Azomethine Nitrogen Research Articles

Biological evaluation of nano-sized novel Schiff base ligand-based transition metal complexes

This study reports on the preparation, characterization, and biological evaluation of nano-sized novel Schiff base ligand (SBL) based transition metal complexes, which were synthesized by reacting metal chloride salts with SBL. The SBL and its complexes were characterized using different analytical and spectroscopic techniques including 1H - 13C NMR, UV–Vis, IR, CHN elemental analysis, TGA, DTA, SEM, TEM, XRD, ICP-MS, molar conductivity, and magnetic susceptibility. The characterization results showed that the complexes had formula [MLCl2 (H2O)2], where M = V3+ and Cr3+ or [M(L)2(H2O)2], where M = Mn2+, Ni2+, Zn2+ and Cd2+. The ligand behaved as a monobasic bidentate chelator bonding the metal via the deprotonated hydroxyl oxygen and azomethine nitrogen, adopting a distorted octahedral structure. XRD spectroscopy and SEM confirmed the complexes to be crystalline, with particle sizes ranging from 50 to 100 nm. The prepared nano-compounds were evaluated for their in vitro antimicrobial, antifungal, and anticancer activities, as well as in vivo oral toxicity tests. In-vitro antimicrobial activities demonstrated that the Zn2+ complex was the most active against bacteria, while the Cr3+ complex was the most active against fungi. The V3+ complex was shown to be the least active against all microorganisms tested. Moreover, the Zn2+ complexes showed the most effective anticancer activity against WI38 and MCF-7 cell lines with IC50 values of 39.82 and 7.31 µM, respectively, while, the Cr3+ complex was the most effective against the HEPG-2 cell line with an IC50 of 11.83 µM. In addition, in vivo, oral toxicity of (SBL) ligand and its metal complexes showed a safety limit of up to 2000 mg/kg of rat’s dose in the level of liver and kidney histology and hematology and biochemical analysis. We concluded that these novel nano-synthesized complexes can used in therapeutics to avoid microbial resistance problems.

Synthesis, Crystal Structure Determination and Magnetic Study of a New [2 × 2] Grid Tetranuclear Fe(II) and Ni(II) Complexes Derived from the Ligand 1, 5-Bis(1-(Pyridin-2-Yl) Ethylidene) Carbonohydrazide)

Complexes of nickel (II) and iron (III) are easily synthetized using the symmetrical ligand 1,5-bis(1-(pyridin-2-yl)ethylidene)carbonohydrazide) (H2L) and metal nitrate salts. Square [2x2] grids structure of one tetranuclear iron and one tetranuclear nickel complex were isolated. X ray diffraction analysis reveals that the crystal structures of the two complexes are similar. The asymmetric unit of each complex consists of four cationic ligand molecules and four metal ions. Each ligand acts in its monodeprotonated form through five coordination sites such as two pyridine nitrogen atoms, two azomethine nitrogen atoms and one oxygen atom. Each of the four ligand molecules acts as a bridge between two metal ions yielding a square 2 x 2 grid structure. Each of the metal ion is hexacoordinated and is situated in a N4O2 core and the environment is best described as a severely distorted square bipyramidal geometry. Electrochemical studies show two electrons process for complex 1 and one electron process for complex 2. Variable temperature magnetic study shows that antiferromagnetic coupling is stronger in the nickel(II) than in the iron(II) complex. Perfect correlation between the magnetic properties and the crystallographic data are observed in both complexes.

Spectroscopic studies, antimicrobial activity, and computational investigations of hydrazone ligands endowed metal chelates

Our current efforts are aimed to synthesize 16 complexes of Co (II), Ni (II), Cu (II), and Zn (II) metal ions from heterocyclic hydrazone ligands by condensation reaction of 2,6‐diacetylpyridine with hydrazide derivatives to find out combating agent against microorganism diseases. The synthesized compounds were precisely characterized by various physicochemical and spectroscopic techniques like FT‐IR, UV–Vis, 1H and 13C NMR, magnetic susceptibility, ESR, mass spectrometry, powder XRD, TGA, and SEM that suggested the octahedral geometry of the complexes coordinating via enolic oxygen atoms, azomethine nitrogen atom, pyridine ring nitrogen atom of the hydrazone ligands, and oxygen atom of water molecule. The thermal stability of the complexes was demonstrated by thermal analysis revealing two‐step decompositions leaving behind metal oxide as an end residue. By using serial dilution method, the compounds (1–20) were tested for in vitro antimicrobial activity against four bacterial and two fungal pathogens. Among all the synthesized compounds, complex 16 was most active against B. subtilis, whereas complexes 13, 14, and 15 were most efficient for C. albicans. Moreover, the biological efficacy of H2L3 (3) ligand and its (13–16) complexes were demonstrated by computational methods like molecular docking, MESP, DFT, and ADMET studies that highlight that complexes have more potency than the ligands and may be employed as effective drug for pathogen‐induced malformations.

