Jin’an Zhao

Metal and structure tuned in vitro antitumor activity of benzimidazole-based copper and zinc complexes

Four new complexes, Cu2(p-2-bmb)2Cl4 (1), Cu2(p-2-bmb)2Br4 (2), Zn2(p-3-bmb)2Cl4 (3), and [Cu3(p-3-bmb)2Cl4·(CH3OH)2] n (4), have been synthesized under solvothermal reactions based on V-shaped flexible ligands 1-((2-(pyridin-2-yl)-1H-benzoimidazol-1-yl)methyl)-1Hbenzotriazole (p-2-bmb) and 1-((2-(pyridin-3-yl)-1H-benzoimidazol-1-yl)methyl)-1Hbenzotriazole (p-3-bmb). Complexes 1–3 are binuclear, whereas 4 is an infinite chain with trimetallic units, and then these complexes are further extended into 3D supramolecular architectures by π…π interactions and hydrogen bonds. In vitro antitumor activities of these complexes on four human tumor cell lines (gastric tumor cell line, esophagus tumor cell line, liver tumor cell line, colon tumor cell line) were evaluated by MTT assay. The results exhibit that these complexes inhibit the growth of cancer cells by inducing apoptosis, and the inhibition effect shows time- and dose-effect relationship.

Metallacycle-based complexes based on a flexible pyridyl–benzimidazole derivative

Three new coordination complexes, {Cd(pbmb)(NO3)2} n (1), {Ag(pbmb)(NO3)(C3H6O)} n (2), and {Hg2(pbmb)2Cl4} n (3), have been synthesized under solvothermal or solution reactions based on a flexible N-heterocyclic ligand 1-((2-(pyridin-4-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (pbmb) and structurally characterized by single-crystal X-ray diffraction, IR spectrum, and elemental analyses. Both 1 and 2 display a 1-D chain structure with metallacycle unit while 3 shows a binuclear cycle motif. The aromatic rings are directing groups for π ··· π stacking interactions. The π ··· π interactions and hydrogen bonds extend the simple chain structure and binuclear structure to 3-D supramolecular architectures. Complexes 1 and 3 exhibit strong luminescence in the solid state at room temperature whereas 2 shows fluorescence quenching.

Cytotoxicity towards human alimentary system carcinoma cells resulting from diverse copper(II) complexes

To investigate the potential cytotoxicity of copper(II)-based complexes, three coordination compounds with heterocyclic ligands, Cu(pbmbt)Cl2(CH3OH) (1), Cu2(ddbib)2(NO3)4·3CH3OH (2), and Cu3(ttmtmb)2Cl6·2.5H2O (3), which include mononuclear, dinuclear, and trinuclear structures, have been synthesized from reactions of corresponding copper(II) salts with 1-((2-pyrazinyl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (pbmbt), 2-(2,3-dihydropyrazin-2-yl)-1-((4-((2-(2,3-dihydropyrazin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)phenyl)methyl)-1H-benzo[d]imidazole (ddbib), and 1,1′,1′′-((2,4,6-trimethylbenzene-1,3,5-triyl)tris(methylene)tris(2-methyl-1H-benzoimidazole) (ttmtmb), respectively. IC50 values revealed that 2 and 3 show strong cytotoxicity, whereas 1 is weakly cytotoxic after being tested against a panel of several human alimentary system carcinoma cell lines (SGC7901, EC109, SMMC7721, and HT29). The number of copper centers and different structures could make a tremendous difference on their cytotoxicity. Graphical Abstract Three coordination compounds with heterocyclic ligands were constructed to investigate the potential cytotoxicity of copper(II)-based complexes. IC50 values revealed that complexes 2 and 3 show strong cytotoxicity, whereas complex 1 is weakly cytotoxic after being tested by MTT assay against a panel of several human alimentary system carcinoma cell lines.

Synthesis, crystal structure, DNA/BSA interaction and in vitro antitumor activity of N-heterocycle Cu(II) and Co(II) complexes

Abstract Investigation of N-heterocycle transition metal complexes has led to the discovery of metal-based antitumor agents. Herein, two binuclear complexes, [Cu(p-4-bmb)(Ac)2]2 (1) and [Co(p-4-bmp)Cl2]2 (2), were prepared and characterized. The interactions of 1 and 2 with calf thymus (CT)-DNA and bovine serum albumin (BSA) were detected by absorbance and emission spectroscopy. The complexes bind to CT-DNA via an intercalative mode and show moderate affinity to BSA. Both complexes exhibited remarkable DNA cleavage activity. The MTT assay demonstrated that 1 exhibited higher cytotoxicity against three human alimentary system carcinoma cell lines compared to 2. Further, a cellular uptake assay demonstrated that 1 can accumulate in the nucleus and mitochondria of SMMC7721 cells to induce DNA damage and mitochondrial dysfunction. Fluorescence staining and flow cytometry analyses revealed that 1 can induce cell death by apoptosis. These findings should promote the development of benzimidazole-based transition metal complexes as novel chemotherapy agents with fewer side effects than conventional antitumor drugs.

