Ni(II), Pd(II) and Pt(II) complexes of (1H-1,2,4-triazole-3-ylimino)methyl]naphthalene-2-ol. Structural, spectroscopic, biological, cytotoxicity, antioxidant and DNA binding

Synthesis and X-ray evaluation of 7 N-1S thiabendazole based 1,2,3-triazole as a dual metal sensing probe: Molecular logic gate construction, DFT analysis, real water sample analysis and catalytic activity investigation of its metal complexes

The research aimed to develop of a thiabendazole-derived dual metal sensing probe (TBZT) for the selective detection of metal ions and to explore its metal complexes in reducing environmental pollutants like nitro-phenol and dyes. Absorption and emission based studies predicted the selectivity and sensitivity of TBZT towards Ni(II) and Co(II) ions which was further validated by 1HNMR, Mass, FT-IR, DFT, Docking, electrochemical, TGA studies and vibrating sample magnetometer analysis techniques. Limit of detection (LOD) values were calculated as 2 × 10-10 M and 4.17 × 10-8 M for Ni(II) metal ion in emission and absorption based techniques respectively and 2.8 × 10-9 M and 4.5 × 10-6 M for Co(II). EDTA based Reversible binding behaviour suggested its potential for constructing molecular logic gates. Catalytic studies of metal complexes of TBZT with these metals demonstrated TBZT-Co(II) superior activity in reducing nitro-phenol, rhodamine B and methyl red. Real sample analysis validated its capability for the environmental monitoring of these metal ions. This emphasized its potential application in metal ion detection and catalysis.

Advances in Coordination Chemistry of Schiff Base Complexes: A Journey from Nanoarchitectonic Design to Biomedical Applications

Since the discovery of Schiff bases over one and a half centuries ago, there has been tremendous research activity in the design of various Schiff bases and examination of their diverse structures and versatile applications. This family of compounds has continued to captivate many research groups due to the simplicity of their synthesis through the condensation of amines with carbonyl compounds. While conventional synthesis has been the most widely used, green synthetic methodologies have been also explored for this reaction, including sonication, microwave-assisted, natural acid-catalyzed and mechanochemical syntheses as well as utilizing ionic liquid solvents or deep eutectic solvents. Schiff bases have been utilized as excellent ligands for coordination to transition metals and late transition metals (lanthanides and actinides). These Schiff base compounds can be mono-, di-, or polydentate ligands. The aim of this review is to examine the biological applications of Schiff base complexes over the past decade with particular focus on their antimicrobial, antiviral, anticancer, antidiabetic, and anti-inflammatory activity. Schiff base complexes have been found effective in combating bacterial and fungal infections with numerous examples in the literature. The review addressed this area by focusing on the very recent examples while using tables to summarize the vast breadth of research according to the metallic moieties. Viruses have continued to be a target of many researchers in light of their continuous mutations and impact on human health, and therefore some examples of Schiff base complexes with antiviral activity are described. Cancer continues to be among the leading causes of death worldwide. In this article, the use of Schiff base complexes for, and the mechanisms associated with, their anticancer activity are highlighted. The production of reactive oxygen species (ROS) or intercalation with DNA base pairs leading to cell cycle arrest were the main mechanisms described. While there have been some efforts made to use Schiff base complexes as antidiabetic or anti-inflammatory agents, there are limited examples when compared with antimicrobial and anticancer studies. The conclusion of this review highlights the emerging areas of research and future perspectives with an emphasis on the potential uses of Schiff bases in the treatment of infectious and noninfectious diseases.

New Pd(II) complexes of the bisthiocarbohydrazones derived from isatin and disubstituted salicylaldehydes: Synthesis, characterization, crystal structures and inhibitory properties against some metabolic enzymes

Pd(II) complexes (Pd1, Pd2, and Pd3) were synthesized for the first time using asymmetric isatin bisthiocarbohydrazone ligands and PdCl₂(PPh₃)₂. All complexes were characterized by a range of spectroscopic and analytical techniques. The molecular structures of Pd1 and Pd3 have been determined by single-crystal X-ray diffraction analysis. The complexes are diamagnetic and exhibit square planar geometry. The asymmetric isatin bisthiocarbohydrazone ligands coordinate to Pd(II) ion in a tridentate manner, through the phenolic oxygen, imine nitrogen and thiol sulfur, forming five- and six-membered chelate rings within their structures. The fourth coordination site in these complexes is occupied by PPh₃ (triphenylphosphine). The free ligands and their Pd(II) complexes were evaluated for their carbonic anhydrase I, II (hCAs) and acetylcholinesterase (AChE) inhibitor activities. They showed a highly potent inhibition effect on AChE and hCAs. K_i values are in the range of 9 ± 0.6 - 30 ± 5.4 nM for AChE, 7 ± 0.5 - 16 ± 2.2 nM for hCA I and 3 ± 0.3-24 ± 1.9 nM for hCA II isoenzyme. The results clearly demonstrated that the ligands and their Pd(II) complexes effectively inhibited the used enzymes.

