Nickel tetrazolato complexes synthesized by microwave irradiation: Catecholase like activity and interaction with biomolecules

Microwave-Assisted Synthesis: Can Transition Metal Complexes Take Advantage of This “Green” Method?

Microwave-assisted synthesis is considered environmental-friendly and, therefore, in agreement with the principles of green chemistry. This form of energy has been employed extensively and successfully in organic synthesis also in the case of metal-catalyzed synthetic procedures. However, it has been less widely exploited in the synthesis of metal complexes. As microwave irradiation has been proving its utility as both a time-saving procedure and an alternative way to carry on tricky transformations, its use can help inorganic chemists, too. This review focuses on the use of microwave irradiation in the preparation of transition metal complexes and organometallic compounds and also includes new, unpublished results. The syntheses of the compounds are described following the group of the periodic table to which the contained metal belongs. A general overview of the results from over 150 papers points out that microwaves can be a useful synthetic tool for inorganic chemists, reducing dramatically the reaction times with respect to traditional heating. This is often accompanied by a more limited risk of decomposition of reagents or products by an increase in yield, purity, and (sometimes) selectivity. In any case, thermal control is operative, whereas nonthermal or specific microwave effects seem to be absent.

Preparation of Tris-Tetrazole-Based Metallogels and Stabilization of Silver Nanoparticles: Studies on Reduction Catalysis and Self-Healing Property

An ionic multifunctional gelator molecule triethylammonium 5-(3,5-bis((1H-tetrazol-5-yl)carbamoyl)benzamido)tetrazol-1-ide G7 is synthesized and characterized by spectroscopic tools and mass spectrometry. G7 tends to form a stable organogel in a mixture of N,N-dimethylformamide/dimethylsulfoxide (DMF/DMSO) and water. Introduction of different metal perchlorate salts in a DMSO solution of G7 furnished a series of metallogels M¹G7, M²G7, M³G7, M⁴G7, M⁵G7, M⁶G7, and M⁷G7 [M¹ = Fe(III), M² = Co(II), M³ = Cu(II), M⁴ = Zn(II), M⁵ = Ag(I), M⁶ = Ni, and M⁷ = Fe(II)]. Among them, M¹G7, M³G7, M⁴G7, M⁶G7, and M⁷G7 help individually in the synthesis and stabilization of bimetallic nanocomposites containing silver nanoparticles (AgNPs). Iron(III)-containing nanocomposites M¹G7AgNPs have been utilized in the form of catalysts in the reduction reaction of nitroaromatic compounds to corresponding amines with a quantitative yield. The organogel G7 has also shown the abilities to absorb different metal ions from aqueous solutions and allow selective transition of M¹G7 from the gel state to the crystalline state. Fe(III) formed dual metallogels with Zn(II), which can be used for further applications. Furthermore, the nanocomposite M¹G7AgNP powder, in the presence of the organogel G7, gets converted into a nanostructured metallogel, which shows exclusive self-healing properties. This is the first example where a nanocomposite powder contains the dual-metal system (Fe(III) and Ag(0)) and shows a reduction catalytic property, and its nanostructured dual-metallogel form manifests the self-healing property in a fabricated metallogel.

Selective anticancer activities of ruthenium(II)-tetrazole complexes and their mechanistic insights

Ruthenium-based metallotherapeutics is an interesting alternative for platinum complexes acting as anticancer agents after the entry of KP1019, NAMI-A, and TLD1339 in clinical trials. Herein, we have synthesized three new arene ruthenium(II)-tetrazole complexes viz. [Ru₂(η⁶-p-cymene)₂(2-pytz)₂Cl₂] (1), [Ru₂(η⁶-p-cymene)₂(3-pytz)Cl₃] (2), [Ru₂(η⁶-p-cymene)₂(4-pytz)Cl₃] (3) [2-pytzH = 2-pyridyl tetrazole; 3-pytzH = 3-pyridyl tetrazole; 4-pytzH = 4-pyridyl tetrazole] which have been characterized by different analytical techniques. To aid the understanding of the complex formation, reactions of the arene ruthenium(II) dimer with tetrazoles were investigated using the first principles-based Density Functional Theory (DFT) B3LYP method. Electronic structures, equilibrium geometries of the reactants and products with the first-order saddle points, reactions mechanism, the changes of enthalpy (∆H) and free energy (∆G), chemical stability, and reaction barriers of the complexes were computed using the B3LYP DFT approach. The in vitro cytotoxicity of these complexes was investigated by MTT assay on different cancer cell lines which reveal complex 2 as the most significant cytotoxic agent toward the HeLa cell line. The complexes have also shown a strong binding affinity towards CT-DNA and albumin proteins (HSA and BSA) as analyzed through spectroscopic techniques. Investigation of the mechanism of cell death by complex 2 was further performed by various staining techniques, flow cytometry, and gene expression analysis by RT-PCR. Inhibition of cell migration study has been also revealed the possibility of complex 2 to act as a prospective anti-metastatic agent.