Synthesis, characterization, optical properties, biological activity and theoretical studies of a 4 nitrobenzylidene) amino) phenyl)imino)methyl)naphthalen-2-ol -based fluorescent Schiff base

A new Schiff base, 1-(E)-(4-((E) 4nitrobenzylidene) amino) phenyl)imino) methyl)naphthalen-2-ol (4NMN), was prepared from the reaction of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde and 4-nitrobenzaldehyde and characterized with spectroscopic analysis. UV-VIS and NMR. Frontier molecular orbitals, molecular electrostatic potential, and chemical reactivity descriptors of the synthesized compound were studied using molecular modeling methods. The antibacterial and antifungal activities of the Schiff base were studied for its minimum inhibitory concentration. The compound showed a higher effect on yeast than against bacteria. Density functional theory (DFT) calculations were performed to study the mechanism of reaction for the synthesis of 4NMN, and the results were consistent with the experimental findings. 4NMN exhibited moderate antibacterial and antifungal activities and demonstrated higher inhibition potential against different resistant strains compared to the reference drug gentamycin. The absorption and fluorescence spectra of 4NMN were measured in different solvents, and the effect of relative polarity and acidity on the medium was observed. An inner filter effect was observed at high concentrations, and the compound showed considerable fluorescence enhancement with increasing medium viscosity and fluorescence quenching by the addition of traces of Cr1+ and Cu2+. Additionally, molecular docking studies were conducted to investigate the efficiency of antibacterial and antifungal targets.

Anticancer, antioxidant, and antimicrobial studies and molecular docking of a new hexanuclear Zn(II) complex, together with its X-ray crystal analysis

A new hexanuclear Zn(II) complex with the ligand 2,2'-(piperazine-1,4-diyl)bis(ethan-1-amine), [L3Zn6(OH)6][ClO4]6·3MeOH·7H2O, was synthesized. The crystal structure of this complex showed that each Zn atom is in a distorted tetrahedral coordination environment, surrounded by two nitrogen atoms from each ligand and two hydroxide groups, each of which bridges to another Zn atom. The anticancer activities of the ligand and its metal complex against the breast cancer cell line (MCF-7) indicated that the zinc complex had a greater anticancer activity. The free ligand and its metal complex were evaluated for antioxidant activity using the DPPH scavenging method. In addition, the antibacterial activities of both compounds were screened against Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The interaction of these compounds with DNA and AChE was also investigated using molecular docking.

Triazole based Schiff bases and their Oxovanadium(IV) complexes: Synthesis, characterization, antibacterial assay, and computational assessments

The synthesis and characterization of two new Schiff base ligands containing 1,2,4-triazole moieties and their oxovanadium(IV) complexes have been reported. The ligands and their complexes were studied by ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), proton nuclear magnetic resonance (¹H NMR), electron paramagnetic resonance (EPR), X-ray diffraction (XRD), conductivity measurement, cyclic voltammetry (CV), and elemental analyses. The molar conductance of oxovanadium(IV) complexes were found to be relatively low, depicting their non-electrolytic nature. The XRD patterns reveal the size of particles to be 47.53 nm and 26.28 nm for the two complexes in the monoclinic crystal system. The molecular structures, geometrical parameters, chemical reactivity, stability, and frontier molecular orbital pictures were determined by density functional theory (DFT) calculations. The theoretical vibrational frequencies and EPR g-factors (1.98) were found to correlate well with the experimental values. A distorted square pyramidal geometry with C₂ symmetry of the complexes has been proposed from experimental and theoretical results in a synergistic manner. The antimicrobial sensitivity of the ligands and their metal complexes assayed in vitro against four bacterial pathogens viz. Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella Typhi showed that the oxovanadium(IV) complexes are slightly stronger antibacterial agents than their corresponding Schiff base precursors. The binding affinities obtained from the molecular docking calculations with the receptor proteins of bacterial strains (2EUG, 3UWZ, 4GVF, and 4JVD) showed that the Schiff bases and their oxovanadium(IV) complexes have considerable capacity inferring activeness for effective inhibition. The molecular dynamics simulation of a protein-ligand (4JVD-HL₂) complex with the best binding affinity of -12.8 kcal/mol for 100 ns showed acceptable stability of the docked pose and binding free energy of -15.17 ± 2.29 kcal/mol from molecular mechanics-generalized Born surface area (MM-GBSA) calculations indicated spontaneity of the reaction. The outcome of the research shows the complementary role of computational methods in material characterization and provides an interesting avenue to pursue for exploring new triazole based Schiff's bases and its vanadium compounds for better properties.