Anticancer activity and cell death mechanism of Pt(II) complexes: Their in vitro bio-transformation to Pt(II)-DNA adduct formation and BSA binding study by spectroscopic method

Pt(II) complex cis-[Pt(PEA)(OH₂)₂] X₂, C-2 (where, PEA = 2-Pyridylethylamine and X  = ClO₄^- or NO₃^-) was synthesized by hydrolysis of cis-[Pt(PEA)Cl₂] C-1. Glutathione (GSH) and DL-penicilamine (DL-pen) substituted complexes cis-[Pt(PEA)(GSH)],C-3 and cis-[Pt(PEA)DL-pen)]X C-4 were synthesized and characterized by spectroscopic methods. Kinetic studies were traced on complex C-2 with the thiols, GSH and DL-pen. Pt(II)-Sulfur adduct formation mechanisms of the substituted products C-3 and C-4 were established from the kinetic investigation. At pH 4.0, C-2 - thiols interactions follow two consecutive steps: the first step is dependent, and the second is independent of [thiol]. The association equilibrium constant (K_E), substitution rate constants for both steps (k₁ & k₂), and activation parameters (ΔH^‡ and ΔS^‡) have been assessed to propose the mechanism. Agarose gel electrophoresis mobilization pattern of DNA with complexes was performed to visualize the interaction nature. CT-DNA and BSA binding activities of the complexes have been executed by electronic, fluorescence spectroscopy, and viscometric titration methods. Evaluation of thermodynamic parameters (ΔH⁰, ΔS⁰, and ΔG⁰) from BSA binding constants was executed to propose the driving forces of interaction between these species. A molecular docking study was performed to evaluate the binding mode of complexes with BDNA strands. Anticancer activity of the complexes C-1 to C-4 was explored on both A549 and HEp-2 cell lines, compared with approved anticancer drugs cisplatin, carboplatin, and oxaliplatin. All these complexes were tested by NBT assay on normal cell line skeletal muscle cells (L6 myotubes) to observe the adverse effects compared to recognized anticancer medications. The ultimate aim is to explore the role of anticancer agents on cell death mechanism, which has been performed by flow-cytometer on HEp-2 cell lines.

Schiff bases and their metal complexes with biologically compatible metal ions; biological importance, recent trends and future hopes

Schiff bases are in the field of medicinal and material chemistry for a long time. There are several advancements from time to time towards facile synthesis and potential applications. As medicines they have been applied as organic molecules as well as their metal complexes. The activities of metal complexes have been found to increase due to increase lipophilicity in comparison to the corresponding free ligand. Besides simple coordination compounds they have been applied as ionic liquid (IL)- supported and IL-tagged species with far enhanced efficiency. Among metal complexes recent advancement deals with photodynamic therapy to treat a number of tumors with fewer side effects. Schiff bases are efficient ligands and their complexes with almost all metal ions are reported. This mini-review article deals with complexes of Schiff bases with biologically compatible metal ions, Co(II), Cu(II), Zn(II), Pd(II), Ag(I), Pt(II) and their potential uses to combat cancerous cells. Strong hopes are associated with photodynamic therapy and IL-tagged and IL-supported Schiff bases and their complexes.

A review: Pharmacological aspects of metal based 1,2,4-triazole derived Schiff bases

Clinical reports have highlighted the radical increase of antibiotic resistance. As a result, multidrug resistance has emerged as a serious threat to human health. Many organic compounds commonly used as drugs in the past, no longer have pure organic mode of action rather need bio-transformation or more activation. Bulk of research has shown that they need trace amount of metal ions incorporated within the chemistry of bioactive molecules for enhancement of their potentiality to fight aggressively against resistance. The deficiency of some metal ions can also be responsible for many diseases like growth retardation, pernicious anemia and heart diseases in infants. To overcome these problems, there is a need to introduce novel strategies which have new mechanism of action along with significant spectrum of biological activity, enhanced safety and efficacy. Bioinorganic compounds have played imperative role in developing the new strategy in the form of "Metal Based Drugs". In current years there have been momentous rise of interest in the application of metal based Schiff base compounds to treat various diseases which are difficult to be treated with conventional methodologies. The unique properties of metal chelates acting as an intermediate between conventional organic and inorganic compounds provided innovative opportunities in the field of pharmaceutical chemistry. In this review, we have exclusively focused on the search of metal based 1,2,4-triazole derived Schiff base compounds (synthesized, reported and reviewed in the past ten years) that possess various biological activities such as antifungal, antibacterial, antioxidant, antidiabetic, anthelmintic, anticancer, antiproliferative, cytotoxic and DNA-intercalation activity.

