Recent developments in penta-, hexa- and heptadentate Schiff base ligands and their metal complexes

Vanadium as an important national strategy resource is widely used in many fields due to its excellent physicochemical properties. Much attention had been focused on recovering vanadium from vanadium titano-magnetite and stone coal as they were the main vanadium resources in China. Sodium roasting technology was the earliest technology applied in recovering vanadium, high recovery efficiency of vanadium was obtained along with serious environment problem like corrosive gases and hazardous wastewater. Calcium roasting technology avoided above problems, but high energy-cost and low recovery was remained. Non-salt roasting technology was suitable for limited vanadium resource. Vanadium was leached out after roasting and the leaching medium was divided into three parts according to the roasting technology. Recover process of vanadium depended on the vanadium species and pH in the leaching solution. Hydrolysis was the easily technology with most impurities. Ammonium precipitation was the common process for every technology. And high purity of V2O5 was obtained by calcining precipitation of recovery process. Overall, the industry of vanadium leaching was still underdeveloped, and much intensive research work was needed.

A literature review on leaching and recovery of vanadium

Cancer is one of the leading causes of death worldwide. Although several potential therapeutic agents have been developed to efficiently treat cancer, some side effects can occur simultaneously. Papaverine, a non-narcotic opium alkaloid, is a potential anticancer drug that showed selective antitumor activity in various tumor cells. Recent studies have demonstrated that metal complexes improve the biological activity of the parent bioactive ligands. Based on those facts, herein we describe the synthesis of novel papaverine-vanadium(III), ruthenium(III) and gold(III) metal complexes aiming at enhancing the biological activity of papaverine drug. The structures of the synthesized complexes were characterized by various spectroscopic methods (IR, UV-Vis, NMR, TGA, XRD, SEM). The anticancer activity of synthesized metal complexes was evaluated in vitro against two types of cancer cell lines: human breast cancer MCF-7 cells and hepatocellular carcinoma HepG-2 cells. The results revealed that papaverine-Au(III) complex, among the synthesized complexes, possess potential antimicrobial and anticancer activities. Interestingly, the anticancer activity of papaverine-Au(III) complex against the examined cancer cell lines was higher than that of the papaverine alone, which indicates that Au-metal complexation improved the anticancer activity of the parent drug. Additionally, the Au complex showed anticancer activity against the breast cancer MCF-7 cells better than that of cisplatin. The biocompatibility experiments showed that Au complex is less toxic than the papaverine drug alone with IC50 ≈ 111 µg/mL. These results indicate that papaverine-Au(III) complex is a promising anticancer complex-drug which would make it a suitable candidate for further in vivo investigations.

https://www.mdpi.com/1420-3049/25/22/5447/pdf

Novel Papaverine Metal Complexes with Potential Anticancer Activities.

Adsorption studies were carried out on a red mud modified sawdust biochar material to assess its capacity in the removal of vanadium (V) from aqueous solution. In this study, a number of parameters which can potentially influence V(V) adsorption were investigated including equilibrium V(V) solution concentration, contact time for effective V(V) removal, temperature of the adsorption process, solution pH and ionic strength. The uptake of V(V) was shown to be heavily influenced by solution pH with maximum uptake (16.45 mg g−1) achieved in the pH range of 3.5 - 5.5. The adsorption process was best described by the Langmuir model. The kinetics of the adsorption process indicated that V(V) uptake occurred within 60 min of contact and that pseudo-second order kinetics best described the kinetics of the overall adsorption process. There was a clear increase in V(V) uptake with increasing temperature (range 293–343 K) indicating an endothermic adsorption process and the level of uptake remained largely unchanged at solution salt concentrations of up to 0.1 M NaCl and competing cation concentrations of up to 2000 mg L-1 of sodium and 200 mg L-1 aluminium. The relatively weak interaction between V(V) and the modified biochar surface may indicate a possibility of recovery of the bound V(V) and subsequent regeneration of the adsorbent.

Removal of vanadium from aqueous solution using a red mud modified saw dust biochar

Cytosine, a DNA and RNA building-block, and Metformin, the most widely prescribed drug for the treatment of Type 2 Diabetes mellitus were made to react separately with ammonium or sodium metavanadates in acidic aqueous solutions to obtain two polyoxovanadate salts with a 6:1 ratio of cation-anion. Thus, compounds [HCyt]6[V10O28]·4H2O, 1 and [HMetf]6[V10O28]·6H2O, 2 (where HCyt = Cytosinium cation, [C4H6N3O]+ and HMetf = Metforminium cation, [C4H12N5]+) were obtained and characterized by elemental analysis, single crystal X-ray diffraction, vibrational spectroscopy (IR and Raman), solution 51V-NMR, thermogravimetric analysis (TGA-DTGA), as well as, theoretical methods. Both compounds crystallized in P 1 ¯ space group with Z' = 1/2, where the anionic charge of the centrosymmetric ion [V10O28]6- is balanced by six Cytosinium and six Metforminium counterions, respectively. Compound 1 is stabilized by π-π stacking interactions coming from the aromatic rings of HCyt cations, as denoted by close contacts of 3.63 A. On the other hand, guanidinium moieties from the non-planar HMetf in Compound 2 interact with decavanadate μ2-O atoms via N-H···O hydrogen bonds. The vibrational spectroscopic data of both IR and Raman spectra show that the dominant bands in the 1000-450 cm-1 range are due to the symmetric and asymmetric ν(V-O) vibrational modes. In solution, 51V-NMR experiments of both compounds show that polyoxovanadate species are progressively transformed into the monomeric, dimeric and tetrameric oxovanadates. The thermal stability behavior suggests a similar molecular mechanism regarding the loss of water molecules and the decomposition of the organic counterions. Yet, no changes were observed in the TGA range of 540-580°C due to the stability of the [V10O28]6- fragment. Dispersion-corrected density functional theory (DFT-D) calculations were carried out to model the compounds in aqueous phase using a polarized continuum model calculation. Optimized structures were obtained and the main non-covalent interactions were characterized. Biological activities of these compounds are also under investigation. The combination of two therapeutic agents opens up a window toward the generation of potential metalopharmaceuticals with new and exciting pharmacological properties.

/pdf/decavanadate-salts-of-cytosine-and-metformin-a-combined-4o8n9wcucj.pdf

Valentina Villalobos Coa

Papers

Vanadium: History, chemistry, interactions with α-amino acids and potential therapeutic applications.

Relationship between Structure and Odor