A New MBH Adduct as an Efficient Ligand in the Synthesis of Metallodrugs: Characterization, Geometrical Optimization, XRD, Biological Activities, and Molecular Docking Studies

This article reports the synthesis, characterization, geometrical optimization, and biological studies of new MBH-based organometallic compounds of medicinal significance. The ligand (MNHA) was prepared via the Morita-Baylis-Hillman (MBH) synthetic route, from aromatic aldehyde containing multiple functional groups. Metal complexes were prepared in an alkaline medium and under other suitable reaction conditions. Spectral and elemental analyses were used to identify the structural and molecular formulas of each compound. Optimized geometry was determined through density functional theory (DFT) B3LYP and 6-311++ G (d,p) basis set for the MBH adduct, whereas structures of novel complexes were optimized with the semi-empirical PM6 method. Powder XRD analysis furnished the crystal class of complexes, with Co³⁺, Cr³⁺, and Mn²⁺ being cubic, while Ni²⁺ was hexagonal, and Cu²⁺ was orthorhombic. Moreover, the ligand, along with Ni²⁺ and Co³⁺ complexes, showed profound antibacterial action against S. aureus, E. coli, B. pumilis, and S. typhi. Additionally, all of the complexes were shown to persist in the positive antioxidant potential of the ligand. Contrarily, not a single metal complex conserved the antifungal potentials of the ligand.

NSAID-Based Coordination Compounds for Biomedical Applications: Recent Advances and Developments

After the serendipitous discovery of cisplatin, a platinum-based drug with chemotherapeutic effects, an incredible amount of research in the area of coordination chemistry has been produced. Other transition metal compounds were studied, and several new relevant metallodrugs have been synthetized in the past few years. This review is focused on coordination compounds with first-row transition metals, namely, copper, cobalt, nickel or manganese, or with zinc, which have potential or effective pharmacological properties. It is known that metal complexes, once bound to organic drugs, can enhance the drugs’ biological activities, such as anticancer, antimicrobial or anti-inflammatory ones. NSAIDs are a class of compounds with anti-inflammatory properties used to treat pain or fever. NSAIDs’ properties can be strongly improved when included in complexes using their compositional N and O donor atoms, which facilitate their coordination to metal ions. This review focuses on the research on this topic and on the promising or effective results that complexes of first-row transition metals and NSAIDs can exhibit.

Potential applicability of Schiff bases and their metal complexes during COVID-19 pandemic – a review

The rapid growth and revolution in the area of emerging therapeutics has been able to save the life of millions of patients globally. Besides these developments, the microbes are consistently struggling for their own survival and hence becoming quite more sturdy and incurable to existing drugs. Covid-19 virus and Black Fungus are recent examples of failure of medical preparations and strength of these viruses beyond the imagination of medical practitioners. Henceforth the study has made an extensive survey of exiting literature on heterocyclic schiff bases and their transition metal complexes to look for their potential applicability as antimicrobial agents. The inherent physiognomies of the essential properties of these transition metal complexes including thermodynamic, kinetic and chelating are comparatively modifiable as per requirements. The study has found that the biological applications of these transition metal complexes are well suited to be used as antibacterial and antifungal agents.

A hemilabile 2-(2′-pyridyl)-imidazole based nickel(ii) complex: proton-coupled-electron-transfer, bactericidal and cytotoxicity studies

This study deals with the synthesis, structural characterization, proto-coupled-electron-transfer, bactericidal and cytotoxicity study of a hemilabile and water-soluble 2-(2′-pyridyl)-imidazole nickel(ii) complex.

Assessing Density Functional Theory for Chemically Relevant Open-Shell Transition Metal Reactions