Synthesis and photophysical study of divalent complexes of chelating Schiff base

Background: Schiff base compounds derivative from1,2,4-triazole, and their transition metal complexes play an essential role in coordination and bioinorganic chemistry due to biological and industrial applications. Objectives: This work aims to prepare and characterize 1,2,4-triazole Schiff base and its complexes with a theoretical study, photophysical properties, and surface morphology for these complexes. Methods: 1,2,4-triazole Schiff base prepared by condensation reaction between 4-Amino-3-mercapto-5-phenyl-4H-1,2,4-triazole and 2-hydroxy-1-naphthaldehyde, then Schiff base reacted with Co2+, Ni2+, and Cu2+ ions, the synthesized 1,2,4-triazole Schiff base, and its complexes were characterized by infrared spectra, magnetic susceptibility, conductivity measurements, photophysical properties, and surface morphology measured by atomic force microscopy. The practical results were reinforced with a theoretical study, using PM3 calculation and HyperChem program, for these Schiff base complexes. Then, the proposed structures of the prepared complexes. Results: 1,2,4-triazole Schiff base act as a chelate ligand. The coordination has occurred through the oxygen of the phenolic group O-H and the nitrogen of the imine group N=C of Schiff base with divalent metal ions. Cobalt complex has a tetrahedral geometry, while the nickel and copper complexes have square planar geometries. The stability of all compounds was studied by calculating the energy gap by diffuse reflectance spectroscopy and theoretical calculations. Copper Schiff base is a more stable complex due to the lower value of the energy gap, and the copper Schiff base complex is more semiconductivity than the other complexes. Surface morphology, properties of chelating Schiff base ligand and its complexes measured by atomic force microscopy, cobalt Schiff base complex is higher roughness. The bond length of (-C=N-), (-C-O-),(M-O), and (M-N) are affected in the coordination with metal ions, the bond length of the square planar geometry more affected than tetrahedral geometry. Conclusions: All compounds were prepared successfully, characterized, and photophysical properties were studied.

Synthesis, characterization, antiproliferative of pyrimidine based ligand and its Ni(II) and Pd(II) complexes and effectiveness of electroporation

In the study, a new Schiff base (ligand) was obtained using 4-aminopyrimidine-2(1H)-one, the starting material, and 2,3,4-trimethoxy benzaldehyde. Ni(II) and Pd(II) complexes were obtained from the reaction of the ligand and NiCl₂·6H₂O, PdCl₂(CH₃CN)₂ (1:1 ratio). These compounds were characterized using the elemental and mass analysis, ¹H, ¹³C-NMR, FT-IR, UV-Vis, magnetic susceptibility, thermal analysis, and the X-ray diffraction analyses. The antiproliferative activities of the synthesized ligand, Ni(II) and Pd(II) complexes were identified on the HepG2 (human liver cancer cells) cell line and their biocompatibility was tested on the L-929 (fibroblast cells) cell line by the MTT analysis method. Furthermore, the effects of electroporation (EP) on the cytotoxic activities of synthesized compounds were investigated in HepG2 cancer cells. According to the MTT findings of the study, the ligand did not exhibit an antiproliferative activity while its Ni(II) and Pd(II) complexes exhibited an antiproliferative activity. Moreover, it was observed that the antiproliferative activity of the Pd(II) complex was stronger than that of the Ni(II) complex. The combined application of EP + compounds is much more effective than the usage of the compounds alone in the treatment of HepG2 cancer cells. The EP increased the cytotoxicity of the Ni(II) and Pd(II) complexes by 1.66, and 2.54 times, respectively. It was concluded that Ni(II) and Pd(II) complexes may contribute as potential anti-cancer agents for the treatment of hepatocellular carcinoma and yield promising results in the case of being used in ECT.Communicated by Ramaswamy H. Sarma.

