Synthesis, spectroscopic, and antimicrobial studies on bivalent zinc and mercury complexes of 2-formylpyridine thiosemicarbazone

Efficient Synthesis, Spectroscopic Characterization, and Nonlinear Optical Properties of Novel Salicylaldehyde-Based Thiosemicarbazones: Experimental and Theoretical Studies

Currently, we reported the synthesis of six novel salicylaldehyde-based thiosemicarbazones (BHCT1-HBCT6) via condensation of salicylaldehyde with respective thiosemicarbazide. Through various spectroscopic methods, UV-visible and NMR, the chemical structures of BHCT1-HBCT6 compounds were determined. Along with synthesis, a computational study was also performed at the M06/6-31G(d,p) functional. Various analyses such as natural bond orbital (NBO) analysis, natural population analysis, frontier molecular orbital (FMO) analysis, and molecular electrostatic potential surfaces were carried out to understand the nonlinear optical (NLO) characteristics of the synthesized compounds. Additionally, a comparative study was carried out between DFT and experimental results (UV-vis study), and a good agreement was observed in the results. The energy gap calculated through FMOs was found to be in decreasing order as 4.505 (FHCT2) > 4.499 (HBCT6) > 4.497 (BHCT1) = 4.497(HMCT5) > 4.386 (CHCT3) > 4.241(AHCT4) in eV. The global reactivity parameters (GRPs) were attained through E _HOMO and E _LUMO, which described the stability and hardness of novel compounds. The NBO approach confirmed the charge delocalization and stability of the molecules. Among all the investigated compounds, a larger value (557.085 a.u.) of first hyperpolarizability (β_tot) was possessed by CHCT3. The NLO response (β_tot) of BHCT1-HBCT6 was found to be 9.145, 9.33, 13.33, 5.43, 5.68, and 10.13 a.u. times larger than that of the standard para-nitroaniline molecule. These findings ascertained the potential of entitled ligands as best NLO materials for a variety of applications in modern technology.

Exploring Novel Pyridine Carboxamide Derivatives as Urease Inhibitors: Synthesis, Molecular Docking, Kinetic Studies and ADME Profile

The rapid development of resistance by ureolytic bacteria which are involved in various life-threatening conditions such as gastric and duodenal cancer has induced the need to develop a new line of therapy which has anti-urease activity. A series of pyridine carboxamide and carbothioamide derivatives which also have some novel structures were synthesized via condensation reaction and investigated against urease for their inhibitory action. Among the series, 5-chloropyridine-2 yl-methylene hydrazine carbothioamide (Rx-6) and pyridine 2-yl-methylene hydrazine carboxamide (Rx-7) IC50 = 1.07 ± 0.043 µM, 2.18 ± 0.058 µM both possessed significant activity. Furthermore, molecular docking and kinetic studies were performed for the most potent inhibitors to demonstrate the binding mode of the active pyridine carbothioamide with the enzyme urease and its mode of interaction. The ADME profile also showed that all the synthesized molecules present oral bioavailability and high GI absorption.

Arene-Ruthenium(II) Complexes with Carbothiamidopyrazoles as a Potential Alternative for Antibiotic Resistance in Human

To meet the demand for alternatives to commonly used antibiotics, this paper evaluates the antimicrobial potential of arene-ruthenium(II) complexes and their salts, which may be of value in antibacterial treatment. Their antimicrobial activity (MIC, MBC/MFC) was examined in vitro against Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris and Candida albicans and compared with classic antibiotics used as therapeutics. Selected arene-ruthenium(II) complexes were found to have synergistic effects with oxacillin and vancomycin against staphylococci. Their bactericidal effect was found to be associated with cell lysis and the ability to cut microbial DNA. To confirm the safety of the tested arene-ruthenium(II) complexes in vivo, their cytotoxicity was also investigated against normal human foreskin fibroblasts (HFF-1). In addition, the antioxidant and thus pro-health potential of the compounds, i.e., their nonenzymatic antioxidant capacity (NEAC), was determined by two different methods: ferric-TPTZ complex and DPPH assay.

Antifungal activity of thiosemicarbazones, bis(thiosemicarbazones), and their metal complexes

Fungi are ubiquitous in nature, and typically cause little or no environmental or pathogenic damage to their plant, animal, and human hosts. However, a small but growing number of pathogenic fungi are spreading world-wide at an alarming rate threatening global ecosystem health and proliferation. Many of these emerging pathogens have developed multi-drug resistance to front line therapeutics increasing the urgency for the development of new antifungal agents. This review examines the development of thiosemicarbazones, bis(thiosemicarbazones), and their metal complexes as potential antifungal agents against more than 65 different fungal strains. The fungistatic activity of the compounds are quantified based on the zone of inhibition, minimum inhibitory concentration, or growth inhibition percentage. In this review, reported activities were standardized based on molar concentrations to simplify comparisons between different compounds. Of all the fungal strains reported in the review, A. niger in particular was very resistant towards a majority of tested compounds. Our analysis of the data shows that metal complexes are typically more active than non-coordinated ligands with copper(II) and zinc(II) complexes generally displaying the highest activity.