Due to the principle lack of systematic improvement possibilities of density functional theory, careful assessment of the performance of density functional approximations (DFAs) on well-designed benchmark sets, for example, for reaction energies and barrier heights, is crucial. While main-group chemistry is well covered by several available sets, benchmark data for transition metal chemistry is sparse. This is especially the case for larger, chemically relevant molecules. Addressing this issue, we recently introduced the MOR41 benchmark which covers chemically relevant reactions of closed-shell complexes. In this work, we extend these efforts to single-reference open-shell systems and introduce the "reactions of open-shell single-reference transition metal complexes" (ROST61) benchmark set. ROST61 includes accurate coupled-cluster reference values for 61 reaction energies with a mean reaction energy of -42.8 kcal mol^-1. Complexes with 13-93 atoms covering 20 d-block elements are included, but due to the restriction to single-reference open-shell systems, important elements such as iron or platinum could not be taken into account, or only to a small extent. We assess the performance of 31 DFAs in combination with three London dispersion (LD) correction schemes. Further, DFT-based composite methods, MP2, and a few semiempirical quantum chemical methods are evaluated. Consistent with the results for the MOR41 closed-shell benchmark, we find that the ordering of DFAs according to Jacob's ladder is preserved and that adding an LD correction is crucial, clearly improving almost all tested methods. The recently introduced r²SCAN-3c composite method stands out with a remarkable mean absolute deviation (MAD) of only 2.9 kcal mol^-1, which is surpassed only by hybrid DFAs with low amounts of Fock exchange (e.g., 2.3 kcal mol^-1 for TPSS0-D4/def2-QZVPP) and double-hybrid (DH) DFAs but at a significantly higher computational cost. The lowest MAD of only 1.6 kcal mol^-1 is obtained with the DH DFA PWPB95-D4 in the def2-QZVPP basis set approaching the estimated accuracy of the reference method. Overall, the ROST61 set adds important reference data to a sparsely sampled but practically relevant area of chemistry. At this point, it provides valuable orientation for the application and development of new DFAs and electronic structure methods in general.

Antibacterial Thiamine inspired silver (I) and gold (I) N-heterocyclic carbene compounds

Three new coinage metal carbene complexes of silver and gold were synthesized from a thiamine inspired proligand. The compounds were characterized by HRMS, NMR spectroscopy (1H, 19F, 31P and 13C), FT-IR and elemental analysis. The coordination environment around the metal centers was correlated to the diffusion coefficients obtained from DOSY-NMR experiments and was in agreement with the nuclearity observed in the solid-state by single crystal X-ray crystallography. The silver and gold carbene compounds were subjected to MIC studies against a panel of pathogenic bacteria, including multidrug resistant strains, with the gold carbene derivative showing the most potent antimicrobial activity against Gram-positive methicillin resistant Staphylococcus aureus (MRSA).

Synthesis of New Naphthyl Aceto Hydrazone-Based Metal Complexes: Micellar Interactions, DNA Binding, Antimicrobial, and Cancer Inhibition Studies

In the present study, naphthyl acetohydrazide (HL) ligand was prepared and used for the synthesis of new six amorphous transition metal (Co(II), Ni(II), Cu(II), Zn(II), Pb(II), Cd(II)) complexes. All the compounds were characterized by elemental analysis, UV-vis, FT-IR, ¹H- and ¹³C-NMR, and Matrix-Assisted Laser Desorption Ionization (MALDI). The solubilization study was carried out by estimating the interaction between the metal complexes with surfactants viz. sodium stearate (SS) and Cetyltrimethylammonium bromide (CTAB). UV-Visible spectroscopy was employed to determine partitioning and binding parameters, whereas electrical conductivity measurements were employed to estimate critical micellar concentration (CMC), the extent of dissociation, and free energy of micellization. The CT-DNA interaction of synthesized compounds with DNA represents the major groove binding. The synthesized ligand and metal complexes were also tested against bacterial and fungal strains and it has been observed that Cu(II) complex is active against all the strains except Candida albicans, while Cd(II) complex is active against all bacterial and fungal strains except Pseudomonas. Among all compounds, only the Pd(II) complex shows reasonable activity against cervical cancer HeLa cell lines, representing 97% inhibition.

Biologically relevant and energetically significant cooperative ternary (π–π)2/(π–π)1/(π–π)2 assemblies and fascinating discrete (H2O)21 clusters in isostructural 2,5-pyridine dicarboxylato Co(ii) and Zn(ii) phenanthroline compounds: antiproliferative evaluation and theoretical studies

Cytotoxicity in cancer cells with structure activity relationship has been explored in isostructural Co(ii) and Zn(ii) compounds involving energetically significant cooperative (π–π)₂/(π–π)₁/(π–π)₂ assemblies and fascinating (H₂O)₂₁ clusters.

Transition metal complexes as potential tools against SARS-CoV-2: anin silicoapproach

Screening of selected transition metal-based antiviral agents,in silico, predicted the potential inhibition of RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 which emerged as the potential drug candidate for COVID-19.

Synthesis, structure and characterization of new dithiocarbazate-based mixed ligand oxidovanadium(iv) complexes: DNA/HSA interaction, cytotoxic activity and DFT studies

The synthesis, structure and characterization of mixed ligand oxidovanadium(iv) complexes [V^IVOL^1–2(L^N–N)] (1–3) are reported. With a view to evaluating their biological activity, their DNA/HSA interaction and cytotoxicity activity have been explored.

