A tetranuclear nickel(II) complex, [Ni4(L)4](ClO4)4·C2H3N·2H2O, with an asymmetric Ni4O4 open-cubane-like core

A tetra­nuclear complex with an open-cubane like structure was synthesized from 2-meth­oxy-6-(pyridin-2-yl-hydrazonometh­yl)-phenol and characterized using micro-analytical and spectroscopic techniques, and single-crystal X-ray diffraction analysis.

A tetra­nuclear complex with an open-cubane-like core structure was synthesized from 2-meth­oxy-6-(pyridin-2-yl-hydrazonometh­yl)phenol (HL), namely, cyclo-tetra­kis­(μ-2-meth­oxy-6-{[2-(pyridin-2-yl)hydrazin-1-yl­idene]meth­yl}pheno­lato)tetra­nickel(II) tetra­kis­(perchlorate) aceto­nitrile monosolvate dihydrate, [Ni₄(C₁₃H₁₂N₃O₂)₄](ClO₄)₄·C₂H₃N·2H₂O, and characterized using micro-analytical and spectroscopic techniques. The crystal-structure determination reveals the formation of a distorted Ni₄O₄ cubane-like core architecture encapsulated by four hydrazone Schiff base (HL) mol­ecules. A open-cube tetra­nuclear architecture is created in which nickel(II) ions of the NiN₂O₃ unit are connected by μ₂-O anions of the phenolate moiety of HL. In this complex, each Ni centre has a slightly distorted square-pyramidal coordination environment. The supra­molecular architectures are stabilized via the presence of various inter­molecular hydrogen bonds and (ar­yl–aryl, ar­yl–chelate and chelate–chelate) stacking inter­actions.

Novel {Cu4} and {Cu4Cd6} clusters derived from flexible aminoalcohols: synthesis, characterization, crystal structures, and evaluation of anticancer properties

Two new copper clusters, {Cu₄} and {Cu₄Cd₆}, with polydentate aminoalcohol ligands, diethanol propanolamine (H₃L¹) and bis-tris{2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)propane-1,3-diol} (H₆L²), have been synthesized under mild conditions and characterized thoroughly by single-crystal X-ray diffraction (XRD), infrared spectroscopy, elemental analysis, powder XRD, magnetic and DFT studies, and absorption and fluorescence spectroscopy. The cluster {Cu₄} exhibits a rare tetranuclear copper cubane core whereas {Cu₄Cd₆} forms an unusual heterometallic cage owing to the introduction of the second metal Cd into the ligand. A hexapodal ligand (H₆L²) with N and O donor atoms was chosen deliberately for the construction of a high-nuclearity cluster, i.e., {Cu₄Cd₆}. Interestingly, both the clusters displayed significant cytotoxicity towards human cervical (HeLa) and lung (A549) cancer cells as evident from the shallow IC₅₀ values [15.6 ± 0.8 μM (HeLa), 18.5 ± 1.9 μM (A549) for {Cu₄}, and 11.1 ± 1.5 μM (HeLa), 10.2 ± 1.3 μM (A549) for {Cu₄Cd₆}] obtained after a 24 h incubation. However, moderate toxicity was observed toward immortalized lung epithelial normal cells (HPL1D) with IC₅₀ values of 32.4 ± 1.2 μM for {Cu₄} and 27.6 ± 1.7 μM for {Cu₄Cd₆}. A cellular apoptotic study using HeLa cells revealed that the {Cu₄} cluster triggered apoptosis at both the early and late phases while the {Cu₄Cd₆} cluster facilitate apoptosis mainly at the late apoptotic stage. A standard 2',7'-dichlorodihydrofluorescein-diacetate (DCFH-DA) test affirms that both the clusters enhanced ROS production inside the cancer cells, responsible for promoting cell apoptosis. The decanuclear {Cu₄Cd₆} clusters demonstrated better anticancer activity compared to the tetranuclear {Cu₄} clusters, indicating the role of high nuclearity and additional Cd metal in the enhanced intracellular production of ROS.