Computational Studies of 4-Formylpyridinethiosemicarbazone and Structural and Biological Studies of Its Ni(II) and Cu(II) Complexes

To understand the stability, chelation behaviour, and biological activity of 4-Formylpyridinethiosemicarbazone (H4FPT), it is important to recognize its interactive geometry. Hence, computational studies on geometrically optimized structures of thione and thiol forms of H4FPT were performed. Binary metal complexes of the ligand, H4FPT (L) with the Ni(II) and Cu(II) metal ions (M), were synthesized and characterized by various spectroanalytical techniques as elemental analysis, molar conductance, magnetic susceptibility measurements, LC-MS, TGA, IR, UV-Visible, ESR, and powder XRD. Elemental analysis, LC-MS, and TGA studies indicate 1:2 (ML2) composition for mononuclear Ni(II) complex and 1:1 (ML) composition for dinuclear Cu(II) complex. Electronic absorption titrations, fluorescence quenching studies, and viscosity measurements suggest intercalative mode of binding of the complexes with calf thymus DNA (CT-DNA). These complexes also promote hydrolytic cleavage of plasmid pBR322. The ligand (H4FPT) and its complexes showed moderate-to-good activity against Gram-positive and Gram-negative bacterial strains. The DPPH radical scavenging studies showed antioxidant nature of both complexes.

Calcium release induced by 2-pyridinecarboxaldehyde thiosemicarbazone and its copper complex contributes to tumor cell death

Thiosemicarbazones display significant antitumor activity and their copper complexes also exhibit enhanced biological activities in most situations, but the underlying mechanism is poorly understood. Therefore, investigation of the mechanism involved in the change upon chelation is required to extend our understanding of the effects of thiosemicarbazones. In the present study, the inhibitory effect of 2-pyridinecarboxaldehyde thiosemicarbazone (PCT) and its copper complex (PCT-Cu) on cell proliferation was investigated. The copper chelate exhibited a 3- to 10-fold increase in antitumor activity (with an IC50 <5 µM). The results showed that both PCT and PCT-Cu induced reactive oxygen species (ROS) generation in vitro and in vivo, caused cellular DNA fragmentation, depolarization of the mitochondrial membrane and cell cycle arrest. Western blotting showed that both PCT and PCT-Cu induced apoptosis. Upregulation of GRP78 in HepG2 cells following treatment with the agents indicated that endoplasmic reticulum (ER) stress occurred. Furthermore calcium release was revealed in this study, suggesting that PCT and PCT-Cu disturbed calcium homeostasis. It was noted that PCT-Cu sensitized thapsigargin‑stimulated calcium release from the ER, which was correlated with the ROS level they induced, implying that the antitumor activity of PCT and PCT-Cu partly stemmed from calcium mobilization, a situation that was reported in few studies. Our findings may significantly contribute to the understanding of the anti‑proliferative effect of the derivatives of thiosemicarbazones along with their antitumor mechanism.

Antimicrobial and toxicological evaluations of binuclear mercury(ii)bis(alkynyl) complexes containing oligothiophenes and bithiazoles

We investigated the antimicrobial activity of bis-(alkynyl)mercury(ii) complexes with oligothiophene and bithiazole linking units against MRSA and C. albicans, and their cytotoxicity was tested on NIH 3T3 cells.

Sol-gel encapsulation of binary Zn(II) compounds in silica nanoparticles. Structure-activity correlations in hybrid materials targeting Zn(II) antibacterial use

In the emerging issue of enhanced multi-resistant properties in infectious pathogens, new nanomaterials with optimally efficient antibacterial activity and lower toxicity than other species attract considerable research interest. In an effort to develop such efficient antibacterials, we a) synthesized acid-catalyzed silica-gel matrices, b) evaluated the suitability of these matrices as potential carrier materials for controlled release of ZnSO4 and a new Zn(II) binary complex with a suitably designed well-defined Schiff base, and c) investigated structural and textural properties of the nanomaterials. Physicochemical characterization of the (empty-loaded) silica-nanoparticles led to an optimized material configuration linked to the delivery of the encapsulated antibacterial zinc load. Entrapment and drug release studies showed the competence of hybrid nanoparticles with respect to the a) zinc loading capacity, b) congruence with zinc physicochemical attributes, and c) release profile of their zinc load. The material antimicrobial properties were demonstrated against Gram-positive (Staphylococcus aureus, Bacillus subtilis, Bacillus cereus) and negative (Escherichia coli, Pseudomonas aeruginosa, Xanthomonas campestris) bacteria using modified agar diffusion methods. ZnSO4 showed less extensive antimicrobial behavior compared to Zn(II)-Schiff, implying that the Zn(II)-bound ligand enhances zinc antimicrobial properties. All zinc-loaded nanoparticles were less antimicrobially active than zinc compounds alone, as encapsulation controls their release, thereby attenuating their antimicrobial activity. To this end, as the amount of loaded zinc increases, the antimicrobial behavior of the nano-agent improves. Collectively, for the first time, sol-gel zinc-loaded silica-nanoparticles were shown to exhibit well-defined antimicrobial activity, justifying due attention to further development of antibacterial nanotechnology.

