Polymeric copper(ii) and dimeric oxovanadium(v) complexes of amide-imine conjugate: bilirubin recognition and green catalysis

An exceptionally simple amide-imine conjugate, (E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)-4-methylbenzohydrazide (L), derived by the condensation of 4-methyl-benzoic acid hydrazide (PTA) with 4-(diethylamino)-2-hydroxybenzaldehyde was utilized to prepare a dimeric oxo-vanadium (V1) and a one-dimensional (1D) copper(ii) coordination polymer (C1). The structures of L, V1 and C1 were confirmed by single crystal X-ray diffraction analysis. The experimental results indicate that V1 is a promising green catalyst for the oxidation of sulfide, whereas C1 has potential for a C-S cross-coupling reaction in a greener way. Most importantly, C1 is an efficient 'turn-on' fluorescence sensor for bilirubin that functions via a ligand displacement approach. The displacement equilibrium constant is 7.78 × 105 M-1. The detection limit for bilirubin is 1.15 nM in aqueous chloroform (chloroform/water, 1/4, v/v, PBS buffer, and pH 8.0).

From solid state to in vitro anticancer activity of copper(II) compounds with electronically-modulated NNO Schiff base ligands

The copper(ii) complexes of general formula [Cu(GL)(Cl)] (1-3, G = OMe, H and NO2, respectively), bearing tridentate Schiff base ligands (GL-) and a chloride as a fourth labile one, are here reported. The Schiff bases derive from the monocondensation of ethylenediamine and substituted salicylaldehyde, where the electronic properties are modulated by the releasing or withdrawing power of the G group. The compounds were structurally characterized through single crystal Synchrotron X-ray diffraction experiments in the solid state, revealing that 1 (OMe) and 2 (H) adopt a dimeric assembly [Cu(μ-Cl)(GL)]2 through apical interaction of the chloride ions of two monomeric units, while 3 embraces a 1D polymeric chain structure [Cu(μ-Cl)(NO2L)]n with a similar bridging fashion, all supported by extended intramolecular or intrachain hydrogen bonds. The redox properties of the complexes were also studied by cyclic voltammetry with no marked effect of the substituent on the potential of the CuII/CuI redox system. UV/Vis spectroscopic studies in mimicked physiological conditions highlighted the intactness and stability of the coordinated NNO tridentate ligand in 1-3 and the lability of the coordinated chloride ion with the formation of the aquo-complexes [Cu(GL)(H2O)]+ in aqueous solution, as confirmed by conductance measurements with a 1 : 1 electrolyte molar conductivity. In vitro tests on cell viability were conducted on malignant cell lines typical for their poor prognosis and curability, revealing time-dependent and differential cytotoxicity given by the substituent G. All compounds were capable of formation of intracellular reactive oxygen species and DNA intercalation, acting as nuclease and producing double-strand DNA breaks. This is especially effective for 3 (NO2), which revealed the highest anticancer activity against malignant triple-negative breast cancer MDA-MB-231 cells, with a two-to-four-fold cytotoxicity enhancement with respect to 1 (OMe) and 2 (H), and, most important, substantial differentiation of cytotoxicity with respect to healthy endothelial HUVEC cell line.

Comment on "Mixed azido/phenoxido bridged trinuclear Cu(ii) complexes of Mannich bases: synthesis, structures, magnetic properties and catalytic oxidase activities", Dalton Trans., 2018, 47, 9385-9399 and "Tri- and hexa-nuclear NiII-MnII complexes of a N2O2 donor unsymmetrical ligand: synthesis, structures, magnetic properties and catalytic oxidase activities", Dalton Trans., 2018, 47, 13957-13971

This letter comments on two examples of numerical results of kinetic parameters which are inconsistent with the experimental data given in the same articles. Since this seems to be a trend in inorganic chemistry articles dealing with the catalytic oxidation of 3,5 di tert- butylcatechol and ortho-aminophenol, we call the attention of editors, reviewers and readers about grossly overestimated catalytic parameters in the literature.