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(E)-N,N-Dimethyl-2-((E-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide (DMPTHP) and their Zn(II) and Cd(II) complexes have been synthesized and characterized. Different tools of analysis such as elemental analyses, IR, mass spectra, and 1H-NMR measurements were used to elucidate the structure of the synthesized compounds. According to these spectral results, the DMPTHP ligand behaved as a mononegatively charged tridentate anion. Modeling and docking studies were investigated and discussed. Novel Schiff base (DMPTHP) ligand protonation constants and their formation constants with Cd(II) and Zn(II) ions were measured in 50% DMSO solution at 15°C, 25°C, and 35°C at I = 0.1 mol·dm−3 NaNO3. The solution speciation of different species was measured in accordance with pH. Calculation and discussion of the thermodynamic parameters were achieved. Both log K1 and –ΔH1, for M(II)-thiosemicarbazone complexes were found to be somewhat larger than log K2 and –ΔH2, demonstrating a shift in the dentate character of DMPTHP from tridentate in 1 : 1 chelates to bidentate in 1 : 2; M : L chelates and steric hindrance were generated by addition of the 2nd molecule. The compounds prepared have significant activity as antioxidants, similar to ascorbic acid. It is hoped that the results will be beneficial to antimicrobial agent chemistry. The formed compounds acted as a potent antibacterial agent. Molecular docking studies were investigated and have proved that DMPTHP as antibacterial agents act on highly resistant strains of E. coli and also as an anticancer agent. [ABSTRACT FROM AUTHOR]

Schiff bases (SBs) are aldehyde- or ketone-like compounds in which the carbonyl group is replaced by an imine or azomethine. In spite of the large interest always shown in the coordination properties of Schiff base ligands and the attention paid in recent years to the possible variable biological activities of their metal complexes, studies dealing with protonation and formation equilibria of Schiff bases and their complexes are still very rare. Thus, the importance of the determination of the equilibrium constants of Schiff bases and their complex formation equilibria is of paramount importance to understand the complicated biological reactions like transamination, racemization and decarboxylation. The 33 ligands considered herein include salicylaldehyde/substituted salicylaldehyde SBs and salicylaldehyde/substituted salicylaldehyde amino acid SBs. This article is focused on protonation and complex-formation equilibria of salicylaldehyde or substituted salicylaldehyde SBs and salicylaldehyde amino acid SBs in aqueous and nonaqueous solutions, taking into account also the structure-activity correlation of SBs and their metal(II) complexes based on their stability constants. Activity of SBs enhances upon complexation and the order of activity is nearly in accord with the order of the formation constants of metal ions. The few enthalpy and entropy changes available for such protonation and complex-formation reactions are reported and discussed. [ABSTRACT FROM AUTHOR]

Abstract: Schiff base ligand, 1,4-bis[(2-hydroxybenzaldehyde)propyl]piperazine (BHPP), and its Cu(II), Ni(II) and Co(II) metal complexes were synthesized and characterized by elemental analysis, magnetic susceptibility, molar conductance and spectral (IR and UV–vis) studies. The ground state of BHPP ligand was investigated using the BUILDER module of MOE. Metal complexes are formed in the 1:1 (M:L) ratio as found from the elemental analysis and found to have the general formula [ML]·nH2O, where M=Co(II), Ni(II) and Cu(II), L=BHPP. In all the studied complexes, the (BHPP) ligand behaves as a hexadentate divalent anion with coordination involving the two azomethine nitrogen’s, the two nitrogen atoms of piperazine ring and the two deprotonated phenolic OH-groups. The magnetic and spectral data indicates octahedral geometry of metal(II) complexes. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria and fungi. They were found to be more active against Gram-positive than Gram-negative bacteria. Protonation constants of (BHPP) ligand and stability constants of its Cu2+, Co2+ and Ni2+ complexes were determined by potentiometric titration method in 50% DMSO–water solution at ionic strength of 0.1M sodium nitrate. It has been observed that the protonated Schiff base ligand (BHPP) have four protonation constants. The divalent metal ions Cu2+, Ni2+ and Co2+ form 1:1 complexes. [Copyright &y& Elsevier]

Abstract: Schiff base namely 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS)(4-bromo-2-(thiophen-2-yl-imino)methylphenol) and its metal complexes have been synthesized and characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, ESR and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:2 [M:L] ratio of the formula [ML2], where M represents Ni(II), Zn(II) and Cu(II) ions, while L represents the deprotonated Schiff base. IR spectra show that ATS is coordinated to the metal ions in a bidentate manner through azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria. A cytotoxicity of the compounds against colon (HCT116) and larynx (HEP2) cancer cells have been studied. Protonation constants of (ATS) ligand and stability constants of its Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ complexes were determined by potentiometric titration method in 50% (v/v) DMSO–water solution at ionic strength of 0.1M NaNO3. [Copyright &y& Elsevier]

