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Isomers sometimes play a fundamental role in the formation of coordination architectures. In this article, bifunctional 5-(n-pyridyl)tetrazole-2-isopropanoic acid (n = 2, 3) has been designed and prepared. Then, reactions of Ca(NO3)2·4H2O with isomeric 5-(n-pyridyl)tetrazole-2-isopropanoic acid (denoted as Hn-pytzipa, n = 2, 3) afforded mononuclear [Ca(2-pytzipa)2(H2O)4] (1) and one-dimensional [Ca(3-pytzipa)2(H2O)2]n (2), respectively. In 1, 2-pytzipa is a bidentate ligand which chelates one Ca(II) via the nitrogen atoms of the pyridine and tetrazole rings while in 2, 3-pytzipa bridges adjacent Ca(II) centers in a μ 1,1,3-COO mode. PEG-5000 (poly(ethyleneglycol-5000)) coated [Ca(2-pytzipa)2(H2O)4] (1) and [Ca(3-pytzipa)2(H2O)2]n (2) nanoparticles (NPs) show toxicity towards Hela cells, but the ligands are non-toxic in nature and 2 is superior to 1. Furthermore, cell migration across a 2D artificial gap indicates that both NPs can inhibit the migration of Hela cells.

3,3-di(1H-tetrazol-5-yl)pentanedioic acid (H4dtzpda) can display tunable valence when reacted with different metal ions because it has four acidic hydrogen atoms of both tetrazole rings and carboxylate groups. Solvothermal reactions of H4dtzpda with La(NO3)2·6H2O or La(NO3)3·6H2O/Cu(NO3)2·6H2O afforded a one dimensional [La(Hdtzpda)(H2O)4]·4H2O (1) and a three dimensional [La2Cu(dtzpda)2(H2O)10]·4H2O (2), respectively, where only three acidic hydrogen atoms of H4dtzpda are deprotonated in compound 1 while all the four acidic ones are deprotonated in compound 2. In compound 1, Hdtzpda3- is a penta-dentate ligand to bridge La(III) centers via only oxygen atoms of the carboxylate group while in compound 2, dtzpda4- is a hepta-dentate one via not only the oxygen atoms of the carboxylate group but also the nitrogen atoms of the tetrazole rings. PEG-5000 (poly(ethyleneglycol-5000)) coated compound 1 or 2 nanoparticles (NPs) have good dispersity in water. Cytotoxicity study on A549 cells (human caucasian lung carcinoma) shows that compound 2 (half-maximal inhibitory concentration, IC50～18 μg/mL) is superior to compound 1 (IC50～38 μg/mL). Furthermore, both NPs of the two compounds are able to inhibit the migration of A549 cells, indicating their potential to inhibit the transfer of tumors in vivo.

Ru(II) compounds are potential candidates for photodynamic therapy (PDT). In the present study, a Ru(II) compound based on 3-(2-pyridyl)pyrazole (Hpypz) and 2,2′-bipyridine has been prepared and characterized. This compound can self-assemble to form nanoparticles (NPs) by nanoprecipitation in distilled water. These NPs with a mean size of 92 nm have good passive targeting by enhanced permeability and retention effect (EPR). In vitro studies on HeLa cells show that these NPs have high phototoxicity and a low IC50 (half-maximal inhibitory concentration) of only 8 μg mL−1 (12 μM), but they also have negligible dark toxicity. Moreover, such NPs can inhibit the migration of HeLa cells, indicating their potential to interfere with the transfer of tumors in vivo. Furthermore, in vivo investigations on nude mice demonstrate that such NPs can effectively inhibit the growth of the tumor. After treatment for 10 cycles, an obvious decrease in the tumor volume can be observed and in addition, the main organs (heart, liver, spleen, lung and kidney) suffer no damage, which indicates the high phototoxicity, low toxicity and excellent biocompatibility of these NPs.

An energetic material [Zn2(btzphda)2(H2O)4(dpp)2]·2DMF·4H2O with high decomposition enthalpy of − 748.35 J/g was prepared by the reaction of H2btzphda, dpp and Zn(NO3)2·6H2O under solvothermal conditions, where btzphda = 1,4-bis(tetrazol-5-yl)benzene-N2,N2′-diacetato, dpp = 1.3-di(4-pyridyl)propane and DMF = N,N′-dimethylformamide. The luminescence properties of H2btzphda and [Zn2(btzphda)2(H2O)4(dpp)2]·2DMF·4H2O were investigated at room temperature in the solid state (Hitachi F4600 spectrofluorometer). Furthermore, the thermal decomposition behavior of the compound is characterized by differential scanning calorimetry (DSC) and thermogravimetric-differential thermogravimetric (TG-DTG) analyses. The entropy of activation (ΔH), enthalpy of activation (ΔS) and the free energy of activation (ΔG) for the decomposition temperature were ΔH = 250.64 kJ/mol, ΔS = 222.75 J·mol− 1·K− 1 and ΔG = 134.10 kJ/mol.

A mononuclear [Cu(2-pytzipa)2(H2O)2]·2H2O (2-pytzipa = 5-(2-pyridyl)tetrazole-2-isopropanoic anion) has been prepared and characterized by elemental analysis, IR and single crystal X-ray diffraction. PEG-5000 (poly(ethyleneglycol-5000)) coated [Cu(2-pytzipa)2(H2O)2]·2H2O nanoparticles can disperse into distilled water. In vitro study on Hela cells shows that H2-pytzipa is nontoxic while [Cu(2-pytzipa)2(H2O)2]·2H2O NPs show high toxicity. In addition, such NPs can inhibit the migration of Hela cells effectively, indicating their potential to interfere with the transfer of tumors in vivo.

Reactions of 1H-tetrazolate-5-acetic acid(H2tza) with Nd(NO3)3·6H2O or Dy(NO3)3·6H2O with the presence of KOH under solvothermal conditions, produced two new coordination compounds, [M2(tza)3(H2O)6]·2H2O [M=Nd(1), Dy(2)]. Both compounds were structurally characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction. Compounds 1 and 2 reveal 1D structures via bridging tza as linker. Furthermore, the compounds 1 and 2 showed a specific and good catalytic behavior for the polymerization of styrene, and the polymerization showed controlled characteristics.

A novel 1D coordination compound [Pr2(tza)3(H2O)6]n·4nH2O (1) (tza = tetrazole-5-acetato) was synthesized by the reaction of tetrazole-5-acetic acid with Pr(NO3)3·6H2O in the presence of KOH. This complex showed a specific and good catalytic behavior in the polymerization of styrene. The high molecular weight polymers with narrow molecular weight distributions in good yields were obtained within a few minutes.