Structural and biological studies of mononuclear metal (II) complexes containing hetero ligand based on 3‐acetylpyridine thiosemicarbazone

The Schiff base (3‐APT) was a bidentate ligand produced from the condensation between 3‐acetylpyridine and the amine group of thiosemicarbazide. Metal chelates were successfully obtained with formulas [Cu(3‐APT)2X]X, [Ni(3‐APT)2]X2.H2O and [Pd(3‐APT)X2] (where 3‐APT = 3‐acetylpyridine thiosemicarbazone and X = Cl−). The characterization was performed by various physicochemical tools. The studied (3‐APT) ligand had two donor sites through both azomethine nitrogen and thiocarbonyl sulfur. The characterization tools observed the presence of two different geometric shapes. The square planar structure in the case of both nickel (II) and palladium (II) chelates and the square pyramidal structure in the case of copper (II) complex. The characterization involved a 1HNMR study for the (3‐APT) ligand and its square planar Pd (II) and Ni (II) chelates. The density functional theory was used to structurally optimize the synthesized ligand and its chelates. The antibacterial activity was evaluated using different types of bacteria showing superior results. The breast (MCF‐7) cell line was selected to investigate the cytotoxic effect of formed compounds. The palladium (II) complex was the most cytotoxic effective compound with the least IC50 value. Further theoretical molecular docking study was performed to observe the active sites in the selected proteins during their interactions with our compounds.

Antimicrobial study of ruthenium and iridium half-sandwich complexes containing fluorenyl hydrazonothiazole derivative ligands

A series of six new hydrazineyl-thiazolyl mononuclear complexes (1–6) of the type [(arene)M(κ2 (N∩N)-L)Cl] (M = Ru, Ir, arene: p-cymene or Cp* (pentamethyl cyclopentadienyl); L = bidentate substituted thiazolyl derivatives) have been synthesized and characterized. The complexes have been isolated as neutral mononuclear N∩N chelating metal complexes. Complexes 1–6 were characterized by IR, UV–Vis, NMR, and ESI-MS spectral methods. The solid-state molecular structures of 3 and 4 were determined using single-crystal X-ray diffraction and the geometry of the complexes are pseudo-octahedral, similar to piano stool structures. The N∩N binding mode is through the azomethine nitrogen and the nitrogen of the thiazole ring, forming a five-membered chelating ring. The synthesized ligands and complexes were then tested for their antibacterial properties against three strains of bacterial microorganisms, Staphylococcus aureus (+ve), Klebsiella pneumoniae (−ve), and Escherichia coli (−ve).

Synthesis, crystal structures, and NMR (1H, 13C) spectroscopy of PdII/HgII complexes with N, S-donor thiosemicarbazone/heterocyclic-2-thione ligands

The reaction of 2-benzoylpyridine thiosemicarbazone, {(C6H5)(py-N1)C2=N2-N3H-C1(=S)-N4H2, bzpytscH}, with palladium(II) chloride in acetonitrile yielded a heteroleptic complex, [Pd(N1,N2,S-bzpytsc)Cl] (1), in which the thio-ligand coordinated through pyridyl nitrogen (N1), azomethine nitrogen (N2) and sulfur as terdentate anion (N,N,S-bzpytsc–). In another reaction, pyrimidine-2-thione (pymtH) with mercury(II) chloride in CH3CN-DMF mixture formed a homoleptic compound, [Hg(N,S-pymt)2] (2), similar to the literature report of formation of a homoleptic compound, [Hg(κ1S-pyt)2], from HgCl2 and pytH in CH3CN-DMF. A reaction of mercury(II) bromide with pyridine-2-thione (pytH) in CH3CN-DMF mixture did not remove the bromides and rather yielded a heteroleptic complex of composition, [HgBr2(κ1S-pytH)2] (3). NMR (1H, 13C NMR) spectroscopy and infrared spectroscopy of 1–4 as well as crystal structures of 1, 3, and 4 are reported.

