Synthesis, characterization and biological activity of transition metal complexes with Schiff bases derived from 2-nitrobenzaldehyde with glycine and methionine

Biological and computational investigation of transition metal(II) complexes of 2-phenoxyaniline-based ligands

Aim: In the 21st century, we are witness of continuous onslaughts of various pathogen deformities which are a major cause of morbidity and mortality worldwide. Therefore, to investigate the grave for these deformities, antioxidant, anti-inflammatory and antimicrobial biological activities were carried out against newly synthesized Schiff base ligands and their transition metal complexes, which are based on newly synthesized 2-phenoxyaniline and salicylaldehyde derivatives. Materials & methods: The synthesized compounds were characterized by various physiochemical studies, demonstrating the octahedral stereochemistry of the complexes. Results: The biological assessments revealed that complex 6 (3.01 ± 0.01 μM) was found to be highly active for oxidant ailments whereas complex 14 (7.14 ± 0.05 μM, 0.0041-0.0082 μmol/ml) was observed as highly potent for inflammation and microbial diseases. Conclusion: Overall, the biological and computational studies demonstrate that the nickel(II) complex 14 can act as an excellent candidate for pathogen deformities.

Medicinal applications of vanadium complexes with Schiff bases

Many transition metal complexes have been explored for their therapeutic properties after the discovery of cisplatin. Schiff bases have an efficient complexation tendency with the transition metals and several medicinal properties have been reported. However, fewer studies have reported the medicinal utility of vanadium and its Schiff base complexes. This paper provides a comprehensive overview of vanadium complexes with Schiff bases along with their mechanistic insight. Vanadium complexes in + 4 and + 5 oxidation states have exhibited well-defined geometry and found to be thermodynamically stable. The studies have reported the G0/G1 phase cell cycle arrest and decreased delta psi m, inducing mitochondrial membrane depolarization in cancer cell lines along with the alterations in the metabolism of the cancer cells upon dosing with the vanadium complexes. Cancer cell invasion and growth are also found to be markedly reduced by peroxo complexes of vanadium. The studies included in the review paper have been taken from leading indexing databases and focus was laid on recent reports in literature. The biological potential of vanadium complexes of Schiff bases opens new horizons for future interdisciplinary studies and investigation focussed on understanding the biochemistry of these complexes, along with designing new complexes which have better bioavailability, solubility and low or non-toxicity.

Bovine serum albumin interaction, molecular docking, anticancer and antimicrobial activities of Co(II) Schiff base complex derived from Nophen ligand

In this report, synthesis, characterization, biological and molecular modeling studies of Nophen Schiff base [N,N-bis(2-hydroxy-1-naphthaldehyde)-o-phenylenediamine] and Co(II)-Nophen complex have been furnished. BSA binding affinities of the ligand and Co(II)-Nophen complex have been appraised by UV-visible, fluorescence and cyclic voltammetric techniques. Spectroscopic measurements indicate strong binding of the complex with BSA protein through static quenching mechanism with binding constant in the order of 10⁴ M^-1. The negative shift of the peak potential in cyclic voltammetry suggested an electrostatic interaction. Molecular docking analysis reveals significant binding affinity (-6.3 kcal/mol) of the complex towards BSA protein. It is amazing that the in vitro cytotoxicity of Co(II)-Nophen complex against A549 cell lines (Human lung carcinoma cells) has remarkable potentials with 29 ± 1.2 µM as IC₅₀ value. Comparing the biological activity towards microorganisms, Co(II)-Nophen complex show substantial response than the Nophen ligand.Communicated by Ramaswamy H. Sarma.

Biological and molecular modeling studies on some transition metal(II) complexes of a quinoxaline based ONO donor bishydrazone ligand

In this report, synthesis, characterization, biological and molecular modeling studies of an ONO donor tridentate bishydrazone ligand, 3-[N'-(2-Hydroxy-3-methoxy-benzylidene)-hydrazino]-1H-quinoxalin-2-one (HHQ) and its 1:1 mononuclear Co(II) (HHQ-1), Ni(II) (HHQ-2), Cu(II) (HHQ-3) and Zn(II) (HHQ-4) complexes have been conferred. Octahedral geometry was assigned to HHQ-1, HHQ-2 and HHQ-4 and distorted octahedral geometry for HHQ-3. The lattice parameters, morphology and electrochemical behaviors of the compounds were studied by powder XRD, SEM and cyclic voltammetry analyses respectively. The antimicrobial assays were carried out against the bacterial (Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa) and fungal (Aspergillus flavus, Aspergillus niger and Candida albicans) strains. Furthermore, the DNA binding, cleaving and superoxide dismutase (SOD) activities of HHQ and its metal(II) complexes were discussed. The structures of HHQ and its derivatives were optimized by DFT techniques. Using molecular docking the molecular interaction dynamics amongst the DNA and SOD with HHQ and its metal(II) complexes were recognized.Communicated by Ramaswamy H. Sarma.

