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.

Unfortunately, many toxic solvents are used in chemistry laboratories and in the manufacturing of materials, which poses a serious risk to process safety, the natural environment, and human health. In this review, different tools for solvent-free organic reactions have been surveyed as an approach for green chemistry, where many of the solvents are known to upset our ecosystems so an enormous research effort has been exerted during the last decade to avoid the utilization of hazardous solvents and the number of publications on solvent-free reactions has increased nearly exponentially. Obviously, this reflects the great interest in solventless reactions. In our survey, we will highlight the solvent-free organic reaction as an approach for green chemistry to cover work published up to nearly 2022.

A novel Schiff base ligand derived from o-Vanillin, N, N-Diethyl-p-phenylenediamine in 1:1 molar ratio, and its metal complexes of Mn (II), Co (II), Ni (II), Cu (II), Zn (II) and Zr (IV) were synthesized by microwave and conventional methods. The ligand and its complexes were characterized by elemental analysis, FT-IR, UV-Vis, 1HNMR, mass spectroscopy as well as Thermo-Gravimetric Analysis (TGA). The geometry of the proposed Structures of the chelates based on their Electronic spectra, Electron paramagnetic resonance (EPR) and magnetic moment. The thermal dehydration and decomposition of the complexes were studied kinetically using the integral method applying the Coats–Redfern and Horowitz Metzger equation. Study the Variation of magnetic susceptibility at Different temperature for Mn (II) and Co (II) complexes. Surface morphologies were analyzed by Scanning electron microscopy (SEM). The ligand and its metal complexes were screened for antimicrobial activity against Gram-positive, Gram-negative bacteria as well as fungi. Cu (II) complex achieved a brilliant inhibition zone diameter against E. coli almost reached the inhibition zone diameter record by standard positive control Cephalothin making it eligible for treatment of E. coli. Also, Cytotoxicity Evaluation was applied against two cell lines; human colon carcinoma (HCT) and liver cancer cells (HepG-2).