Synthesis, crystal structure, magnetic and electrochemical studies of two copper complexes with carboxylate rich dinucleating ligand

Exploring a new family of designer copper(II) complexes of anthracene-appended polyfunctional organic assembly displaying potential anticancer activity via cytochrome c mediated mitochondrial apoptotic pathway

The present article describes the systematic study on design and synthesis, physicochemical properties and spectroscopic features, and potential anticancer activities of a family of novel copper(II)-based designer metal complexes [Cu₂(acdp)(μ-Cl)(H₂O)₂] (1), [Cu₂(acdp)(μ-NO₃)(H₂O)₂] (2) and [Cu₂(acdp)(μ-O₂CCF₃)(H₂O)₂] (3) of anthracene-appended polyfunctional organic assembly, H₃acdp (H₃acdp = N,N'-bis[anthracene-2-ylmethyl]-N,N'-bis[carboxymethyl]-1,3-diaminopropan-2-ol). Synthesis of 1-3 was accomplished under facile experimental conditions, preserving their overall integrity in solution. The incorporation of polycyclic anthracene skeleton within the backbone of organic assembly increases lipophilicity of resulting complexes, thereby dictating the degree of cellular uptake with improved biological activity. Complexes 1-3 were characterized by elemental analysis, molar conductance, FTIR, UV-Vis absorption/fluorescence emission titration spectroscopy, PXRD and TGA/DTA studies, including DFT calculations. The cellular cytotoxicity of 1-3 when studied in HepG2 cancer cell line showed substantial cytotoxic effects, whereas no such cytotoxicity was observed when exposed to normal L6 skeletal muscle cell line. Thereafter, the signaling factors involved in the process of cytotoxicity in HepG2 cancer cells were investigated. Alteration of cytochrome c and Bcl-2 protein expression levels along with modulation of mitochondrial membrane potential (MMP) in the presence of 1-3, strongly suggested the possibility of activating mitochondria-mediated apoptotic pathway involved in halting the cancer cell propagation. However, when a comparative assessment on their bio-efficacies was made, 1 showed higher cytotoxicity, nuclear condensation, DNA binding and damage, ROS generation and lower rate of cell proliferation compared to 2 and 3 in HepG2 cell line, indicating that the anticancer activity of 1 is significantly higher than that of 2 and 3.

Ancillary-Ligand-Assisted Variation in Nuclearities Leading to the Formation of Di-, Tri-, and Tetranuclear Copper(II) Complexes with Multifaceted Carboxylate Coordination Chemistry

The self-assembly of a carboxylate-based dinucleating ligand, N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H₃cpdp), and copper(II) ions in the presence of various exogenous ancillary ligands results in the formation of the new dinuclear complex [Cu₂(cpdp)(μ-Hisophth)]₄·2H₂isophth·21H₂O (1), trinuclear complex [Cu₃(Hcpdp)(Cl)₄] (2), and tetranuclear complex [Cu₄(cpdp)(μ-Hphth)(μ₄-phth)(piconol)(Cl)₂]·3H₂O (3) (H₂phth = phthalic acid; H₂isophth = isophthalic acid; piconol = 2-pyridinemethanol; Cl^- = chloride). In methanol-water, the reaction of H₃cpdp with CuCl₂·2H₂O at room temperature leads to the formation of 2. On the other hand, 1 and 3 have been obtained by carrying out the reaction of H₃cpdp with CuCl₂·2H₂O/m-C₆H₄(CO₂Na)₂ and CuCl₂·2H₂O/o-C₆H₄(CO₂Na)₂/piconol, respectively, in methanol-water in the presence of NaOH at ambient temperature. All three complexes have been characterized by elemental analysis, molar electrical conductivity and magnetic moment measurements, FTIR, UV-vis spectroscopy, and PXRD, including single-crystal X-ray structural analyses. The molecular structure of 1 is based on a μ-alkoxide and μ-isophthalate-bridged dimeric [Cu₂] core; the structure of 2 represents a trimeric [Cu₃] core in which a μ-alcohol-bridged dinuclear [Cu₂] unit is exclusively coupled with a [CuCl₂] species by two μ:η¹:η¹-syn-anti carboxylate groups forming a triangular motif; the structure of 3 embodies a tetrameric [Cu₄] core, with two copper(II) ions in a distorted-octahedral coordination environment, one copper(II) ion in a distorted-trigonal-bipyramidal coordination environment, and the other copper(II) ion in a square-planar coordination environment. In fact, 2 and 3 represent rare examples of copper(II)-based multinuclear complexes showing outstanding features of rich coordination chemistry: (i) using a symmetrical dinucleating ligand, trinuclear complex 2 is generated with four- and five-coordination environments around copper(II) ions; (ii) the unsymmetrical tetranuclear complex 3 is obtained by using the same ligand with four-, five- and six-coordination environments around copper(II) ions; (iii) tetracopper(II) complex 3 shows four different bridging modes of carboxylate groups simultaneously such as μ:η², μ:η¹:η¹, μ₃:η²:η¹:η¹, and μ₄:η¹:η¹:η¹:η¹, the μ₄:η¹:η¹:η¹:η¹ mode of phthalate being unprecedented. The formation of these [Cu₂], [Cu₃], and [Cu₄] complexes can be controlled by changing the exogenous ancillary ligands and pH of the reaction solutions, thus allowing an effective tuning of the self-assembly. The magnetic susceptibility measurements suggest that the copper centers in all three complexes are antiferromagnetically coupled. The thermal properties of 1-3 have been investigated by thermogravimetric and differential thermal analytical (TGA and DTA) techniques, indicating that the decomposition of all three complexes proceeds via multistep processes.

