Syntheses, crystal structure, thermal behavior, and anti-tumor activity of three ternary metal complexes with 2-chloro-5-nitrobenzoic acid and heterocyclic compounds

Three complexes, namely complex (1), complex (2), and complex (3), were synthesized and characterized by X-ray diffraction, thermogravimetric study, and elemental study. Complex (1) comprises discrete binuclear clusters, where two oxygen atoms of 2-chloro-5-nitrobenzoic acid bridge the two copper atoms. Complex (2) is a six-coordination structure consisting of four nitrogen atoms and two oxygen atoms in 2-chloro-5-nitrobenzoic acid and 1,10-phenanthroline to furnish a twisted octahedron. Complex (3) is a six-coordination structure consisting of four oxygen atoms and two nitrogen atoms from the 2-chloro-5-nitrobenzoic acid, methanol, and 2,2′-dipyridyl to furnish a distorted octahedral geometry. Metal complexes’ anti-tumor activity was also investigated by the MTT assay. Of the complexes tested, complex (1) could induce apoptosis in these A549 lung cancer and Caco-2 colon adenocarcinoma cells and complex (2) could induce apoptosis in Caco-2 colon adenocarcinoma cells. CCDC for complex (1) was 1543354, CCDC for complex (2) was 1546991, and CCDC for complex (3) was 1543417.

A Family of [Zn6] Complexes from the Carboxylate-Bridge-Supported Assembly of [Zn2] Building Units: Synthetic, Structural, Spectroscopic, and Systematic Biological Studies

The three discrete [Zn₆] complexes [Na₃Zn₆(cpdp)₃(μ-Bz)₃(CH₃OH)₆][ZnCl₄][ZnCl₃(H₂O)]·3CH₃OH·1.5H₂O (1), [Na₃Zn₆(cpdp)₃(μ-p-OBz)₃(CH₃OH)₆]·2H₂O (2), and [Na₃Zn₆(cpdp)₃(μ-p-NO₂Bz)₃(CH₃OH)₆]Cl₃·2H₂O (3), supported by the carboxylate-based multidentate ligand N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H₃cpdp), have been successfully synthesized and fully characterized (Bz = benzoate; p-OBz = dianion of p-hydroxybenzoic acid; p-NO₂Bz = p-nitrobenzoate). The complexes have been characterized by elemental analysis, FTIR, UV-vis, NMR spectroscopy, PXRD, and thermal analysis, including single-crystal X-ray crystallography of 1 and 2. The molecular architectures of 1-3 are built from the self-assembly of their corresponding [Zn₂] units, which are interconnected to the central [Na₃(CH₃OH)₆]³⁺ core by six endogenous benzoate groups, with each linking one Zn(II) and one Na(I) ion in a μ₂:η¹:η¹-syn-anti bidentate fashion. The composition of the (cpdp^3-)₃/(Zn²⁺)₆ complexes in 1-3 has been observed to be 1:2, on the basis of the UV-vis titration and NMR spectroscopic results, which is further supported by X-ray crystallography. Systematic biological studies performed with a mice model suggested possible antidiabetic efficacy as well as anticancer activities of the complexes. When complexes 1-3 were administered intraperitoneally in mice, 1 showed a lowering in the blood glucose level, overall maintenance of the pancreatic tissue mass, restriction of DNA damage in pancreatic cells, and retention of lipid droplet (LD) frequency, whereas 2 and 3 showed hepatic tissue mass consistency by inhibiting the DNA damage in hepatic cells, prior to the exposure to a potent diabetic inducer, alloxan (ALX). Similar trends of results were observed in inhibiting the generation of reactive oxygen species (ROS) in the pancreatic and hepatic cells, as examined by spectrofluorometric methods. Thus, 1 seems to be a better compound for overall diabetic management and control, whereas 2 and 3 seem to be promising compounds for designing chemopreventive drugs against hepatic carcinoma.

Novel copper complexes of metronidazole and metronidazole benzoate: synthesis, characterization, biological and computational studies

Synthesis and characterization of novel copper complexes of metronidazole benzoate (MTZ Benz), metronidazole (MTZ) in the presence of another ligand; dichloroacetic acid (DCA) were compared and reported in the present work. Different bacterial and fungus strains were ascertained to evaluate the biological potency of the synthesized complexes, that is, Escherichia coli, Bordetella bronceptica, Staphylococcus epidermidis, Baccilus pumilus, Staphylococcus aureus and yeast strain Saccharomyces cerevisiae. Agar diffusion method was employed to investigate in vitro antibacterial activities of the synthesized metal complexes and the tested parent ligands. α-Amylase and α-glucosidase inhibition studies of the synthesized complexes were also carried out. The antibacterial potential and α-amylase and α-glucosidase inhibition studies of complexes were further investigated by molecular docking studies, which supported the experimental results. Significant α-amylase and α-glucosidase inhibition activities were shown by the synthesized complexes. S-1 and S-5 were found to be most inhibitors of α-amylase and α-glucosidase having IC₅₀ 42.50, 44.80 and 4.52 µg/mL, 4.80 µg/mL, respectively. The newly synthesized copper complexes showed overall better biological activities compared to each parent ligands used.Communicated by Ramaswamy H. Sarma.

