Crystal structure and properties of a Cu(II) complex with the tridentate Schiff-base ligand, paeonol-(2-aminoethylpiperazine)

A new 1,8-naphthalimide-based fluorescent “turn-off” sensor for detecting Cu2+ and sensing mechanisms

In this article, a new “turn-off” fluorescent sensor N- n-butyl-4-{2-[(ethylimino)methyl]phenol}-1,8-naphthalimide (HL) for CuII ions is synthesized, which contains a 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. As expected, it exhibits high selectivity and sensitivity for detecting CuII ions over other common metal ions in acetonitrile–2-(4-(2-hydroxyethyl)-1-piperazinyl)-ethanesulfonic acid (HEPES) (1:1 v/v, pH = 7.4) solution. In addition, the fluorescence intensity for HL showed a good linearity with the concentration of CuII ions in the range of 0.5–5.0 μM. The 2:1 binding stoichiometry between HL and CuII ions was established on the basis of combined fluorescence titrations, a Job’s plot, single-crystal X-ray analysis and mass spectrometry. The quenching response of HL toward CuII ions is attributed to the reverse photoinduced electron transfer mechanism. The proposed sensor HL is preliminarily applied to quantify CuII ions in water samples from the Yellow River and tap water.

Tetradentate iminophenolate copper complexes in rac-lactide polymerization

Copper(II) nitrate complexes of 2-(((2-((2-aminoethyl)amino)ethyl)imino)methyl)phenol, 2-(((2-((2-aminoethyl)amino)ethyl)imino)methyl)-4,6-dichlorophenol, 2-(((2-(piperazin-1-yl)ethyl)imino)methyl)phenol and (2,4-di-tert-butyl-6-(((2-(piperazin-1-yl)ethyl)imino)methyl)phenol, as well as a copper(II) acetate complex of 2-(((2-(piperidin-1-yl)ethyl)imino)methyl)phenol, have been prepared and characterized by X-ray diffraction studies. In combination with benzyl alcohol, all complexes are active in rac-lactide polymerization at 140 °C in molten monomer to provide moderately heterotactic polylactic acid. Most complexes showed complicated reaction kinetics, indicative of two interconverting active species. Molecular weight control was poor and a strong tendency toward intramolecular transesterification led to oligomeric products. There was no indication that the basic site of the ligand is participating in the polymerization reaction by deprotonation of the alcohol nucleophile.

A family of ligand and anion dependent structurally diverse Cu(ii) Schiff-base complexes and their catalytic efficacy in an O-arylation reaction in ethanolic media

Catalytic O-arylation reactions have been studied by employing a variety of copper(ii) Schiff-base complexes under environmentally benign conditions.

Dichlorido(4-meth-oxy-2-{[2-(piperazin-4-ium-1-yl)eth-yl]imino-meth-yl}phenol-ate)cadmium

In the title compound, [CdCl₂(C₁₄H₂₁N₃O₂)], the Schiff base ligand chelates the Cd^II ion in an N,N,O-tridentate fashion. Two Cl atoms complete a distorted square-pyramidal coordination environment around the metal atom. In the crystal, adjacent mol­ecules are linked through C—H⋯π inter­actions into infinite chains along the a axis. The mol­ecules are further connected into a three-dimensional network via N—H⋯O, N—H⋯Cl and C—H⋯Cl inter­actions. The ethyl­ene group is disordered over two sets of sites in a 0.520 (10):0.480 (10) ratio.

Dichlorido(2-{[2-(piperazin-4-ium-1-yl)eth-yl]imino-meth-yl}phenolate)cadmium(II)

In the title compound, [CdCl₂(C₁₃H₁₉N₃O)], the Cd^II ion is penta­coordinated with the N,N,O-tridentate Schiff base 2-{[2-(piperazin-4-ium-1-yl)eth­yl]imino­meth­yl}phenolate ligand and two Cl atoms in a highly distorted square-pyramidal geometry; the piperazine ring adopts a chair conformation. In the crystal structure, adjacent mol­ecules are linked together via N—H⋯O and N—H⋯Cl hydrogen bonds, forming infinite layers parallel to the ab plane. The layers are further connected through C—H⋯Cl inter­actions into a three-dimensional network.