Direct Synthesis and Characterization of New Copper(II) and Zinc(II) 5-R-Tetrazolato Complexes [R= Me, Ph, 4-Py] with Ethylenediamine and DMSO as Coligands

Supramolecular Frameworks and a Luminescent Coordination Polymer from New β-Diketone/Tetrazole Ligands

Mixed multidentate linkers with donor groups of different types can be fruitfully exploited in the self-assembly of coordination polymers (CPs) and Metal-Organic Frameworks (MOFs). In this work we develop new ligands containing a β-diketone chelating functionality, to better control the stereochemistry at the metal center, and tetrazolyl multidentate bridging groups, a combination not yet explored for networking with metal ions. The new ligands, 1,3-bis(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H3L1) and 1-phenyl-3-(4-(1H-tetrazol-5-yl)phenyl)-1,3-propanedione (H2L2), are synthesized from the corresponding nitrile precursors by [2+3] dipolar cycloaddition of azide under metal-free catalytic conditions. Crystal structure analysis evidences the involvement of tetrazolyl fragments in multiple hydrogen bonding giving 2D and 1D supramolecular frameworks. Reactivity of the new ligands with different metal salts indicates good coordinating ability, and we report the preparation and structural characterization of the tris–chelate complex [Fe(HL1)3]3− (1) and the homometallic 2D CP [ZnL2(DMSO)] (2). In compound 1 only the diketonate donor is used, whereas the partially deprotonated tetrazolyl groups are involved in hydrogen bonding, giving rise to a 2D supramolecular framework of (6,3)IIa topological type. In compound 2 the ligand is completely deprotonated and uses both the diketonate donor (chelating) and the tetrazolate fragment (bridging) to coordinate the Zn(II) ions. The resulting neutral 2D network of sql topology shows luminescence in the solid state, which is red shifted with respect to the free ligand. Interestingly, it can be easily exfoliated in water to give a luminescent colloidal solution.

A 5-(2-Pyridyl)tetrazolate Complex of Molybdenum(VI), Its Structure, and Transformation to a Molybdenum Oxide-Based Hybrid Heterogeneous Catalyst for the Epoxidation of Olefins

There is a considerable practical interest in discovering new ways to obtain organomolybdenum heterogeneous catalysts for olefin epoxidation that are easier to recover and reuse and display enhanced productivity. In this study, the complex salt (H2pytz)[MoO2Cl2(pytz)] (1) (Hpytz = 5-(2-pyridyl)tetrazole) has been prepared, structurally characterized, and employed as a precursor for the hydrolysis-based synthesis of a microcrystalline molybdenum oxide/organic hybrid material formulated as [MoO3(Hpytz)] (2). In addition to single-crystal X-ray diffraction (for 1), compounds 1 and 2 were characterized by FT-IR and Raman spectroscopies, solid-state 13C{1H} cross-polarization (CP) magic-angle spinning (MAS) NMR, and scanning electron microscopy (SEM). Compounds 1 and 2 were evaluated as olefin epoxidation catalysts using the model reaction of cis-cyclooctene (Cy8) with tert-butyl hydroperoxide (TBHP), at 70 °C, which gave 100% epoxide selectivity up to 100% conversion. While 1 behaved as a homogeneous catalyst, hybrid 2 behaved as a heterogeneous catalyst and could be recovered for recycling without showing structural degradation or loss of catalytic performance over consecutive reaction cycles. The substrate scope was broadened to monoterpene DL-limonene (Lim) and biobased unsaturated fatty acid methyl esters, methyl oleate (MeOle), and methyl linoleate (MeLin), which gave predominantly epoxide products.

DNA profiling and in vitro cytotoxicity studies of tetrazolo[1,5-a]pyrimidine-based copper(II) complexes

A series of N-benzoylated mononuclear copper(II) complexes of the type [Cu(L^1-6)Cl₂] (1-6), where L¹= ethyl 4-benzoyl-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L²= ethyl 4-(4-nitrobenzoyl)-5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L³ = ethyl 4-benzoyl-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁴ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-methoxyphenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate, L⁵ = ethyl 4-benzoyl-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate and L⁶ = ethyl 4-(4-nitrobenzoyl)-5-methyl-7-(4-chlorophenyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylate have been synthesized and characterized by spectral methods. Electron paramagnetic resonance spectra of complexes show four lines, characteristic of square planar geometry. The binding studies of the complexes with calf thymus DNA (CT-DNA) revealed groove mode of binding, which were further supported by molecular docking studies. Gel electrophoresis experiments demonstrated the ability of the complexes to cleave plasmid DNA in the absence of activators. Further, the cytotoxicity activity of the complexes were examined on three cancerous cell lines (lung (A549), cervical (HeLa) and colon (HCT-15)), and on two normal cells (human embryonic kidney (HEK) and peripheral blood mononuclear cells (PBMC)) by MTT assay.

DNA binding, molecular docking and apoptotic inducing activity of nickel(ii), copper(ii) and zinc(ii) complexes of pyridine-based tetrazolo[1,5-a]pyrimidine ligands

The biological activity of metal(ii) complexes of tetrazolo[1,5-a]pyrimidine ligands show that the copper(ii) complexes may act as promising anticancer agents.