Synthesis and Characterization of 4-amino-N'-[(1E)-1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene]benzohydrazide and its Cu(II), Ni(II), Zn(II) and Mn(II) Complexes

New benzohydrazone compound, 4-amino-N'-[(1E)-1-(2-hydroxy-6-methyl-4-oxo-4H-pyran-3-yl)ethylidene] benzohydrazide (HL1) and its Cu(II), Ni(II), Zn(II) and Mn(II) complexes were synthesized. The structures of HL1 and its complexes were elucidated by elemental analysis and IR, UV-Vis, 1H and 13C NMR spectroscopy and mass spectrometry. The infrared spectral data of the complexes revealed that HL1 coordinated with the metal ions through azomethine nitrogen, enolic oxygen and amide carbonyl oxygen atoms, hence, HL1 behaves as a monobasic tridentate ligand. UV-Vis data revealed that Zn(II) and Mn(II) complexes adopted octahedral geometry, while Cu(II) and Ni(II) complexes had five-coordinate and square-planar geometries respectively. The mass spectra data and elemental analysis values are in accordance with the calculated values for the suggested molecular formula of the complexes, a confirmation of the 1:1 ligand to metal stoichiometry in case of Cu(II) complex and 2:1 ligands to metal stoichiometry in case of the other complexes.

Iron(II) and cobalt(II) Complexes of 3,4‐Dihydroxybenzaldehyde‐4‐ethylthiosemicarbazone: Synthesis, Spectral Studies and Molecular Docking

AbstractFe(II) and Co(II) complexes of 3,4‐dihydroxybenzaldehyde 4‐ethylthiosemicarbazone were synthesized and characterized by elemental analysis (CHNS), magnetic susceptibility measurements, molar conductivity, Fourier transform infrared (FT‐IR), nuclear‐magnetic resonance (1H‐NMR and 13C‐NMR) and ultraviolet‐visible (UV‐Vis) spectra. The spectral and analytical data revealed that the obtained thiosemicarbazone‐metal complexes have tetrahedral geometry around the metal center. The studied ligand acts as a bidentate ligand by using both azomethine nitrogen and thiol sulphur as monoanion center of donation. To predict the reactive sites for electrophilic and nucleophilic attack, the Molecular Electrostatic Potential (MEP) was determined. The antibacterial activities of 3,4‐dihydroxybenzaldehyde 4‐ethylthiosemicarbazone ligand and its complexes were tested by molecular docking technique into the crystal structure of topoisomerase II and topoisomerase IV proteins. Molecular docking investigation proved that, the ligand and its complexes had interesting interactions with active sites of amino acids of the target proteins. The Co(II) complex exhibited better potential inhibition than other studied compounds.

Chemical Synthesis, Characterization and DNA Binding Studies of 2, 4- Dihydroxy Acetophenone Pramipexole Schiff Base Metal Complexes

Schiff and their complexes are versatile compounds synthesized from the condensation of an amino compound with carbonyl compounds and widely used for industrial purposes and also exhibit a broad range of biological activities, including antifungal, antibacterial, anti-malarial, ant proliferative, anti-inflammatory, antiviral, and antipyretic properties. Many Schiff base complexes show excellent activity in various reactions in the presence of moisture. Over the past few years, many reports have been on their applications in homogeneous and heterogeneous catalysis. The influence of certain metals on the biological activity of these compounds and their intrinsic chemical interest as multidentate ligands has prompted a considerable increase in the study of their coordination behavior. The development of new chemotherapeutic Schiff bases and their metal complexes is now attracting the attention of medicinal chemists. The present paper deals with synthesizing and characterizing metal complexes of new Schiff bases derived from Pramipexole (4, 5, 6, 7-Tetrahydro-N6-propyl-2, 6-benzothiazole diamine) and 2,4- dihydroxy acetophenone (2,4 DHAP) by using modified Sand Mayer's method. Synthesized complexes were characterized by several techniques using IR, 1HNMR, UV-visible spectrometry, TG-DTA, and Conduct Metric Titrations. Infrared spectral data indicate the coordination between ligand and central metal ion through deprotonated phenolic oxygen and azomethine nitrogen. In addition, the authors have screened the compounds for DNA binding studies. It was found that these complexes bind DNA with high affinities.

