Jin'an Zhao

Photoluminescent and cytotoxic properties of multinuclear complexes and multinuclear-based polymers with group 12 metals and a tripodal ligand

Four novel multinuclear complexes and multinuclear-based polymers with group 12 metal centers, namely, Zn3(tpbb)Cl6 (1), {[Cd6(tpbb)2Cl12]·2CHCl3·0.5H2O}n (2), Hg4(tpbb)Br8 (3), and Hg4(tpbb)I8 (4), have been synthesized with respect to a new flexible tripodal ligand, 1,3,5-tris((2-(pyridine-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)benzene (tpbb). Complex 1 is a trinuclear cluster, as determined by X-ray crystallography, while 2 features an unprecedented hexanuclear metallacycle-based 2D network with chloride ion bridges. The similar umbrella-like tetranuclear architectures of 3 and 4 with different Hg(II)-halide salts demonstrate that halides with the same tetrahedral coordination geometries of metal centers do not greatly affect the structure of the complexes. Photoluminescent studies indicate that complexes 1 and 2 reveal enhanced and red-shifted solid-state fluorescence at room temperature compared with the ligand, tpbb, while 3 and 4 show prominent phosphorescence behaviors at cryogenic temperatures with lifetimes in the microsecond range. In addition, when tested against a panel of several human carcinoma cell lines (SH-SY5Y, QBC939 and EC109) by standard MTT assay, complex 1 displayed potential cytotoxicity against SH-SY5Y and QBC939 cells and selectivity to different tumor cell lines.

Three Cu(II) complexes based on mixed ligands: their structures and catalytic behaviour

The Cu(II) complexes, [Cu(2,5-pydc)(bmi)(H2O)]n, [Cu2(H2O)2(2,6-pydc)2(btx)]·2H2O and [Cu(btc)2(bmi)2]·1.5H2O, (bmi = 1-[(benzotriazol-yl)methyl)-1H-1,3-imidazole; 2,5-H2pydc = pyridine-2,5-dicarboxylic acid; btx = 1,4-bis(1,2,4-triazol-1-ylmethyl)benzene; H3btc = 1,3,5-benzenetricarboxylate) have been synthesised and their X-ray structures show that hydrogen bonds and π···π stacking interactions are employed in their construction. The complexes can effectively catalyse the oxidative coupling reaction of 2,6-di-tert-butylphenol in good yield and unique selectivity.

Two cyclohexane-type octadecanuclear metalla-macrocycle-based metal organic frameworks and adsorption properties

Two novel porous metal–organic frameworks (MOFs) with {M18(Hbtib)36} (M = Ni(II), Zn(II)) as the basic building unit, namely, [Ni(Hbtib)2]n (1) and [Zn(Hbtib)2·H2O]n (2) [H2btib = 4-((2-butyl-5-(2-carboxy-3-(thiophen-2-yl)prop-1-enyl)-1H-imidazol-1-yl)methyl)] were synthesized using solvothermal reactions. Gas adsorption (N2, H2, CO2 and CH4) studies show that the desolvated solid 1 is a highly effective absorbent for CO2 over CH4 at 273 and 298 K. The results suggest that 1 has potential application in gas separation or purification. In addition, the photoluminescence properties of 2 were also investigated.

Group IIB metal directed complexes with flexible benzimidazole-based connector

Four group IIB metal complexes, namely [ZnCl2(Mbibix)]n (I), [Cd2(Ac)4(Mbibix)2] · (H2O) (II), [HgCl2(DMF)(Mbibix)]2 (III) and [HgI2(Mbibix)]2 (IV), have been achieved via the reaction of corresponding metal salts and organic spacer Mbibix (Mbibix = 1-(3-((2-methyl-1H-benzimidazol-1-yl)methyl)benzyl)-2-methyl-1Hbenzimidazole). Crystal structure analyses reveal that complex I is one-dimensional (1D) zigzag chain, whereas II, III and IV are binuclear motifs (CIF files CCDC nos. 1006224 (I), 1006225 (II), 1006226 (III), 1006227 (IV)). These structures are further stacked into 3D supramolecular architectures via hydrogen bonding and π ⋯ π interactions. The result indicates that the metal centers imparted their influences on the structures and fluorescence behaviors.