Hexanuclear copper(II) complex of 2-hy-droxy-N,N'-bis-[1-(2-hy-droxy-phen-yl)ethyl-idene]propane-1,3-di-amine incorporating an open-cubane core

The title mol-ecular structure, namely, di-aqua-tris-(μ3-1,3-bis-{[1-(2-oxidophen-yl)ethyl-idene]amino}-propan-2-olato)-μ3-hydroxido-dinitrato-hexa-copper(II) ethanol tris-olvate, [Cu6(C19H19N2O3)3(NO3)2(OH)(H2O)2]·3C2H5OH, corres-ponds to a non-symmetric hexa-nuclear copper complex. The complex exhibits one core in which three CuII metal centres are mutually inter-connected, two by two, via three phenolato oxygen anions acting in a μ2-mode. These three copper cations are inter-connected in a μ3-mode by one hydroxyl group. An open-cube structure is generated in which each of the CuII cations of the three CuO4N units is connected by two μ2-O anions from phenolate groups and one μ3-O atom from a hy-droxy anion. Each of the three penta-coordinated CuII cations situated in the open-cube unit has a distorted NO4 square-pyramidal environment. Each of these three CuII centres is inter-connected with another CuII cation via one enolate O atom in μ2-mode, yielding one CuNO4 unit and two CuNO3 units. The penta-coordinated CuII atom has a distorted square-pyramidal environment while the two tetra-coordinated copper(II) cations are situated in a square-planar environment. A series of intra-molecular O-H⋯O hydrogen bonds are observed. In the crystal, the units are connected two by two by inter-molecular C-H⋯O and O-H⋯O hydrogen bonds, thus forming sheets parallel to the ac plane.

Tetranuclear copper(ii) cubane complexes derived from self-assembled 1,3-dimethyl-5-(o-phenolate-azo)-6-aminouracil: structures, non-covalent interactions and magnetic property

A new doubly opened 4 + 2 Cu₄O₄ cubane cluster exhibits strong antiferromagnetic exchange coupling with J₁ = −110.1 cm⁻¹, and J₂ = −27.1 cm⁻¹.

Chiral tetranuclear copper(ii) complexes: synthesis, optical and magnetic properties

The chiral tetranuclear Cu(ii) cubane complexes with the general molecular formula [Cu₄(R-L₁)₄] (R-1) and [Cu₄(S-L₁)₄] (S-1) exhibit ferromagnetic exchange coupling, which is in contrast to the literature reports. This is corroborated by theoretical calculations.

Crystal structure and photoluminescence properties of a new monomeric copper(II) complex: bis(3-{[(3-hydroxypropyl)imino]methyl}-4-nitrophenolato-κ3O,N,O')copper(II)

Copper(II)-Schiff base complexes have attracted extensive interest due to their structural, electronic, magnetic and luminescence properties. The title novel monomeric Cu^II complex, [Cu(C₁₀H₁₁N₂O₄)₂], has been synthesized by the reaction of 3-{[(3-hydroxypropyl)imino]methyl}-4-nitrophenol (H₂L) and copper(II) acetate monohydrate in methanol, and was characterized by elemental analysis, UV and IR spectroscopies, single-crystal X-ray diffraction analysis and a photoluminescence study. The Cu^II atom is located on a centre of inversion and is coordinated by two imine N atoms, two phenoxy O atoms in a mutual trans disposition and two hydroxy O atoms in axial positions, forming an elongated octahedral geometry. In the crystal, intermolecular O-H...O hydrogen bonds link the molecules to form a one-dimensional chain structure and π-π contacts also connect the molecules to form a three-dimensional structure. The solid-state photoluminescence properties of the complex and free H₂L have been investigated at room temperature in the visible region. When the complex and H₂L are excited under UV light at 349 nm, the complex displays a strong green emission at 520 nm and H₂L displays a blue emission at 480 nm.

A new stepped tetranuclear copper(II) complex: synthesis, crystal structure and photoluminescence properties

Binuclear and tetranuclear copper(II) complexes are of interest because of their structural, magnetic and photoluminescence properties. Of the several important configurations of tetranuclear copper(II) complexes, there are limited reports on the crystal structures and solid-state photoluminescence properties of `stepped' tetranuclear copper(II) complexes. A new Cu^II complex, namely bis{μ₃-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}bis{μ₂-3-[(4-methoxy-2-oxidobenzylidene)amino]propanolato}tetracopper(II), [Cu₄(C₁₁H₁₃NO₃)₄], has been synthesized and characterized using elemental analysis, FT-IR, solid-state UV-Vis spectroscopy and single-crystal X-ray diffraction. The crystal structure determination shows that the complex is a stepped tetranuclear structure consisting of two dinuclear [Cu₂(L)₂] units {L is 3-[(4-methoxy-2-oxidobenzylidene)amino]propanolate}. The two terminal Cu^II atoms are four-coordinated in square-planar environments, while the two central Cu^II atoms are five-coordinated in square-pyramidal environments. The solid-state photoluminescence properties of both the complex and 3-[(2-hydroxy-4-methoxybenzylidene)amino]propanol (H₂L) have been investigated at room temperature in the visible region. When the complex and H₂L are excited under UV light at 349 nm, the complex displays a strong blue emission at 469 nm and H₂L displays a green emission at 515 nm.