Abstract Schiff bases complexes of Co(II) and Ni(II) ions with diethyl 3,3'-(ethane-1,2-diylbis (azaneylylidene)) (3E, 3′ E)-dibutyrate (H 2 L1) and (3E, 3′ E)-3,3'-(ethane-1,2-diylbis (azanylylidene))bis (N -(pyridin-2-yl)butanamide) (H 2 L2) have been synthesized, characterized and analytically formulated as [Co 2 (L1)Cl 2 ·2H 2 O]·H 2 O (1) , [Ni 2 (L1)Cl 2 ·6H 2 O]·2H 2 O (2) , [Co 2 (H 2 L2)Cl 4 ·2H 2 O]·H 2 O (3) and [Ni(H 2 L2)Cl 2 ]·H 2 O (4). The IR spectral data revealed that H 2 L1 ligand behaves as a N 2 O 2 binegative tetradentate in (1) and (2) through the oxygen of both enolized carbonyl (C O) groups and the nitrogen of two newly formed (C N)∗ groups. While H 2 L2 acts as neutral NNOONN hexadentate in (3) and as a neutral NNOO tetradentate in (4). The spectral and magnetic studies suggests a tetrahedral coordination geometry for complex (1) and octahedral geometry for other complexes. In addition, thermal degradation curves have been discussed for complexes in order to estimate their kinetic and thermodynamic parameters by two comparable methods. Various descriptors have been estimated using DFT calculations. Moreover, the anti-microbial activities and MTT cytotoxicity assay of the compounds have been examined. Graphical abstract Image 1 Highlights • Co(II) and Ni(II) complexes of new Schiff base ligands have been isolated. • 1HNMR, 13CNMR and mass spectra of both Schiff base ligands were determined. • Thermal behavior were studied for the metal complexes using TGA technique. • DFT studies were utilized to confirm the geometry. • Antimicrobial activity and MTT assay were tested for the investigated compounds. [ABSTRACT FROM AUTHOR]

Metallic antitumor drugs with heterocyclic ligands, such as novel AMI (amino methyl imidazole) complexes [Pd(AMI)Cl2](1), [Cu(AMI)L1](2), and [Cu(AMI)L2·2H2O](3) where L1 = oxalate and L2 = malonate, were synthesized and characterized. Assessments included elemental analyses, mass spectrometry, Fourier transform-infrared spectroscopy, ultraviolet–visible spectroscopy, and thermal analysis. The cytotoxicity of AMI complexes compared to cisplatin was assessed using MTT (3-[4,5-dimethylthiazol-2-yl] 2,5diphenyl tetrazolium bromide) assay with breast (MCF-7) and cervical (HeLa) cancer cell lines. After treating these cells with the AMI complexes' IC50 values for 48 h, malondialdehyde levels and catalase activity were used to assess oxidative stress, antioxidant activity was evaluated with DPPH radical scavenging method, comet assays assessed DNA damage, and DNA fragmentation was evaluated using the gel electrophoresis. In vitro, antimicrobial activity was assessed using a disc diffusion method. The anticancer activity results showed that IC50 (half-maximal inhibitory concentration) values of complex one, two, and three against MCF-7 and HeLa cancer cells are 0.156 ± 0.0006, 0.125 ± 0.001, 0.277 ± 0.002 μM respectively for MCF-7 cells and 0.222 ± 0.0005, 0.126 ± 0.0009, 0.152 ± 0.001 μM respectively for HeLa cells. Complex two demonstrated strong anticancer activity against MCF-7 and Hela cells. The study of oxidative stress parameters revealed that Malondialdehyde levels increased in cancer cell lines treated with complexes compared to untreated cells. Catalase activity decreased in cells treated with palladium chelate. The DPPH radical scavenging assay results identified that complex one was a more potent antioxidant in MCF-7 and Hela cells than other complexes with SC50 values of 227.5 ± 0.28 and 361 ± 1.2 μL/mL, respectively. The comet assay results showed that complex two caused significant DNA damage in MCF-7 and HeLa cancer cells treated. Antimicrobial assays identified complex three as the most effective. Copper complexes give better antifungal activity against A. flavus than the palladium complex. We conclude that complex two is the most active in both cell types and might be assessed as a clinically useful drug for breast cancer treatment. The significance of the current study is the synthesis of antitumor drugs containing heterocyclic ligands, such as novel AMI complexes, and the study of their biological activities. [ABSTRACT FROM AUTHOR]

Review: 120 refs. [ABSTRACT FROM AUTHOR]

Ternary complexes of copper(II) with 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS) and some amino acids have been isolated and characterized by elemental analyses, IR, magnetic moment, molar conductance, UV–vis, mass spectra, and ESR. The proposed general formulas of the prepared complexes are [Cu(ATS)(AA)]·nH2O (where AA?=?glycine, alanine, and valine). The low molar conductance values suggest the non-electrolytic nature of the complexes. IR spectra show that ATS is coordinated to copper in a bidentate manner through azomethine-N and phenolic-OH. The amino acids also are monobasic bidentate ligands via amino and ionized carboxylate groups. The magnetic and spectral data indicate the square-planar geometry of Cu(II) complexes. The geometry of the Cu(II) complexes has been fully optimized using parameterized PM3 semiempirical method. The Cu–N bond length is longer than that of Cu–O in the isolated complexes. Also, information is obtained from calculations of molecular parameters for all complexes including net dipole moment of the metal complexes, values of binding energy, and lipophilicity value (logP). The antimicrobial activity studies indicate significant inhibitory activity of complex3against the selected types of bacteria. The mixed ligand complexes have also been studied in solution state. Protonation constants of ATS and amino acids were determined by potentiometric titration in 50% (v/v) DMSO–water solution at ionic strength of 0.1?M NaCl. ATS has two protonation constants. The binary and ternary complexes of copper(II) involving ATS and some selected amino acids (glycine, alanine, and valine) were examined. Copper(II) forms [Cu(ATS)], [Cu(ATS)2], [Cu(AA)], [Cu(AA)2], and [Cu(ATS)(AA)] complexes. The ternary complexes are formed in a simultaneous mechanism. The present paper reports on the synthesis, characterization, and the electronic absorption spectra of Cu(II) ternary complexes involving ATS-Schiff base, and some selected amino acids. The antibacterial, antifungal, and antitumor activities were investigated. The geometry of the studied Cu(II) complexes has been fully optimized using parameterized PM3 semiempirical method. Protonation and complex formation equilibria were investigated. [ABSTRACT FROM PUBLISHER]