Reactions of Group VIB metal carbonyls with two novel rigid macrocyclic Schiff base ligands incorporating acridine inter-crossing group

Two new rigid macrocyclic Schiff base ligands incorporating acridine inter-crossing group [1,1′-(acridine-3,6-diylbis(azaneylylidene))bis(methaneylylidene))bis(naphthalen-2-ol), L1, and N,N'-(acridine-3,6-diyl)bis(1-(quinolin-2-yl)methanimine), L2, were synthesized and fully characterized. The X-ray single crystal analysis of L1 explored that the compound crystallized in a monoclinic crystal system with a space group P21/c. The compound was crystalized with five water molecules. Interestingly, L1 occurred as a double zwitterion, where the hydrogen of the OH group of the hydroxynaphthalene transferred to the azomethine nitrogen to form NH+ and O− moieties with the presence of hydrogen bonding between them. Hirshfeld surface analysis of the L1 was also investigated. Reactions of the two ligands with the Group VIB metal carbonyls in air were investigated. In order to characterize the novel compounds, various analytical and spectroscopic methods were used. The analysis revealed that the complexes were formed as oxo derivatives with unique structural features. The presented compounds conducted fluorescence quenching investigations, viscosity evaluations, antimicrobial and antioxidant properties. It was concluded that the binding interaction with DNA was electrostatic binding mode rather than intercalative mode. Molecular docking of L1 and its complexes were investigated versus three macromolecular receptors (PDB: 4BJP, 1BQB and 1BNA). These targets were selected to compare the experimental biological data with the results of the docking analysis.

3-acetyl-coumarin-substituted thiosemicarbazones and their ruthenium, rhodium and iridium metal complexes: An investigation of the antibacterial, antioxidant and cytotoxicity activities

A series of ruthenium, iridium and rhodium half-sandwich complexes containing 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone derivatives have been prepared for use as antibacterial and anticancer agents. These complexes have been isolated as cationic bidentate (N, S) and neutral bidentate (N, S) complexes. The complexes have been characterized by spectral techniques (FT-IR, UV-Vis, NMR and HRMS) and single-crystal X-ray crystallography methods. The structure of complex 6 has been determined by a single-crystal X-ray diffraction study, which shows that coordination of the 3-acetyl chromen-2-one-4(N)-substituted thiosemicarbazone ligand to the metal occurs via azomethine nitrogen and thiolate sulfur atoms. Vitro antibacterial activity against gram-positive Staphylococcus aureus and gram-negative Escherichia coli, Klebsiella pneumonia strains and antioxidant activity have been evaluated. Also, the said complexes were tested for anticancer efficacy (in vitro for 48h) in Dalton's lymphoma (DL) cancer cell lines using cell cytotoxicity (MTT) and apoptosis tests. The results were compared with cisplatin (standard drug) under identical experimental conditions. The cell cytotoxicity results showed that complex 5 induced higher cytotoxicity in DL cells, followed by complex 4, 1, and 2.

Synthesis, Characterization, Antimicrobial and Antimalarial Activities of Azines Based Schiff Bases and their Pd(II) Complexes.

Herein, we report synthesis, characterization, antimicrobial and antimalarial activities of azines Schiff base ligands (L1 -L4 ) and their palladium (II) complexes (C1 -C4 ) of [Pd(L)(OAc)2 ] type. The azine ligands (L1 -L4 ) were prepared by condensation of carbonyl compounds with hydrazine hydrate and their complexes by the reaction of palladium acetate with L1 -L4 ligands in 1 : 1 molar ratio. The prepared ligands and their complexes were characterized by spectral characterization using 1 H &13 C-NMR, FT-IR and mass spectral studies, which revealed that the ligands coordinates via azomethine nitrogen and heteroatom or aryl carbon with palladium. Moreover, Schiff bases and their palladium (II) complexes have been screened for their antibacterial (S. aureus, B. subtillis, and S. typhi, P. aeruginosa), antifungal (C. albicans, A. niger, and A. clavatus) and antimalarial (P. falciparum) activities. The Schiff base L4 showed good results for antibacterial against S. aureus (MIC, 50 μg/mL) and antimalarial against P. falciparum (IC50 , 0.83 μg/mL). The complex C1 showed best antibacterial activity (MIC, 62.5 μg/mL) against S. typhi and the complex C4 exhibited remarkable antimalarial activity (IC50 , 0.42 μg/mL) among the tested compounds. Thus, azines based ligands and their Pd complexes can be good antimicrobial and antimalarial agents if explored further.