Sulfamerazine Schiff-base complex intercalated layered double hydroxide: synthesis, characterization, and antimicrobial activity

Cobalt (Co(II)) and copper (Cu(II)) complexes of sulfamerazine-salicylaldehyde (SS) ligand intercalated Mg/Al-layered double hydroxide [Co-SS-LDH/Cu-SS-LDH] were prepared for the antimicrobial application. Sulfamerazine and salicylaldehyde were mixed together and dissolved in methanol for the synthesis of SS ligand and modified further by the complexation with Co(II) and Cu(II) metal ions [Co-SS/Cu-SS]. The delaminating/restacking method was used to intercalate the Mg/Al-NO₃-LDH with the metal complexed ligands (Co-SS/Cu-SS). The obtained materials were analyzed using different characterization techniques to prove their successful synthesis and preparation. The antibacterial activity of the synthesized Co-SS-LDH/Cu-SS-LDH were checked by the inhibition zone method. The prepared hybrid materials showed good antimicrobial activity against both gram negative (Escherichia coli, E. coli) and gram positive (Staphylococcus aureus, S. aureus) bacteria.

Synthesis, spectral characterization, DNA interaction, anticancer and molecular docking studies on some transition metal complexes with bidentate ligand

The ligand, N(2),N(3)-bis(3-nitrophenyl)quinoxaline-2.3-diamine was prepared by the condensation of quinoxaline-2.3(1,4H)-dione with 3-nitroaniline. It was treated with Co(II), Ni(II), Cu(II) and Zn(II) acetates to form the metal complexes. These were characterized by elemental analysis, molar conductance, magnetic moment, UV-Vis., IR, (1)H NMR, ESR and mass spectral data. Octahedral geometry has been assigned to Co(II), Ni(II) and Zn(II) complexes, whereas Cu(II) complex has distorted octahedral geometry. From the powder XRD data, crystallite size and unit cell parameters were calculated. The surface morphology of the synthesized compounds were determined using SEM analysis. The antimicrobial activity of the compounds against some bacterial species viz. Escherichiacoli, Klebsiella pneumoniae, Pseudomonas aeuruginosa and Staphylococcus aureus; also the fungal species, Aspergillus niger, and Candida albicans were done by disc diffusion method. DNA binding, cleavage and super oxide anion scavenging activities were also evaluated. The DNA binding activity of the compounds were identified using electronic absorption titrations and DNA cleavage was determined using gel electrophoresis. The anticancer activities of the compounds against HeLa cell line were determined using MTT assay. The highly potent compound among the five against HeLa cell line is subjected to molecular docking study against human papilloma virus receptor molecule and ATP binding site of telomerase.

Bio-relevant complexes of novel N2O2 type heterocyclic ligand: Synthesis, structural elucidation, biological evaluation and docking studies

Organic and inorganic entities [Cu(II), Co(II), Ni(II) and Zn(II)] have been bridged by N2O2 type heterocyclic imine (CN) ligand for the synthesis of novel organic-inorganic bridged complexes of the type [M(H2L)]. The synthesized complexes were characterized by spectral techniques such as FT-IR, UV-visible, (1)H NMR, (13)C NMR, EPR, ESI-Mass, elemental analysis, magnetic susceptibility and molar conductivity measurements. The metal complexes adopt square planar geometrical arrangement around the metal ions. DNA binding ability of these complexes has been explored by different techniques viz. electronic absorption, fluorescence, cyclic voltammetry, differential pulse voltammetry and viscosity measurements. These studies prove that CT DNA interaction of the complexes follows intercalation mode. The oxidative cleavage of the complexes with pUC19 DNA has been investigated by gel electrophoresis. Molecular docking calculations have been performed to understand the nature of binding of the complexes with DNA. Moreover, the anti-pathogenic actions of the complexes were tested in vitro against few bacteria and fungi by disk diffusion method. The data reveal that the complexes have higher anti-pathogenic activity than the ligand.

Silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases-Novel noncompetitive α-glucosidase inhibitors

A series of silver(I) complexes of 2,4-dihydroxybenzaldehyde-amino acid Schiff bases were designed and tested for α-glucosidase inhibition. Our results indicate that all the silver complexes (4a-18a) possessed strong inhibitory activity at μmolL(-1) level, especially glutamine (12a) and histidine (18a) Schiff base silver(I) complexes exhibited an IC50 value of less than 0.01μmolL(-1). This series of compounds exhibited noncompetitive inhibition characteristics in kinetic studies. In addition, we investigated the mechanism of inhibition and the structure-activity relationships of the amino acid Schiff base silver complexes. Our results reveal that Schiff base silver complexes may be explored for their therapeutic potential as alternatives of α-glucosidase inhibitors.

