hydroxyquinoline-armed diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands: possible fluorophoric metal ion sensors.

The synthesis and preliminary photophysical properties of a series of diazatrithia-15-crown-5 and diazatrithia-16-crown-5 ligands containing two 8-hydroxyquinoline sidearms are reported. The ligands were prepared by a two-step process. First, diazatrithiacrown ethers 11 and 12 were prepared by treating bis(alpha-chloroamide) 5 with various dimercaptans followed by reduction using a boron-THF complex. Hydroxymethyl-substituted macrocycle 12 was rearranged to hydroxy-substituted diazatrithia-16-crown-5 in refluxing aqueous HCl. Macrocyclic diamines 11-13 were converted to either 5-chloro-8-hydroxyquinolin-7-ylmethyl-substituted diazatrithiacrown ethers 14-16 by a Mannich aminomethylation reaction or to 8-hydroxyquinolin-2-ylmethyl-substituted diazatrithiacrown ethers 17-19 by reductive amination using 8-hydroxyquinoline-2-carboxaldehyde. Preliminary photophysical studies show that ligands 16 and 19 exhibit increased fluorescence in the presence of Zn(2+), indicating that these ligands could be chemical sensors for Zn(2+).     

Binding properties of octaaminocryptands

Complexation and protonation equilibria were studied in aqueous solution for a new range of aminocryptand ligands, N(CH2CH2NHCH2RCH2NHCH2CH2)3N, (R = m-xylyl, p-xylyl, 2,5-furan, 2,6-pyridine) and demonstrate that stability constants for first transition series ions Co2+ to Zn2+ are relatively high. X-ray crystallography shows that the cryptands are reasonably well preorganized for complexation. The furan-spaced cryptand L6.H2O crystallizes in the rhomobohedral space group R3 (no. 148) with a = 14.645(1), b = 14.645(1), and c = 25.530(4) A, whereas the m-xylyl-spaced cryptand L4 crystallizes in the triclinic space group P1 (no. 2) with a = 9.517(1), b = 15.584(2), and c = 23.617(4) A. The highest formation constant (log beta21 = 33.07) is observed for the dicopper cryptate of a pyridine-spaced cryptand, suggesting involvement in complexation of donors from the spacer link. This pyridine-spaced host also shows good selectivity for copper(II) over zinc(II), making it a possible candidate for treatment of copper-excess pathology.     

New Calix[4]arene-monobenzo- and -dibenzo-crown-6 as Cesium Selective Ionophores in the Radioactive Waste Treatment: Synthesis, Complexation and Extraction Properties

Cesium possesses two long lived isotopes ¹³⁵Cs and ¹³⁷Cs and the first one has a very long (2.3 × 10⁶ y) half life and is one of the most mobile nuclides in a repository.Calix[4]arene-crowns-6 in the 1,3-alternate conformation areemerging as a new class of ionophores exhibiting a very high efficiency and selectivity in the complexation of cesium ion and itsremoval from highly acidic ([HNO₃] = 3–4 M) radioactive waste having also high sodium nitrate concentration ([NaNO₃] = 2–4 M). In order to improve both efficiency and cesium selectivity we have synthesised the novel calix[4]arene dibenzo-crowns-6 1 and 2 and thecalix[4]arene-monobenzocrown-6 3 in 1,3-alternate conformationand evaluated their complexation properties towards alkali metal cations in homogeneous solution and in two phase systems, togetherwith their performance in radioactive waste treatment. All data confirm the higher Cs/Na selectivity of the 1,3-alternate calix[4]crown-6 1–3 containing aromatic rings in the polyether loop, in comparison to previously synthesised compounds of the same series.     

Novel C3v-symmetrical N7-Hexahomotriazacalix[3]cryptand: a highly efficient receptor for halide anions

[structure: see text] We report the synthesis of a novel C(3)(v)()-symmetrical N(7)-hexahomotriazacalix[3]cryptand (1). Compound 1 was shown to be in a fixed cone conformation by (1)H NMR spectroscopy and X-ray single-crystal structure determination. Complexation studies showed that 1 is a selective receptor for halide ions. The effects of zinc metal cation on the receptor (1-Zn(2+)) upon anion recognition are also shown.     

Complexing Properties of Phenolic Diazacrown Ethers with Transition and Heavy Metal Ions

The complexation equilibria of the phenolic diazacrown ether derivatives L1–L11 with transition and heavy metal ions (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺ and Pb²⁺) have been studied in methanol using UV absorption spectrophotometry. A majority of the systems studied formed only ML complexes. Using a ligand with a different position of the substituents on the phenolic side arms (denoted L7) leads to ML₂ formation with most of the metal ions. Every ligand forms very strong ML and ML₂ complexes with Pb²⁺, and, in nearly all cases, only a lower limit could be derived for the stability constant. The stability of the complexes generally increases as the length of the para-substituents on the phenol groups increases. Among the metal ions tested, Zn²⁺ and Hg²⁺ are the least preferred by alkyl and alkoxy derivatives, respectively.