Synthesis and characterization of tailor-made o-hydroxysubstituted anils through 1H NMR, ­13C NMR, SC-XRD and DFT studies for possible optoelectronic applications

The present work reports the synthesis of two simple tailor-made anils (o-hydroxybezylidene-orthochloroaniline & o-hydroxynaphthalidene-orthochloroaniline) and their characterization by 1H & 13C Nuclear magnetic resonance(NMR), single X-ray diffraction spectroscopy(SC-XRD) and DFT studies. DFT-B3LYP optimized the molecular structures with a 6-311G (d, p) basis set to accomplish the global minimum energy state. 1H NMR confirmed the occurrence of H-bonding between the phenolic hydrogen and azomethine nitrogen in both molecules, further supported by SC-XRD analysis and DFT studies. The structural parameters such as bond angle, bond length, and dihedral angle derived from the optimized structure of molecules with C1 symmetry were compared with the corresponding parameters extracted from the ORTEP diagrams for both anils. Appreciable harmony of the structural parameters was achieved between these two analyses, confirming the anils’ purity. Slight discrepancy observed between DFT and SC-XRD analyses was attributed to the difference in the state of the molecules. Geometric optimization indicated the molecules to be coplanar. The MEP surface and atomic charges on the atoms envisaged the electron population and charged sites of the anils. Conclusively, both the anils have a suitable structural hierarchy for superior electron transport from the phenyl rings over the entire molecular framework suitable for optoelectronics applications.

Ruthenium, rhodium, and iridium complexes featuring fluorenyl benzohydrazone derivatives: Synthesis and preliminary investigation of their anticancer and antibacterial activity

A convenient synthesis of twelve complexes (1–12) of ruthenium(II), rhodium(III) and iridium(III) containing fluorenyl benzohydrazone ligands having the general formula [(arene)M(L)Cl] (arene: benzene/p-cymene/Cp*; l-bidentate substituted benzoyl hydrazone derivatives) has been carried out. The characterization of the complexes has been done by FT-IR, UV–Vis, NMR and X-ray crystallographic studies. The metal complexes exhibit N∩O binding mode through the azomethine nitrogen and the imidolate oxygen forming a five-membered chelating ring. All the compounds were tested for their antibacterial properties against three strains of bacterial microorganisms - Staphylococcus aureus (+ve), Klebsiella pneumoniae (-ve) and Escherichia coli (-ve). In-vitro assay results further revealed that complexes 4 and 6 significantly act against Gram-positive (Staphylococcus aureus) and Gram-negative (E. coli and Klebsiella pneumoniae). An in-vitro assessment of the cytotoxic effects of both the complexes and ligands was performed, and the findings indicate that complex 9 exhibited the most promising results with the lowest IC50 value in terms of cell viability percentage against HeLa cell lines. These results highlight the potential of further investigating the anticancer properties of this particular complex.

Preparation, Characterization of Some Lanthanide(III) Complexes of N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide

The present investigation describes the synthesis and structural study of the ligand N'-(phenyl(pyridin-2-yl)methylene)nicotinohydrazide (HL), which was used to generate two type complexes formulated as [Ln(HL)2(NO3)2(H2O)].(NO3) (Ln = La (1) and Pr (2)) and [Ln(HL)2(NO3)(H2O)2].(NO3)2 (Ln = Nd (3), Sm (4), Gd (5) and Tb (6)). The ligand and the complexes are characterized by NMR, UV-Visible and FTIR spectroscopies, conductivity measurements and room temperature magnetic moment measurements. The [La(HL)2(NO3)2(H2O)].(NO3) compound crystallizes in the orthorhombic space group Pbcn with the following unit cell parameters: a = 16.8634(8) Å, b = 8.0615(4) Å, c = 30.2833(15) Å, V = 4116.8(3) Å3, Z = 8, R1 = 0.049 and wR2 = 0.120. The structure reveals that two neutral ligand molecules in η3-mode, two bidentate nitrate groups in η2-mode and one water molecule coordinate the central La3+. Each organic molecules acts through one carbonyl oxygen atom, one azomethine nitrogen atom and one nitrogen atom from a pyridine ring. The lanthanide ion has a coordination number of 11 and the coordination environment can be described as distorted pentacapped trigonal prism. Numerous hydrogen bonds link the molecules into three-dimensional network.

