Synthesis, characterization, and thermal and antimicrobial studies of newly developed transition metal-polychelates derived from polymeric Schiff base

Green Synthesis, Characterization, Antimicrobial and Anticancer Screening of New Metal Complexes Incorporating Schiff Base

A Schiff base ligand of o-vanillin and 4-aminoazobenzene and its transition metal complexes of Ni(II), Co(II), Zn(II), Cu(II), Mn(II), and Zr(IV) were prepared under microwave irradiation as a green approach compared to the conventional method. The structures of new compounds have been characterized and elucidated via elemental and spectroscopic analyses. In addition, magnetic susceptibility, electron spin resonance, and electronic spectra of the synthesized complexes explained their geometrical structures. The thermal stability of Cu(II), Zn(II), and Zr(IV) complexes was studied by thermo-gravimetric analyses (TGA). Coats-Redfern and Horowitz-Metzger equations were used to calculate the thermal and dehydration decomposition activities of proposed structures kinetically. Surface morphologies of the solid compounds were imaged by scanning electron microscopy (SEM). The particle size of prepared complexes was measured by using a particle size analyzer at a diffraction angle of 10.9°. The geometry structures of the synthesized compounds were verified utilizing electronic spectra, ESR spectrum, and magnetic moment value. The newly synthesized compounds were screened for antimicrobial activity. Also, the anticancer activity of the free Schiff base ligand and its metal complexes were studied against two cell lines: human colon (HCT-116) and human liver cancer cells (HepG-2). The obtained results showed that the Cu(II) complex displayed the highest cytotoxic activity (IC₅₀ = 18 and 22 μg/mL for HepG-2 and HCT, respectively) compared to the free Schiff base ligand.

Development of a polymeric nanocomposite as a high performance adsorbent for Pb(II) removal from water medium: Equilibrium, kinetic and antimicrobial activity

In the present study, starch based ZnO nancomposite (CSt-ZnO) was synthesized for the efficient removal of Pb(II) ions from aqueous medium. The structure and morphology of CSt-ZnO nancomposite was characterized using SEM, FTIR, TGA, BET, XPS and zeta potential measurements. The effect of contact time, pH, temperature and initial concentration of Pb(II) on the adsorption was studied. The optimum parameters for maximum Pb(II) removal were time-120 min; pH-6; temperature-318 K and C_o-20 ppm. The maximum Langmuir adsorption capacity of CSt-ZnO nancomposite was 256.4 mg/g at 298 K. With increasing the temperature from 298 K to 318 K, the maximum adsorption quantity (q_m) was improved from 256.4 to 476 mg/g which showed the endothermic nature of Pb(II) adsorption on CSt-ZnO nanocomposite. The sorption isotherm and kinetics model fitting studies, confirmed that data fit well to Freundlich isotherm and pseudo-first-order kinetics models, respectively. Thermodynamic studies inferred a spontaneous and endothermic nature of adsorption. Moreover, the adsorption capacity was 68% even after four adsorption-desorption cycles which revealed the reusable performance of CSt-ZnO was well. The antimicrobial activity of CSt-ZnO nanocomposite was also examined against S. aureus and E. coli.

Synthesis, characterization and solid state conductivity of nano-size ionic Schiff base polymers of Cu2+, Zn2+ and VO2+ containing viologen moieties

The new nano size ionic metallo-Schiff base polymers (IMSPs) were synthesized by reaction of Schiff base ligand of L and VO (acac)₂, ZnCl₂ and CuCl₂. The solid state conductivity measurements candidate them as new metallo-organic semiconductors.

Preparation of Schiff Base Derived from 3,4-Dimethoxybenzaldehyde andp-Aminobenzoic Acid by Supersonic Speed Gas Impacting Method

A Schiff base derived from 3,4-dimethoxybenzaldehyde andp-aminobenzoic acid (SBDA) was synthesized by novel supersonic speed gas impacting method. The morphology and geometric structure of the synthesized Schiff base SBDA were investigated, the results showed that the particles of SBDA were not completely regular and the HOMO and LUMO of SBDA optimized geometry structure using the semiempirical method PM3 were −9.115 eV and −1.191 eV, respectively, and some bond length of synthesized SBDA became short and bone angle became large compared to the reactant. The thermogravimetric analysis results indicated that SBDA began to decompose above 280°C; the decomposition temperature and thermogravimetric rate could vary with the different heating rate.

Synthesis, characterization and anti-microbial activity of phenylurea-formaldehyde resin (PUF) and its polymer metal complexes (PUF-Mn(II)

Phenylurea-formaldehyde polymer (PUF) was synthesized via polycondensation of phenylurea and formaldehyde in basic medium, its polymer-metal complexes [PUF-M(II)] were prepared with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) ions. PUF and PUF-M(II) were characterized with magnetic moment measurements, elemental and spectral (UV-visible, FTIR, 1H-NMR, 13C-NMR and ESR) analysis. The thermal behaviors of all the synthesized polymers were carried out using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The thermal data revealed that all of the PUF-M(II) showed higher thermal stabilities than the PUF and also ascribed that the PUF-Cu(II) showed better thermal stability than the other PUF-M(II). The kinetic parameters such as activation energy, pre-exponential factor etc., were evaluated for these polymer metal complexes using Coats-Redfern equation. In addition, the antimicrobial activity of the synthesized polymers was tested against several microorganisms using agar well diffusion methods. Among all of the PUF-M(II), the antimicrobial activity of the PUF-Cu(II) showed the highest zone of inhibition because of its higher stability constant and may be used in biomedical applications.

New thermal and microbial resistant metal-containing epoxy polymers

A series of metal-containing epoxy polymers have been synthesized by the condensation of epichlorohydrin (1-chloro-2,3-epoxy propane) with Schiff base metal complexes in alkaline medium. Schiff base was initially prepared by the reaction of 2,6 dihydroxy 1-napthaldehyde and o-phenylenediamine in 1 : 2 molar ratio and then with metal acetate. All the synthesized compounds were characterized by elemental, spectral, and thermal analysis. The physicochemical properties, viz., epoxy value, hydroxyl content, and chlorine content [mol/100 g] were measured by standard procedures. The antimicrobial activities of these metal-containing epoxy polymers were carried out by using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) methods against S. aureus, B. subtilis (Gram-positive bacteria), and E. coli, P. aeruginosa (Gram-negative bacteria). It was found that the ECu(II) showed higher antibacterial activity than other metal-chelated epoxy resin while EMn(II) exhibited reduced antibacterial activity against all bacteria.