Construction of three 2-D silver(I) coordination architectures with a flexible pyrazine-based ligand

To investigate the impact of weak intermolecular interactions in construction of metal–organic frameworks, three silver(I) coordination complexes with the flexible N-heterocyclic ligand 1-((2-pyrazinyl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole (PBMBT), {Ag(C18H13N7)NO3} n (1), {Ag(C18H13N7)ClO4} n (2), and {Ag(C18H13N7)SO3CF3} n (3), were prepared under solvothermal conditions and structurally characterized by single-crystal X-ray diffraction, IR spectrum, and elemental analyses. Complexes 1–3 exhibit 2-D reticulate structures, and these 2-D layers are further connected into 3-D supramolecular motifs by π···π interactions and hydrogen bonds. Luminescence indicates that 1–3 show analogous fluorescent emissions compared with the PBMBT in the solid state at room temperature.

A holodirected Pb(II) architecture based on bifunctional tetrazole-carboxylate and photoluminescence

A new 1-D Pb(II) complex {[Pb2(H2O)4(tppbc)2] · (CH3)2NCHO} n (1) based on tetrazole-carboxylate bifunctional ligand has been prepared and characterized (tppbc = 3-(4-(2-(1H-tetrazol-5-yl)phenyl-4-yl)phenyl)-2-ethoxy-3H-benzimidazole-4-carboxylic acid). Photo-luminescence measurements indicate that although the fluorescence of tppbc is quenched after coordination, the Pb(II) complex shows strong intense phosphorescence emission. Lifetimes at 298 K and low temperatures agree with the large Stokes shift of 1.

Anion-driven Ag(I) coordination architectures: structural diversity and photoluminescence behaviors

Abstract To observe anion impact on structural diversity of coordination architectures, three 1-D Ag(I) complexes with distinct features have been prepared, {[Ag(bpbib)2(NO3)]·C3NH9O)}n (1), [Ag2(bpbib)2·(BF4)2]n (2), and [Ag2(bpbib)2·(ClO4)2]n (3), by the reactions of 4,4′-bis((2-(pyridin-2-yl)-1H-benzo[d]imidazol-1-yl)methyl)biphenyl (bpbib) with Ag(I) salts. Complex 1 is a 1-D helical chain, whereas 2 and 3 bear ligand-unsupported Ag(I)···Ag(I) interaction-directed 1-D structural motif, with synergetic working of flexible organic linker and anions. All complexes exhibit strong triplet state emission at cryogenic temperatures, which profits from the reduction of nonradiative transitions.

Ag/Cd coordination architecture and photoluminescence behaviors

Abstract Three coordination architectures, {[Ag4(pbmb)4·(BF4)4](CH3OH)2·H2O}n (1), {[Cd2(pbmb)4](ClO4)4·(CH3OH)5}n (2), and [Cd4(pbmb)4·I8(CH3OH)2]n (3) (pbmb = 1-((2-(pyridin-2-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole), are built up from Ag(I)/Cd(II) salts and a flexible pyridyl-benzimidazole-based organic spacer. Single-crystal analysis shows that 1 and 2 have 1-D chains, while 3 displays a tetranuclear structure. All complexes exhibit different coordination geometries and properties, which can be attributed to the difference between the metal centers or anions. In the case of 1 in particular, the Ag⋯Ag interactions play a crucial role in the formation of a supramolecular architecture. The binuclear-based complex consists of a pair of Ag⋯Ag contacts (ca. 2.953 Å), and it exhibits intense triplet emission with large Stokes shift and high thermal stability. Compared to pbmb, 2 has excellent high-energy fluorescence properties, while 1 and 3 exhibit mainly low-energy emission. Therefore, it can be concluded that the heavy atom effect has a causative influence in enhancing the triplet state radiative rate, resulting in large Stokes’ shift of the complex.

Two Ag(I) Complexes Constructed From the Flexible Tripodal Pyridyl-Benzimidazole-Based Connector

Two new complexes {Ag2(TPBT)(NO3)2}n (1) and Ag2(TPBT)4 (ClO4)2 (2) were constructed by the reaction of tripodal connector 1,3,5-[(2-pyridyl)-1H-benzoimidazol- 1-methyl)-2,4,6-trimethylbenzene (TPBT) and corresponding silver salts under solvothermal conditions. The synergistic effect of the flexible tripodal ligand and anions has led to different complexes 1 and 2. Complex 1 is a 2D layer with the binuclear units with the Ag···Ag distance of 2.9054 Å, whereas 2 is a binuclear motif with Ag···Ag separation of 10.526 Å. Both 1 and 2 are further extended into 3D supramolecular architectures by hydrogen bonds and π···π interactions, which exhibit weak luminescence emission in the solid state at room temperature. Supplementary material is available for this article. Go to the publishers online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

Structurally diverse complexes from a bifunctional benzimidazole-carboxylate ligand

Three new complexes, namely {Ag2(Hmbbc)2(SO3CF3)2}n (1), Ag2(Hmbbc)2(NO3)2(DMF)2(CH3OH) (2), and Hg2(Hmbbc)2(I)4(DMF)2 (3) were constructed by the reaction of 4′-[4-methyl-6-(1-methyl-1H-benzimidazolyl-l-2-group)-2-n-propyl-1H-benzimidazolyl methyl]-biphenyl-2-carboxylic acid (Hmbbc) with Ag(I) or Hg(II) salts under solvothermal or solution reactions. In the complexes, the Hmbbc ligand exhibits different coordination modes, giving various crystal architectures. X-ray analysis demonstrates that 1 has a 2D layer structure, while 2 and 3 are binuclear. All three complexes are further extended into 3D supramolecular architectures through hydrogen bonds and π···π interactions. They exhibit luminescence emission in the solid state at room temperature.