Seven membered chelate Pt(ii) complexes with 2,3-di(2-pyridyl)quinoxaline ligands: studies of substitution kinetics by sulfur donor nucleophiles, interactions with CT-DNA, BSA and in vitro cytotoxicity activities

Dichloro platinum(ii) complexes coordinated with 2,3-di(2-pyridyl)quinoxaline ligands which form seven-membered chelates namely, bpqPtCl2, dmbpqPtCl2 and bbqPtCl2 (where bpq, dmbpq and bbq are 2,3-di(2-pyridyl)quinoxaline, 6,7-dimethyl-2,3-di(2-pyridyl)quinoxaline and 2,3-bis(2'pyriyl)benzo[g]quinoxaline, respectively) were synthesized, characterised and their respective hydrated product complexes namely, bpqPt(OH2)2 2+, dmbpqPt(OH2)2 2+ and bbqPt(OH2)2 2+ were prepared by chloride metathesis. The substitution kinetics of the aquated cations by thiourea nucleophiles indicated that the two aqua ligands are substituted simultaneously according to the rate law: k obs = k 2[Nu]. This is followed by a forced dechelation of the ligands from the Pt (II) to form Pt(Nu)4 2+ species. The dechelation step is considerably slow to be monitored reliably. The rate of substitution is marginally enhanced by introducing two methyl groups and by extending the π-conjugation on the bpq core ligand. The reactivity order increased as bpqPt(OH2)2 2+ < dmbpqPt(OH2)2 2+ < bbqPt(OH2)2 2+. Reactivity trends were well supported by theoretical computed DFT electronic descriptors. The interactions of the Pt(ii) complexes with CT-DNA and BSA were also examined spectroscopically in tris buffers at pH 7.2. Spectroscopic and viscosity measurements suggested strong associative interactions between the Pt(ii) complexes and CT-DNA, most likely through groove binding. In silico theoretical binding studies showed energetically stable poses through associative non-covalent interactions. In vitro MTT cytotoxicity IC50 values of the Pt(ii) complexes on human liver carcinoma cells (HepG2) cancer cell lines revealed bbqPtCl2 as the least active. The fluorescence staining assays revealed the morphological changes suggested early apoptotic induction as well as non-specific necrosis.

Synthesis, Structural Characterization, Molecular Modeling and DNA Binding Ability of CoII, NiII, CuII, ZnII, PdII and CdII Complexes of Benzocycloheptenone Thiosemicarbazone Ligand

Background & Objective:

Six novel complexes of transition metal namely, [CoLCl2(H2O)2]0.5H2O, [NiLCl2(H2O)2]0.5H2O, [CuLCl2]0.5H2O, [ZnLCl2], [PdLCl2]H2O and [CdLCl2]H2O, where L is benzocycloheptenone thiosemicarbazone ligand, have been obtained. The confirmation of the structures of the obtained metal chelates depends on the different spectral and physicochemical techniques including CHN analysis, infrared spectra, molar conductivity measurement, UV-vis, thermogravimetric analysis and magnetic moment. The infrared spectral results ascertained that the ligand behaved as neutral bidentate connecting the metal centers via N and S atoms of C=N and C=S groups, respectively.

Methods:

The UV-Vis, molar conductivity and magnetic susceptibility results implied that the geometrical structures of the metal chelates are octahedral for Co(II) & Ni(II) complexes, tetrahedral for Zn(II) & Cd(II) complexes and square planar for Cu(II) & Pd(II) complexes which have been confirmed by molecular modeling studies.

Conclusion:

Moreover, the mode of interaction between some chosen metal complexes towards SSDNA has been thoughtful by UV-Vis spectra and viscosity measurements. The value of the intrinsic binding constant (Kb) for the examined compounds has been found to be lower than the binding affinity of the classical intercalator ethedium bromide. Also, the viscosity measurements of the complexes proved that they bind to DNA, most likely, by a non-intercalative mode like H-bonding or electrostatic interactions.