A structural and biological study on the new 3,5-diacetyl-1,2,4-triazol bis(p-chlorophenylthiosemicarbazone) ligand and its bimetallic complexes

Preparation and characterization of the new ligand 3,5-diacetyl-1,2,4-triazol bis(⁴N-p-chlorophenylthiosemicarbazone), H₅L¹, and its bimetallic complexes [Pd(μ-H₃L¹)]₂ and [Pt(μ-H₃L¹)]₂, are described.

Synthesis, Molecular Modeling, and Biological Activity of Zinc(II) Salts with 1,4-Bis(benzimidazol-2-yl)benzene

Zinc(II) halides and perchlorate react with 1,4-bis(benzimidazol-2-yl)benzene (L) in 1 : 2 molar ratio in n-butanol/2-methoxy ethanol (10 mL) at refluxing temperature to produce white/pale yellow-colored complexes of the formulae [ZnCl2L]H2O, [ZnBr2L]3H2O, and [Zn(OClO3)2L]HOCH2CH2CH2CH3. Zinc(II) iodide also reacts with L in 1 : 2 molar ratio in n-butanol (HOCH2CH2CH2CH3) to yield white-colored complex of the formula [ZnL2(OCH2CH2CH2CH3)2]. The complexes were characterized by elemental analysis, molar conductance measurements, thermal analysis, and IR,1H-,13C-NMR spectral studies. The complexes showed significant anthelmintic activity. The minimum energy configuration has been obtained for the zinc complexes using molecular modeling Pro Plus; a tool developed by ChemSW, inc, USA.

catena-Poly[[[aqua-manganese(III)]-μ-(E)-5-bromo-N-[2-(5-bromo-2-oxidobenzyl-idene-amino)-4-nitro-phen-yl]-2-oxidobenzamidato] N,N-dimethyl-fomamide monosolvate]

The asymmetric unit of the title complex, {[Mn(C(20)H(10)Br(2)N(3)O(5))(H(2)O)]·(CH(3))(2)NCHO}(n), consists of one Mn(III) ion, one (E)-5-bromo-N-[2-(5-bromo-2-oxidobenzyl-idene-amino)-4-nitro-phen-yl]-2-oxidobenzamidate ligand (Schiff base), one water mol-ecule and an N,N-dimethyl-formamide mol-ecule. The coordination geometry around the Mn(III) ion is a distorted octa-hedron, being surrounded by two O and two N atoms from the Schiff base, which are positioned in the equatorial plane. The water mol-ecule and the O atom of the carbonyl group from the adjacent Mn(III) complex are situated at the axial positions, leading to a polymeric chain along the c axis. In the crystal, the complex and N,N-dimethyl-formamide mol-ecules are connected via O-H⋯O, C-H⋯O and C-H⋯Br hydrogen bonds, forming a three-dimensional network.

Synthesis, Spectroscopic, Anticancer, and Antimicrobial Properties of Some Metal(II) Complexes of (Substituted) Nitrophenol Schiff Base

The Schiff base, 2-[(2,3-dihydro-1H-inden-4-ylimino)methyl]-5-nitrophenol coordinates to Mn(II), Cu(II), Zn(II), and Pd(II) ions through the phenolic O and imine N atoms. The complexes are characterized by physicochemical and spectroscopic methods. The metal complexes formed as [ML2]xH2O with exception of the Cu(II) complex which is anhydrous. Spectroscopic data corroborate the adoption of a four-coordinate, tetrahedral geometry for the Mn(II), and Zn(II) complexes, and a four-coordinate, square planar geometry for the Cu(II) and Pd(II) complexes. None is an electrolyte in DMSO. The in vitro anticancer activities of the metal free ligand, Cu(II), Zn(II), and Pd(II) complexes against MCF-7 (human breast adenocarcinoma) and HT-29 (colon carcinoma) cells reveal that the Pd(II) complex has the best cytotoxic activity against MCF-7 cells with an IC50 of 5.94 μM, which is within the same order of activity as cisplatin. Furthermore, the ligand and the Zn(II) complex exhibit broad-spectrum activity against two gram-positive bacteria, three gram-negative bacteria, and a fungus with inhibitory zones range of 10.0–20.0 and 10.0–17.0 mm, respectively.