Homodinuclear copper(II) and zinc(II) complexes of a carboxylate-rich ligand as synthetic mimics of phosphoester hydrolase in aqueous solutions

The synthesis, characterization and catalytic activities of two homodinuclear Cu(II) and Zn(II) complexes of a carboxylate-rich ligand, N,N'-Bis[2-carboxybenzomethyl]-N,N' -Bis[carboxymethyl]-1,3-diaminopropan-2-ol (H₅ccdp) ligand towards the hydrolysis of (p-nitrophenyl phosphate) (PNPP) and bis(p-nitrophenyl) phosphate (BNPP) substrates in aqueous systems are described. Kinetic investigations were carried out using UV-Vis spectrophotometric techniques at 25 °C and 37 °C and different pH (7-10) conditions. The kinetic studies revealed that the turnover rate (k_cat) values among the PNPP hydrolysis systems, the highest and the lowest k_cat values were displayed by [Cu₂(ccdp)(μ-OAc)]^2- at 2.34 × 10^-6 s^-1 (pH 8 and 37 °C) and 2.13 × 10^-8 s^-1 (pH 8 and 25 °C), respectively. However, similar comparisons among the BNPP hydrolysis revealed that highest and the lowest k_cat values were displayed by [Zn₂(ccdp)(μ-OAc)]^2- at 4.64 × 10^-8 s^-1 (pH 9 and 37 °C) and 2.38 × 10^-9 (pH 9 and 25 °C). Significantly enough, the catalyst-substrate adduct species containing a metal bound PNPP and BNPP have been detected by ESI-MS techniques. Additionally, a PNPP-bound copper complex has been isolated and crystalized using single crystal X-ray diffraction technique. Based on the structural and activity information obtained in this study, reaction mechanisms for the hydrolysis of PNPP have been proposed.

Dinuclear cobalt complexes supported by biphenol and binaphthol-derived bis(salicylaldimine) ligands: synthesis, characterization and catalytic application in β-enaminone synthesis from 1,3-dicarbonyl compounds and aliphatic amines

Biaryl scaffolding ligands form dicobalt clusters, which serve as efficient catalysts in enaminone synthesis under ambient conditions.

Structure and properties of a novel staircase-like decanuclear [CuII10] cluster supported by carbonate and carboxylate bridges

A novel staircase-like decanuclear copper(ii) cluster composed of a pair of [CuII5] pentameric units that are linked together exclusively by two μ₂:η²:η¹carbonate ligands is reported. The cluster also shows a rare μ₃:η²:η¹:η¹bridging coordination mode of benzoate groups of the ligand.

Inorganic Phosphate and Arsenate within New Tetranuclear Copper and Zinc Complexes: Syntheses, Crystal Structures, Magnetic, Electrochemical, and Thermal Studies

Three, PO₄ ^3-/HPO₄ ^2- and AsO₄ ^3--incorporated, new tetranuclear complexes of copper(II) and zinc(II) ions have been synthesized and fully characterized. In methanol-water, reactions of H₃cpdp (H₃cpdp = N,N'-Bis[2-carboxybenzomethyl]-N,N'-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol) with copper(II) chloride in the presence of either NaOH/Na₂HPO₄·2H₂O or KOH/Na₂HAsO₄·7H₂O lead to the isolation of the tetranuclear complexes Na₃[Cu₄(cpdp)₂(μ₄-PO₄)](OH)₂·14H₂O (1) and K₂[Cu₄(cpdp)₂(μ₄-AsO₄)](OH)·16²/₃H₂O (2), respectively. Similarly, the reaction of H₃cpdp with zinc(II) chloride in the presence of NaOH/Na₂HPO₄·2H₂O yields a tetranuclear complex, Na(H₃O)₂[Zn₄(cpdp)₂(μ₄-HPO₄)]Cl₃·12¹/₂H₂O (3). All complexes are characterized by single-crystal X-ray diffraction and other analytical techniques, such as Fourier transform infrared and UV-vis spectroscopy, thermogravimetric and electrochemical studies. The solid-state molecular framework of each complex contains two monocationic [M₂(cpdp)]⁺ (M = Cu, Zn) units, which are exclusively coordinated to either phosphate/hydrogen phosphate or arsenate groups in a unique mode. All three complexes exhibit a μ₄:η¹:η¹:η¹:η¹ bridging mode of the PO₄ ^3-/HPO₄ ^2-/AsO₄ ^3- groups, with each bridging among four metal ions. The thermal properties of all three complexes have been investigated by thermogravimetric analysis. Low-temperature magnetic studies of complexes 1 and 2 disclose moderate antiferromagnetic interactions mediated among the copper centers through alkoxide and phosphate/arsenate bridges. Electrochemical studies of complexes 1 and 2 in dimethylformamide using cyclic voltammetry reveal the presence of a fairly assessable one-electron metal-based irreversible reduction and one quasireversible oxidation couple.

Synthesis and coordination chemistry of 1,1,1-tris-(pyrid-2-yl)ethane

The complexes [ML₂]ⁿ⁺(Mⁿ⁺= Fe²⁺, Co²⁺, Co³⁺, Cu²⁺and Ag⁺), [PdCl₂L] and [CuI(L)] are described. [AgL₂]⁺is an unusual square planar silver(i) centre (left). Exposure of [CuI(L)] to air affords mono- or dinuclear copper(ii)/carbonato products. Two of the copper complexes form crystalline hydrates with complicated hydrogen bond networks (right).

Exploring the catalytic activity of new water soluble dinuclear copper(ii) complexes towards the glycoside hydrolysis

Water soluble dicopper(ii/ii) complexes of a new dinucleating ligand, H₃phpda were synthesized and characterized for the investigation of glycoside hydrolysis.