A palladium(II) complex with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol: Synthesis, structural characterization, and in vitro and in silico biological activity studies

The synthesis and characterization of the Pd(II) complex of the formula [Pd(L)₂] 1 with the Schiff base 4-chloro-2-(N-ethyliminomethyl)-phenol (HL) as derived in situ via the condensation reaction of 5-chloro-salicylaldehyde and ethylamine was undertaken. The structure of 1 was verified by single-crystal X-ray crystallography. The ability of 1 to interact with calf-thymus (CT) DNA was studied by UV-vis and viscosity experiments, and its ability to displace ethidium bromide (EB) from the DNA-EB conjugate was revealed by fluorescence spectroscopy. It was found that intercalation is the most possible mode of interaction with CT DNA. Additionally, DNA electrophoretic mobility experiments showed that 1 interacts with the plasmid pBluescript SK(+) (pDNA) as proved by the formation of unusual mobility DNA bands and degradation of relaxed pDNA at concentration of 5 mM. The interaction of 1 with human (HSA) and bovine serum albumin (BSA) was monitored revealing its reversible binding to albumins. The complex showed noteworthy antimicrobial activity against one (Bacillus subtilis) of the five tested bacteria. In order to explain the described in vitro activity of the compound, we adopted molecular docking studies on the crystal structure of HSA, BSA, CT DNA and DNA-gyrase. Furthermore, in silico predictive tools have been employed to study the properties of the complex. The in silico studies are adopted on a multitude of proteins involved in cancer growth, as well as prediction of drug-induced changes of gene expression profile, protein- and mRNA-based prediction results, prediction of sites of metabolism, cytotoxicity for cancer cell lines, etc.

Palladium(II) complexes with salicylaldehyde ligands: Synthesis, characterization, structure, in vitro and in silico study of the interaction with calf-thymus DNA and albumins

The synthesis and characterization of four palladium(II) complexes with substituted salicylaldehydes (X-saloH) having the general formula [Pd(X-salo)₂] was undertaken. The complexes are formulated as [Pd(3-OCH₃-salo)₂] 1, [Pd(5-NO₂-salo)₂] 2, [Pd(5-Cl-salo)₂] 3, and [Pd(5-Br-salo)₂] 4. The structure of complex 1 was verified by single-crystal X-ray crystallography. Spectroscopic (UV-vis), and physicochemical (viscosity measurements) techniques were employed in order to study the binding of the complexes with calf-thymus (CT) DNA, while ethidium bromide (EB) displacement studies, performed by fluorescence emission spectroscopy, revealed the ability of the complexes to displace the DNA-bound EB. Intercalation is the most possible mode of interaction of the complexes with CT DNA. The interaction of the complexes with bovine (BSA) and human (HSA) serum albumin proteins was studied by fluorescence emission spectroscopy and the relatively high binding constants revealed the reversible binding of the complexes to the albumins. Molecular docking simulations on the crystal structure of HSA, BSA and CT DNA were employed in order to study in silico the ability of the studied complexes 1-4 to bind to these target macromolecules.

Schiff Base Metal Complexes as Anticancer Agents

Cutting-edge practices in bioinorganic chemistry are pivotal for enhancing the layout of compounds to lessen poisonous facet effect and recognize their mechanism of action. A powerful anticancer agent should own inherent, inhibitory property and also delivery, dosage and residence time in vivo. Organic function and conformation of mutated gene may be altered by way of binding of metal ions. Upswing of activities counting on the structural data, intending in enhancing and growing different forms of metal based compounds, continuous seek of extra metal based compounds have been synthesized via revamping the prevailing chemical shape via ligand substitution. The prevailing paper addresses the trendy development in the design of novel antitumor agents primarily based on transition metal complex via highlighting the near dating among their structural alternatives and cytotoxic ability.

An experimental and theoretical study on the interaction of DNA and BSA with novel Ni2+, Cu2+ and VO2+ complexes derived from vanillin bidentate Schiff base ligand

In this investigation, the structure of bidentate N,N-Schiff base ligand of vanillin, (E)-4-(((2-amino-5-nitrophenyl)imino)methyl)-2-methoxyphenol (HL) was determined by single crystal X-ray diffraction. The interaction of new [CuL₂], [NiL₂] and [VOL₂] complexes with DNA and BSA was explored through UV-Vis and fluorescence spectroscopy. The electronic spectra changes displayed an isosbestic point for the complexes upon titration with DNA. The K_b values for the complexes [CuL₂], [NiL₂] and [VOL₂] were 2.4×10⁵, 1.9×10⁵ and 4.2×10⁴, respectively. [CuL₂] complex was bound more toughly than [NiL₂] and [VOL₂] complexes. These complexes had a significant interaction with Bovine Serum Albumin (BSA) and the results demonstrated that the quenching mechanism was a static procedure. Also, the complexes interacted with BSA by more than one binding site (n>1). Finally, the theoretical studies were performed using the docking method to calculate the binding constants and recognize the binding site of the DNA and BSA with the complexes. The ligand and complexes including Ni²⁺, Cu²⁺ and VO²⁺ ions were colonized by fungal growth.