Bivalent Metal Chelates with Pentadentate Azo-Schiff Base Derived from Nicotinic Hydrazide: Preparation, Structural Elucidation, and Pharmacological Activity.

Azo-Schiff base ligand (N'-((E)-2-hydroxy-5-((E)-(2-hydroxyphenyl)diazenyl)benzylidene)nicotinohydrazide) and its Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Pd(II) chelates were prepared and elucidated. The geometrical structures of the prepared chelates were characterized by several spectroanalytical techniques and thermogravimetric analysis. The obtained data revealed that the chelates have (1M:1L), (1M:2L), (1M:3L), and (1M:4L) molar ratios. The infrared spectra displayed that the H2 L ligand behaves in a pentacoordinate fashion in chelates of Mn(II), Ni(II), and Cu(II) ions. However, in Zn(II) and Pd(II) chelates, the ligand is coordinated as a tetradentate species (NONO) through nitrogen atoms of azomethine and azo groups as well as oxygen atoms of phenolic hydroxy, and carbonyl groups. Besides, it was concluded that the oxygen atoms of carbonyl and hydroxy groups along with the azomethine nitrogen atom of the ligand are bounded with Co(II) ion in metal chelate (2). According to the measured molar conductance values, the chelates of Cu(II), Zn(II), and Pd(II) are weak electrolytes, but Mn(II), Co(II), and Ni(II) chelates are ionic. The azo-Schiff base ligand and its prepared metal chelates were tested for their antioxidant and antibacterial properties. The Ni(II) chelate was found to be considered an effective antioxidant agent. In addition, the available antibacterial data suggest that the Ni(II) and Co(II) chelates may be employed as inhibitor agents against Proteus vulgaris, Escherichia coli, and Bacillus subtilis bacteria. Furthermore, the data showed that, in comparison to the ligand and other metal chelates, copper(II) chelate (4) exhibited higher action against Bacillus subtilis bacteria.

Synthesis, Physicochemical, and Antimicrobial Activity of Copper and Zinc Complexes with N, O - Bidentate Schiff Base

This paper is intended to prepare new antimicrobial complexes with proven efficiency. The Schiff base, through the condensation process of salicylaldehyde and p-toludine, and its Cu and Zn complexes were successfully synthesized. The Schiff base and its complexes were characterized using molar conductivity, Ultraviolet-visible (UV-Vis), atomic absorption spectroscopy (AAS), and Fourier transform infrared (FTIR) techniques. Accordingly, these characterizations not only confirmed that the synthesized Schiff base acted as N,O bidentate ligand (through azomethine nitrogen and phenoxide oxygen) and chelated with Cu(II) and Zn(II) in the metal-to-ligand ratio of 1:2 but also revealed the characteristic electronic-transition of π→π*/n→π* of the ligand, and ligand-metal charge transfer and d-d of the metal complexes. Moreover, both Cu and Zn complexes recorded weak molar conductance of 54.12 and 51.41 S cm2 mol-1, respectively. Further, their antibacterial activities were evaluated by disc diffusion assay against Staphylococcus aureus (gram-positive), Escherichia coli (gram-negative), and Bacillus cereus (gram-negative) bacteria. For all microbial, the metal complexes recorded higher activities than the parent ligand; such increased activity of the complexes may be due to the chelation of the metal ion in the complexes, which enhances the lipophylic character favoring its permeation through the lipid layer of the cell membrane. Such metal complexes can therefore be explored in the future as an option for decreasing the pathogenic potential of infecting bacteria.

