SYNTHESIS AND SOLVATOCHROMIC BEHAVIOUR OF SOME HETEROCYCLYIC ISONICOTINOHYDRAZIDE SCHIFF BASES

The solvatochromic behaviour of three heterocyclic Schiff bases derived from isonicotinic acid hydrazide (INH) and pyrrole-2-carboxaldehyde (L1), furan-2-carboxaldehyde (L2) and thiophene-2-carboxaldehyde (L3) was studied in nine solvents of different polarities.  The electronic transition properties were investigated using the Kamlet-Taft parameters, dielectric function, refractive index function and Catalan parameters.   The results indicate that the hydrogen bond acceptor properties of the solvent are more effective in directing the solvatochromic behavior of the Schiff bases.

Synthesis, spectroscopic and antimicrobial properties of Co(II), Ni (II) and Cu(II) complexes of (E)-N’-(2-hydroxy -5-nitrobenzylidene)isonicotinohydrazide)

The objective of this study is to investigate the antimicrobial activity of novel Schiff base metal complexes. The resistance of micro-organisms to classical antimicrobial compounds poses a challenge to effective management and treatment of some diseases. In line with this, copper (II), nickel (II) and cobalt (II) complexes of the Schiff base ligand (E)-N’-(2- hydroxy-5-nitrobenzylidene) isonicotinohydrazide) were synthesized and characterized based on elemental analysis, conductivity measurements, infrared and electronic absorption spectroscopy. The results suggest a 1:2 [M:L] stoichiometry for the copper and cobalt complexes and a 1:1 [M:L] ratio for the nickel complex. The electronic absorption spectral data support octahedral geometry for cobalt(II) and copper(II) complexes and square planar for nickel (II). In-vitro antimicrobial properties of the compounds evaluated against five pathogenic bacteria using the agar-well diffusion method revealed that the activity was in the order Ni>Co>Cu. These compounds can be used as substrates for development of new antimicrobial agents.Keywords: isonicotinohydrazide, Schiff base metal complexes, in-vitro, antimicrobial activity, electronic spectra, 2-hydroxy-5-nitrobenzaldehyd

Synthesis, structural, DFT calculations and biological studies of rhodium and iridium complexes containing azine Schiff-base ligands

The reaction of [Cp*MCl2]2 (M = Rh/Ir) with N-Nʹ azine Schiff-base ligands (L1-L4) leads to the formation of mononuclear cationic half-sandwich complexes having the general formula [Cp*M(L)Cl]+ (1–8), (M = Rh/Ir and L = (2-hydroxy-4-methoxybenzylidene)2- pyridylamidrazone (L1), (2-hydroxybenzylidene)2-pyridylamidrazone (L2), (1-(2-hydroxyphenyl)ethylidene)2-pyridylamidrazone (L3) and (1-phenylethylidene)2-pyridylamidrazone (L4). All these complexes were isolated as their hexafluorophosphate salts and fully characterized by spectroscopic and analytical techniques. The molecular structure of complexes (1), (3), (4), (7) and (8) have been determined by single crystal X-ray crystallographic studies which displayed the coordination of the ligand to the metal in a bidentate N∩N fashion through nitrogen atom of pyridine and one azine nitrogen. The chemo-sensitivity activities of the complexes were evaluated against HT-29 (human colorectal cancer) cell line and non-cancer cell line ARPE-19 (human retinal epithelial cells) which revealed that the complexes are moderately cytotoxic to cancer cells over human cells although complex 5 was the most potent among all the compounds. Theoretical studies carried out using DFT and TD-DFT at B3LYP level shows good agreement with the experimental results

Metal complexes of 4-aminopyridine Schiff bases: Potent molecules in the design of anti-tuberculosis agents

Communication in Physical Sciences, 2023, 9(3):203-212 Authors: Dueke-Eze, Cordelia U., Fasina, Tolulope M. and Familoni, Oluwole B. Received: 10 February 2023/Accepted 20 May 2023 Tuberculosis (TB)  has remained a serious public health challenge and one of the most prevalent causes of death regarding infectious diseases, despite decades of relentless drug development research. The resurgence of TB is due to its prevalence in synergy with the AIDS epidemic and the rise of multidrug-resistant (MDR) TB. Therefore, finding new, effective bioactive agents to manage and treat the disease is a top priority. To discover a new and effective chemotherapeutic agent for the treatment of TB, Cu(II), Ni(II) and Co(II) complexes of 4-aminopyridine-based Schiff bases have been synthesized, characterized based on melting point, elemental analyses, FT-IR, NMR, UV-vis and molar conductance. The spectra revealed that the Schiff base ligands act as a bidentate ligand through the azomethine nitrogen atom and a phenolic oxygen atom. The molar conductance measurements of the complexes in DMF correspond to non-electrolytic nature. The antituberculosis activity of the compounds using the proportion method revealed that the nitro-containing Cu(II) and Co(II) complexes exhibited enhanced in vitro antituberculosis activity compared with the ligands and reference compound (INH) at 0.1 μg/ml