Two multidentate ligands utilizing triazolyl, pyridinyl and phenolate groups as donors for constructing dinuclear copper(II) and iron(III) complexes: Syntheses, structures, and electrochemistry

Magnetostructural Properties of Some Doubly-Bridged Phenoxido Copper(II) Complexes

Three new tripod tetradentate phenolate-amines (H2L1, H2L4 and H2L9), together with seven more already related published ligands, were synthesized, and characterized. With these ligands, two new dinuclear doubly-bridged-phenoxido copper(II) complexes (3, 4), and six more complexes (1, 2, 5-8), a new trinuclear complex (9) with an alternative doubly-bridged-phenoxido and -methoxido, as well as the 1D polymer (10) were synthesized, and their molecular structures were characterized by spectroscopic methods and X-ray single crystal crystallography. The Cu(II) centers in these complexes exhibit distorted square-pyramidal arrangement in 1-4, mixed square pyramidal and square planar in 5, 6, and 9, and distorted octahedral (5+1) arrangements in 7 and 8. The temperature dependence magnetic susceptibility study over the temperature range 2-300 K revealed moderate-relatively strong antiferromagnetic coupling (AF) (|J| = 289-145 cm-1) in complexes 1-6, weak-moderate AF (|J| = 59 cm-1) in the trinuclear complex 9, but weak AF interactions (|J| = 3.6 & 4.6 cm-1) were obtained in 7 and 8. No correlation was found between the exchange coupling J and the geometrical structural parameters of the four-membered Cu2O2 rings.

Synthesis of a New Polyanion Possessing Dense 1,2,3-Triazole Backbone

Polyanions are an important class of water-soluble polymers because polyanions are utilized in a wide range of industrial fields. It is thus a great challenge to develop polyanions with novel structures to make their applications broader. In this study, a new polyanion with a dense 1,2,3-triazole backbone, poly(4-azido-5-hexanoic acid) (poly(AH)), was synthesized by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) polymerization of t-butyl 4-azido-5-hexanoate followed by hydrolysis of the t-butyl ester groups. Turbidimetric and potentiometric titration data indicated that poly(AH) was well soluble in water under basic conditions (pH < 7) and a weaker polyanion (apparent pKa = 5.4) than polyacrylic acid (apparent pKa = 4.5). Adsorption tests exhibited that sodium salt of poly(AH) (poly(AH)Na) adsorbed most preferably Fe3+ among the four metal ions examined, i.e., Cu2+, Pb2+, Li+, and Fe3+. 1H spin-lattice relaxation time measurements indicated that Fe3+ ions were adsorbed favorably onto the 1,2,3-triazole residues.

Hybrid Pyrazolyl-1,2,3-Triazolyl Tripodal Tetraamine Ligands: Click Synthesis and Cobalt(III) Complexes

A family of tripodal tetraamine ligands incorporating two pyrazolyl and one 1,2,3-triazolyl donor arm have been synthesized in modest-to-excellent yields (42–90 %) using the copper(i)-catalyzed azide–alkyne cycloaddition (CuAAC) reaction. Mono-, bis-, and tris-tripodal ligand scaffolds were readily generated using this method. The coordination chemistry of the ligands with cobalt(iii) ions has been studied, and cobalt(iii) carbonato complexes of the ligands have been isolated and characterized spectroscopically and crystallographically. X-ray crystallography and NMR spectroscopy of the mono-metallic complexes showed that racemic mixtures of the cis-isomer are formed selectively. The di- and tri-metallic systems could not be crystallized, but NMR spectroscopy indicates that these compounds were isolated as mixtures of stereoisomers.