Solvent-driven structural topology involving energetically significant intra- and intermolecular chelate ring contacts and anticancer activities of Cu(ii) phenanthroline complexes involving benzoates: experimental and theoretical studies

Two new coordination solids [Cu₂(μ²-Bz)₄(CH₃OH)₂][Cu₂(η²-Bz)₂(phen)₂(H₂O)₂]·(NO₃)₂ (1) and [Cu(phen)(H₂O)(Bz)(η²-Bz)] (2) (phen = 1,10-phenanthroline; Bz = benzoate) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (IR, UV-vis-NIR and ESR) and single crystal X-ray diffraction techniques. Change of the solvent from methanol to DMF results in changes in the architectures that are triggered by a change from square pyramidal to octahedral coordination at the divalent metal centers for complexes 1 and 2 respectively. The structural topology of the complexes is established by the interplay of strong O-H⋯O and weak C-H⋯O, C-H⋯C, π-π stacking interactions. Unconventional parallel intramolecular and anti-parallel intermolecular contacts involving the chelate rings (CR) also stabilize the structures. The energetic analyses of the structures evidence that the parallel arrangement is energetically favoured which is likely due to the presence of the Cu⋯Cu cuprophilic interaction in 1 that is not established in 2. Compound 1 exhibits the highest antibacterial activity against Rhizobium leguminosarum among the tested cultures. In vitro cytotoxicity and apoptosis studies were carried out for compounds 1 and 2 on malignant Dalton's lymphoma cell line (DL). Both compounds showed a significant effect on the decrease in cell viability as compared to a control, while compound 2 induced remarkable cytotoxicity towards DL cells. Treatment also showed the appearance of membrane blebbing, chromatin condensation and fragmented nuclei which are typical characteristic features of apoptotic cell death. Furthermore, a docking study revealed that both compounds docked in the active sites of all the cancer target proteins under study. Moreover, SAR analysis revealed that oxygen and nitrogen atoms of compound 1 and the oxygen atoms of compound 2 are crucial for biological activities.

Copper(II) Complexes with Bulky N-Substituted Diethanolamines: High-Field Electron Paramagnetic Resonance, Magnetic, and Catalytic Studies in Oxidative Cyclohexane Amidation

The novel coordination compounds [Cu₂(H ^tBuDea)₂(OAc)₂] (1) and [Cu₂(H ⁿBuDea)₂Cl₂]· nH₂O (2) have been prepared through the reaction of the respective copper(II) salts with N- tert-butyldiethanolamine (H₂ ^tBuDea, for 1) or N-butyldiethanolamine (H₂ ⁿBuDea, for 2) in methanol solution. Crystallographic analysis reveals that, in spite of the common binuclear {Cu₂(μ-O)₂} core, the supramolecular structures of the complexes are drastically different. In 1 binuclear molecules are linked together by H-bonds into 1D chains, while in 2 the neighboring pairs of binuclear molecules are H-bonded, forming tetranuclear aggregates. Variable-temperature (1.8-300 K) magnetic susceptibility measurements of 1 and 2 show a dominant antiferromagnetic behavior. Both complexes are also studied by HF-EPR spectroscopy. While the interaction between Cu(II) centers in 1 can be described by a single coupling constant J = 130.1(3) cm^-1 (using H = JS₁ S₂), the crystallographically different {Cu₂(μ-O)₂} pairs in 2 are expected exchange from ferro- to antiferromagnetic behavior (with J ranging from -32 to 110 cm^-1, according to DFT calculations). Complexes 1 and 2 act as catalysts in the amidation of cyclohexane with benzamide, employing ^tBuOO ^tBu as oxidant. The maximum achieved conversion of benzamide (20%, after 24 h reaction time) was observed in the 1/ ^tBuOO ^tBu system. In the cases of ^tBuOO(O)CPh or ^tBuOOH oxidants, no significant amidation product was observed, while for ^tBuOO(O)CPh, the oxidative dehydrogenation of cyclohexane occurred, giving cyclohexene, to afford the allylic ester (cyclohex-2-en-1-yl benzoate) as the main reaction product.

Oleuropein shows copper complexing properties and noxious effect on cultured SH-SY5Y neuroblastoma cells depending on cell copper content

The secoiridoid oleuropein is a non-flavonoid polyphenol, found in the fruit, leaves and food derivatives from Olea europea. Like other polyphenols it shows a very low toxicity towards healthy tissues and a protective action against cancer or neurodegeneration, but its mechanism of action is not yet understood. In the present report we have used optical and ESR spectroscopy as well as molecular modelling to demonstrate that oleuropein forms a complex with the transition metal copper; the dysmetabolism of this metal is suspected to be involved in both cancer and neurodegeneration. Experiments carried out with the aglycon derivative of oleuropein, produced by β-glycosidase treatment of oleuropein glycoside, showed that also the aglycon forms copper-complexes, but with different spectroscopic features than the glycosidic form. Molecular modelling analysis confirmed that two oleuropein molecules (glycosidic or aglycon forms) can easily coordinate one copper ion. The relationship between oleuropein and copper was investigated in SH-SY5Y human neuroblastoma cells. When cells were depleted of copper by treatment with the copper chelator triethylenetetramine (Trien), that binds copper with higher affinity than oleuropein, oleuropein was less toxic than to copper-adequate cells. Conversely, incubation of SH-SY5Y cells with exogenous copper sulphate increased cell susceptibility to oleuropein. Furthermore SH-SY5Y cells differentiated by retinoic acid pre-treatment showed a lower level of copper, and were more resistant to oleuropein treatment. The oleuropein aglycon was not toxic towards SH-SY5Y cells. In conclusion, the copper-oleuropein complex may be involved in the toxicity of oleuropein towards tumour cells, depending on their copper level.

Centric and acentric networks using low-symmetry heterotopic carboxylate/pyridyl ligands

Four isomeric pyridyl/carboxylate ligands demonstrate the appliability of low-symmetry ligands to the formation of chiral materials.