In vitro antitumor activity of novel benzimidazole-based Cu(II) complexes

Four benzimidazole-based Cu(II) complexes: Cu2(p-2-bmp)2Br4 (1), Cu2(p-2-bmp)2Cl4 (2), Cu2(p-2-bmb)2(DMF)2Br4·(CHCl3) (3), and Cu(p-2-bmb)(NO3)2·(CHCl3) (4) were isolated and characterized, where p-2-bmp is 1-((2-(pyridine-2-yl)-1H-benzoimidazol-1-yl)methyl)-1H-pyridine and p-2-bmb is 1-((2-(pyridin-2-yl)-1-benzoimidazol-1-yl)methyl)-1H-benzotriazole. Complexes 1 and 2 have binuclear configurations, 3 has a mononuclear structure, and 4has a one-dimensional (1-D) chain skeleton. To evaluate their potential anticancer effects on human carcinoma cells, anti-proliferation, DNA binding and cleavage, and apoptosis elicitation were examined. Compared with complexes 2, 3, and 4, complex 1 exhibited potent in vitro cytotoxicity toward four cell lines (MCF7, EC109, SH-SY5Y and QBC939), with SH-SY5Y cells demonstrating the most sensitivity. Therefore, further in-depth investigations were performed using complex 1. Absorption titration experiments, circular dichroism spectroscopic studies, and ethidium bromide displacement assays suggested that complex 1 binds to DNA through intercalation, significantly cleaves supercoiled pBR322 DNA, and inhibits DNA transcription. Cell cycle analysis revealed that SH-SY5Y cells were arrested in the G2/M phase after treatment with complex 1. Membrane permeability analysis and nuclear staining of SH-SY5Y cells showed that complex 1 could induce apoptosis.

Cytotoxicity, dual-targeting apoptosis induction evaluation of multinuclear cu complexes based on pyrazine-benzimidazole derivative

To investigate the cytotoxicity and mechanism of action of multinuclear Cu complexes against tumor cell lines, two complexes, Cu6(bpbib)4Br8 (1) and Cu2(bpbib)2(BF4)2Cl2 (2) (bpbib = 1,4-bis((2-(pyrazin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)benzene) were synthesized and characterized. Both Cu complexes showed high selectivity toward cancer and not normal cells, and the SMMC7721 cell line showed most sensitivity toward both complexes. Complex 1 exhibited more potent cytotoxicity and enhanced cellular uptake, and therefore, was comprehensively investigated. Complex 1 exhibited dual effects in the inhibition of tumor cell proliferation of SMMC7721 cells, causing nuclear DNA damage and mitochondrial dysfunction involving simultaneous reactive oxygen species (ROS) generation and Ca2+ increase. DNA binding studies suggest that intercalation might be the most probable binding mode. Fluorescence spectrometry also detected a medium affinity of complex 1 to bovine serum albumin (BSA) at distinct temperatures and resulted in BSA fluorescence static quenching.

Mitochondrial and nuclear DNA dual damage induced by 2-(2′-quinolyl)benzimidazole copper complexes with potential anticancer activity

Two copper complexes, [Cu(qbm)Cl2]2 (1) and [Cu(qbm)Br(PPh3)] (2) (where qbm = 2-(2′-quinolyl)benzimidazole), have been prepared and characterized. The interactions of both complexes with calf thymus DNA (CT-DNA) were detected by absorbance and emission spectroscopy methods; the results showed that both complexes were bound to CT-DNA via an intercalative mode. In addition, the two complexes significantly exhibited the free radicals dependence of DNA cleavage activity. MTT assays revealed that complex 2 showed good cell proliferation inhibitory activity against four different human cancer cell lines (SMMC7721, BGC823, HCT116 and HT29), particularly with HCT116 cells. Furthermore, morphological changes and flow cytometry analyses indicated that complex 2 can induce HCT116 cell death by apoptosis. These findings should promote the development of metal-based complexes for use as novel chemotherapeutic agents.

CCDC 1477870: Experimental Crystal Structure Determination

Related Article: Jin-An Zhao, Huai-Bin Yu, Shuang-Cheng Zhi, Rui-Na Mao, Ji-Yong Hu, Xiao-Xiao Wang|2017|Chin.Chem.Lett.|28|1539|doi:10.1016/j.cclet.2017.03.025