Heteroleptic Metal Complexes of a Pyrimidinyl Based Schiff Base Ligand Incorporating 2,2'-Bipyridine Moiety: Synthesis, Characterization, and Biological Studies

A sequence of transition metal complexes of Mn(II), Co(II), Ni(II), and Cu(II) incorporating a novel pyrimidinyl based Schiff base ligand, 2-(4,6-dimethylpyrimidin-2-ylamino)naphthalene-1,4-dione (HL) and 2,2′-bipyridine has been synthesized and characterized using elemental, magnetic, conductance, infrared (FT-IR), nuclear magnetic resonance (¹H- and ¹³C-NMR), electronic (UV-Vis), electrospray ionization mass spectrometry (ESI-MS), thermographic analysis (TGA), and molecular docking studies. The acquired results were consistent with the adoption of the chemical formula, [M(X)(L)(Y)]·nH₂O (where M = Mn, Co, Ni, and Cu; L = Schiff base; X = 2,2′-bipy; Y = OAc; and n = 0,1) for the metallic complexes. HL ligand acts as a bidentate chelator and coordinates to metallic ion centre through carbonyl oxygen atom and deprotonated imide nitrogen. Similarly, 2,2′-bipy acts as a non-ionic bidentate chelator coordinating to metallic ion center via two nitrogen atoms. The mixed ligand complexes were appraised against pathogenic strains: S. aureus, P. aeruginosa, E. coli, B. cereus, P. mirabilis, K. oxytoca, A. niger, A. flevus, and R. Stolonifer. The antimicrobial studies gave moderate-good activity. Molecular docking studies on these compounds were done to indicate binding interactions between the compounds and adopted drug targets. Additionally, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the compounds were determined at different concentrations. The antioxidant study showed good radical scavenging abilities.

Density functional theory molecular modelling, DNA interactions, antioxidant, antimicrobial, anticancer and biothermodynamic studies of bioactive water soluble mixed ligand complexes

A novel series of bioactive water soluble mixed ligand complexes (1-5) [M^II(L)(phen)AcO]. nH₂O {where M = Cu (1) n = 2; Co (2), Mn (3), Ni (4), n = 4 and Zn (5) n = 2} were synthesized from 2-(2-Morpholinoethylimino) methyl)phenol Schiff base ligand (LH), 1, 10-phenanthroline and metal(II) acetate salt in a 1:1:1 stoichiometric ratio and characterized by several spectral techniques. The obtained analytical and spectral data suggest the octahedral geometry around the central metal ion. Density functional theory calculations have been further supportive to explore the optimized structure and chemical reactivity of these complexes from their frontier molecular orbitals. Gel electrophoresis result indicates that complex (1) manifested an excellent DNA cleavage property than others. The observed binding constants with free energy changes by electronic absorption technique and DNA binding affinity values by viscosity measurements for all compounds were found in the following order (1) > (2) > (4) > (5) > (3) > (LH). The binding results and thermodynamic parameters are described the intercalation mode. In vitro antioxidant properties disclose that complex (1) divulges high scavenging activity against DPPH^•, ^•OH, O₂^-• NO^•, and Fe³⁺. The antimicrobial reports illustrate that the complexes (1-5) were exhibited well defined inhibitory effect than ligand (LH) against the selected different pathogenic species. The observed percentage growth inhibition against A549, HepG2, MCF-7, and NHDF cell lines suggest that complex (1) has exhibited superior anticancer potency than others. Thus, the complex (1) may contribute as potential anticancer agent due to its unique interaction mode with DNA.GRAPHICAL ABSTRACT Communicated by Ramaswamy H. Sarma.

Regression of murine Ehrlich ascites carcinoma using synthesized cobalt complex

Cisplatin as a chief chemotherapy has nephro-toxicity and so we have tried to develop a novel antitumor drug based on a combination of cobalt metal ion with an organic moiety. The antitumor activity of the complex was tested in vitro and in vivo against murine Ehrlich ascites carcinoma (EAC). Antioxidant capacity and nucleic acids content were determined. Cobalt(ii) diacetyl monoxime-2-hydrazinopyridine complex significantly diminished tumor load. It decreased the tumor proliferation rate and obviously increased the life span of EAC-bearing mice. It reversed the haematological parameters back towards normal, reduced liver enzymes and urea, and increased albumin and total protein. Antioxidant parameters levels were reversed towards normal. An assessment was conducted by comparing these results with those obtained using the standard drug, cisplatin. The results suggest that the cobalt complex can be considered as a potent anticancer agent as it showed appreciable antitumor activity in EAC-bearing mice that was almost analogous to that of the reference standard, cisplatin.