Synthesis, Spectroscopic Characterization, and Biological Evaluation Studies of 5-Bromo-3-(((hydroxy-2-methylquinolin-7-yl)methylene)hydrazono)indolin-2-one and Its Metal (II) Complexes

Abstract

The Schiff base ligand 5-bromo-3-(((8-hydroxy-2-methylquinolin-7-yl)methylene)hydrazono)indolin-2-one (BHMQMHI) was prepared via condensation of 5-bromo-3-hydrazonoindolin-2-one and 7-formyl-8-hydroxy-2-methylquinoline and its Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) complexes have been synthesized and characterized by elemental analysis, conductance data, magnetic susceptibility measurements, IR, UV-Vis, mass spectrometry, 1H NMR, ESR, XRD, and thermal studies. By these spectral studies it is found that Co(II), Ni(II), and Cu(II) complexes have exhibited octahedral geometry whereas the Zn(II), Cd(II), and Hg(II) complexes have exhibited tetrahedral geometry. Potentiometric studies have been carried out on complexes of Schiff base (BHMQMHI) with Cu(II), Co(II), and Ni(II). Calvin-Bjerrum pH-titration technique as used by Irving and Rossotti has been applied to determine stability constants in mixed solvents at 25 ± 1°C. The present study reports the protonation constants of this ligand and stability constants of its metal complexes in dioxane-water (50%, v/v) mixtures. Metal-ligand stability constants fall in the order of Cu(II) > Co(II) > Ni(II) which is in agreement with those reported by Irving stability order. The Schiff base (BHMQMHI) and its metal complexes have been screened for their in vitro antibacterial and antifungal activities by minimum inhibitory concentration (MIC) method. The DNA cleavage activities of all the complexes were studied by agarose gel electrophoresis method. In addition, the free ligand along with its complexes has been studied for their antioxidant activity.

Cu(II) Complexes of 4-[(1E)-N-{2-[(Z)-Benzylidene-amino]ethyl}ethanimidoyl]benzene-1,3-diol Schiff Base: Synthesis, Spectroscopic, In-Vitro Antioxidant, Antifungal and Antibacterial Studies

“…This was further supported by the downward shift in the phenolic ν(C−O) group observed at 1266 cm −1 in the free ligand to the region 1237–1246 cm −1 [ 22 ] upon complexation. This shift confirms the coordination of the phenolate oxygen to the metal ion [ 14 , 20 ].…”

“…The infrared of BEB displayed characteristic bands at 3404 cm −1 that could be attributed to the ν(O‒H) stretching vibrations in the free Schiff ligand [ 10 , 16 ]. The absence of this band in the spectra of the complexes is an indication of deprotonation and involvement of the phenolic hydroxyl group of the ligand during bond formation with the copper ions [ 19 , 20 ]. The medium and broadband at 3378–3396 cm −1 in the spectra of the Schiff base-Cu(II) complexes are assigned to the ν(OH) frequency of the water molecules in the complexes [ 21 ].…”

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“…This indicated the involvement of N-atom of the azomethine (-HC=N) group and carbonyl oxygen in complex formation 10,11 and the band at 3207, 1606 cm -1 in the spectra of all the complexes were assigned to ν(N-H) and ν(C=N) of the ketimine moiety remain almost unaffected, indicating the non participation of these groups in coordination. 12 Therefore, the IR spectral data indicated that the coordination of hydrazone Schiff base to metal ion occurred through the N-atom of the azomethine (-C=N) group and the O-atom of carbonyl (C=O) group. Assignment of the proposed coordination sites was further supported by the appearance of medium bands at 453-499 cm -1 and 351-379 cm -1 due to M-N and M-Cl stretching frequencies, respectively.…”

Synthesis, Characterization and Biological Approach of N’-(3-(Hydroxy Imino) Butan-2-ylidene)-2-Oxo-2H-Chromene-3-Carbohydrazide Complexes

“…Constructed on the ''MEP'' , one can mostly order the electron-rich area with has red color of a map which prefer site for electrophilic attack. However, the electron-poor region has blue color favors site for nucleophilic attack [30]. Nevertheless, the green region point to neutral electrostatic potential region.…”