Synthesis of new microbial pesticide metal complexes derived from coumarin-imine ligand

A series of metal complexes of zinc(II), cadmium(II), copper(II), nickel(II) and palladium(II) have been synthesized from coumarin-imine ligand, 8-[(1E)-1-(2-aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate, [HL]. The structures of the complexes were proposed in the light of their spectroscopic, molar conductance, magnetic and thermal studies. The ligand coordinated in a tridentate manner through the azomethine nitrogen, the phenolic oxygen and the amine nitrogen and all complexes were non-electrolytes with different geometrical arrangements around the central metal ion. Photoluminescence data unambiguously showed remarkable fluorescence enhancement to Zn(2+) over other cations. The antimicrobial screening tests revealed that copper(II) complex exhibited the highest potency and its minimum inhibitory concentration on the enzymatic activities of the tested microbial species was determined. No toxin productivity was detected for all tested toxigenic species upon the exposure of copper complex.

Antimicrobial efficacy of phenanthrenequinone based Schiff base complexes incorporating methionine amino acid: structural elucidation and in vitro bio assay

This work focuses the synthesis and characterization of few novel mixed ligand Schiff base metal complexes and their biological activities. For deriving the structural aspects, spectral techniques such as FT-IR, UV-Vis., (1)H NMR, Raman, EPR and the physicochemical characterizations including elemental analysis, molar conductance and magnetic susceptibility method have been involved. All the complexes adopt square planar geometry. DNA binding ability of these complexes has been explored using diverse techniques viz. UV-Vis. absorption, fluorescence spectroscopy, viscometry and cyclic voltammetry. These studies prove that CT-DNA binding of the complexes follows the intercalation mode. Comparative DNA oxidative cleavage ability of the complexes has been done under ultraviolet photo radiation on pUC19 DNA. In addition, the biocidal action of the complexes has been investigated against few pathogenic bacteria and fungi by disc diffusion method. Importantly, the amylase inhibition activity of Cu(II) complex has been explored. The amylase inhibition property has been found to be increased upon increasing the complex concentration.

Spectral characterization and 3D molecular modeling studies of metal complexes involving the O, N-donor environment of quinazoline-4(3H)-one Schiff base and their biological studies

A simple condensation of 3-amino-2-methylquinazoline-4-one with 2-hydroxy-1-naphthaldehyde produced new tridentate ONO donor Schiff base ligand with efficient yield. The structural characterization of ligand and its Cu(II), Ni(II), Co(II), Mn(II), Zn(II), and Cd(II) complexes were achieved by the aid of elemental analysis, spectral characterization such as (UV-visible, IR, NMR, mass, and ESR), and magnetic data. The analytical and spectroscopic studies suggest the octahedral geometries of Cu(II), Co(II), Ni(II) and Mn(II) complexes and tetrahedral geometry of Zn(II) and Cd(II) complexes with the tridentate ONO Schiff base ligand. Furthermore, the conclusions drawn from these studies afford further support to the mode of bonding discussed on the basis of their 3D molecular modeling studies by considering different bond lengths, bond angles, and bond distance. The ligand and its metal complexes evaluated for their antimicrobial activity against Staphylococcus aureus (MTCC number 7443), Bacillus subtilis (MTCC number 9878), Escherichia coli (MTCC number 1698), Aspergillus niger (MTCC number 281), and Aspergillus flavus (MTCC number 277). The MIC of these compounds was found to be most active at 10 μ g/mL concentration in inhibiting the growth of the tested organisms. The DNA cleavage activity of all the complexes was studied by gel electrophoresis method.

Spectroscopic and density functional theory investigation of novel Schiff base complexes

Novel Schiff base (H(2)L, 1,2-bis[(2-(2-mercaptophenylimino)methyl)phenoxy] ethane) derived from condensation of bisaldehyde and 2-aminothiophenol was prepared in a molar ratio 1:2. The ligand and its metal complexes are fully characterized with analytical and spectroscopic techniques. The metal complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II) and Th(IV) have been prepared and characterized by elemental analyses, IR and (1)H-NMR spectroscopy, thermal and magnetic measurements. The results suggested that the Schiff base is a bivalent anion with hexadentate OONNSS donors derived from the etheric oxygen (O, O'), azomethine nitrogen (N, N') and thiophenolic sulphur (S, S'). The formulae of the complexes were found to be [ML]·xH(2)O (M=Mn(II) (x=0), Co(II) (x=1), Ni(II), (x=1), Cu(II) (x=2) and Zn(II) (x=0)) and [ML]·nCl (M=Cr(III) (n=1), Fe(III) (n=1) and Th(IV) (n=2)). The thermogravimetric analysis of the complexes shows metal oxide remaining as the final product at 700-1000 °C. Density functional theory at the B3LYP/6-31G(*) level of theory was used to investigate molecular geometry, Mulliken atomic charges and energetics. The synclinal-conformer was found to be responsible for complex formation. The calculation showed that ligand has weak field. Structural deformation and the dihedral angles rotation during complexation were investigated. The binding energy of each complex was calculated. The calculated results are in good agreement with experimental data.