Synthesis, characterization, photoluminescence properties, DFT studies, photocatalytic and antifungal activity of a new pyrazole-containing thiosemicarbazone ligand and its Co(III) and Ni(II) complexes

A new pyrazole-based thiosemicarbazone ligand, 5-methyl-3-formylpyrazole-N(4)-dipentylthiosemicarbazone (HMPzNPent2) (1), and its Co(III) and Ni(II) complexes, [Co(MPzNPent2)2]Br (2) and [Ni(HMPzNPent2)2]Cl2 (3), respectively, were synthesized and characterized. Complexes 2 and 3 are cationic in nature and behave as 1:1 and 1:2 electrolytes in MeOH, respectively. Electronic spectral features of the complexes indicate distorted octahedral structures. IR spectral data (4000–450 cm−1) suggest monoprotic tridentate (NNS) coordination of 1 to Co(III) via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulfur; In contrast, 1 is a neutral NNS tridentate donor in 3, coordinating to Ni(II) via the pyrazolyl iminic nitrogen, azomethine nitrogen and thioketo sulfur. Structural features of the compounds were confirmed by DFT calculations. TD-DFT absorption spectra authenticate that the simulated peaks are in reasonable agreement with the experimentally resolved peaks. Fluorescence spectral studies revealed photoluminescent behavior. The three compounds reported here have photocatalytic activity. 1 (used as positive control) and 3 show similar antifungal activity in inhibiting the growth of the phytopathogen Colletotrichum siamense (CS), whereas 2 is less efficient to control the growth of CS. Both 3 and 2 show antifungal activity against Colletotrichum gloeosporioides (AP2). Compound 3 is more effective to prevent the growth of phytopathogen Fusarium equisetum (F.E) than 2 and 1 (positive control).

Synthesis, spectral characterization and biological investigation of new organoruthenium(II) complexes with N, X-donor (X = S, O) heterocyclic chelators

New Ru(II) arene complexes containing 2,4-dihydroxyacetophenone based Schiff bases have been synthesized and characterized with FTIR, UV–visible, 1H NMR, 13C NMR and mass spectroscopies. Spectroscopic analysis revealed that the ligands coordinated to ruthenium(II) in a monobasic bidentate fashion via azomethine nitrogen and thiolate/oxalate. Antimicrobial activities of the compounds were evaluated with two bacteria (Staphylococcus aureus and Pseudomonas aeruginosa) and two fungi (Candida albicans and Candida tropicalis). The complexes displayed better antimicrobial activity over their ligands. In addition, the ligands and the complexes were analyzed for their anticancer potential against A549 (human lung carcinoma) and HeLa (human cervical cancer) cells, in which the complexes exhibited comparable activities against A549 (IC50 value is 21 ± 1 µM (1), 18 ± 1 µM (2)) and HeLa (IC50 value is 22.1 ± 0.9 µM (1), 20 ± 1 µM (2)) with the standard drug cisplatin (IC50 value is 25 ± 1 µM (A549) and 27 ± 1 µM (HeLa)). The non-toxic nature of the compounds has been confirmed with human umbilical vein endothelial cells (HUVEC cells). The obtained results highlighted the possibility of developing ruthenium arene complexes as anticancer agents.

Enaminoketones - functional derivatives based on 7-hydroxy-3′,3′-dimethyl-3′<i>H</i>-spiro[chromen-2,1′-isobenzofuran]-8-carbaldehyde with aromatic amines. physicochemical studies and biological activity

This research focuses on studying derivatives of 2-oxaindane spiropyran by its condensation with aromatic amines. The results showed that all the synthesized compounds are enaminoketones form in both solution and solid state. This is explained by the fact that during the formation of Schiff bases, the proton of the 7-hydroxyl group of the benzopyran part migrates to the azomethine nitrogen, which leads to the transition of the cyclic form of spiropyran into the corresponding enaminoketone. In the DMSO solution, the enaminoketones dynamic equilibrium of the E , Z -isomeric forms were observed. The structure of enaminoketone based on 3,4-dimethylaniline was proved by the X-ray diffraction method. The synthesized compounds were studied for their in vitro anticancer activity against human hepatocellular carcinoma (HepG2), breast carcinoma (MCF-7), lung cancer (A549), and carcinoma cells (KB). Enaminoketone with R = 3,4-СH3Ph is characterized by the highest activity, with IC50 values of 13.38 μM (KB). The results in vitro antioxidant activity test using 1,1-diphenyl-2-picrylhydrazyl (DPPH) indicated that enaminoketones were inactive.