Donor Schiff Base Ligand Research Articles

Unraveling the Potential of Mononuclear Zn(II) and Cu(II) Schiff Base Metal Complexes: Microwave‐Aided Synthesis, Theoretical Analysis and Application in Biomimetic Catalysis, CT‐DNA Interaction, and In Vitro Biological Assays

ABSTRACTGiven the widespread and diverse effects of transition metal ions such as copper and zinc in multiple biological processes, this research endeavor addresses herein the microwave‐aided synthesis of two novel tetradentate ONNO (L1) and tridentate NNO (L2) donor Schiff base ligands derived from 4,5‐dimethyl‐1,2‐phenylenediamine and 4‐bromo‐2‐hydroxybenzaldehyde in a 1:2 ratio and from 4,5‐dimethyl‐1,2‐phenylenediamine and 5‐methoxy‐2‐hydroxybenzaldehyde in a 1:1 ratio, with their respective zinc, ZnL1(1) and ZnL2(3), and copper, CuL1(2) and CuL2(4), Schiff base metal complexes, which are comprehensively characterized utilizing physiochemical and analytical techniques, along with geometry optimization using the DFT approach. Spectrophotometric analyses have been used to assess the biomimetic activity in the conversion of 3,5‐DTBC to 3,5‐DTBQ with turnover numbers 53.4 and 78 h−1 in methanol for 2 and 4, whereas the zinc complexes are found to be ineffective. With CT‐DNA, possible modes of interaction with the synthesized complexes have been explored using absorption spectroscopy, where the associated binding constants ranged between 1.541 × 105 and 2.186 × 105 M−1. EtBr‐bound DNA was used in the fluorescence quenching experiments with Stern–Volmer constant (Ksv) values in the range 4.084 × 104 and 3.402 × 104 M−1, showing a stronger association with CT‐DNA. The compounds' ability to inhibit bacterial strains was also examined in vitro, as well as their ability to reduce inflammation, through the protein denaturation method and the DPPH assay for antioxidant activity have been performed. Furthermore, molecular docking simulations have been carried out to obtain a deeper comprehension of the molecular‐level interactions with CT‐DNA and cyclooxygenase‐2 (COX‐2).

A New Azide-Bridged Polymeric Manganese (III) Schiff Base Complex with an Allylamine-Derived Ligand: Structural Characterization and Activity Spectra

This paper reports the synthesis and structural characterization of a novel azide-bridged polymeric manganese (III) Schiff base complex, using 2-((allylimino)methyl)-6-ethoxyphenol as a ligand. The crystal structure of the synthesized compound, elucidated by single-crystal X-ray diffraction analysis, indicates that it crystallizes in the monoclinic space group P21/c. The complex is found to display an octahedral geometry in which the central manganese Mn(III) coordinates with two bidentate donor Schiff base ligands via oxygen and nitrogen atoms. In addition, the metallic centers are linked together to form a one-dimensional chain bridged by end-to-end azide ligands. To offer a more thorough characterization of the synthesized compound, the study incorporates experimental data from FT-IR, UV-Vis, and cyclic voltammetry, alongside computational results from Hirshfeld surface analysis and DFT calculations conducted for both the ligand and complex. The computational analyses provided valuable insights into the intrachain and interchain interactions within the crystal structure, clarified the conformational characteristics of the isolated ligand molecule, and aided in the interpretation of the experimental IR spectra. Furthermore, an assessment of the compound’s drug-like properties was conducted using activity spectra for substances (PASS) predictions, revealing potential pharmacological activities.

Synthesis, Characterization, DNA, Fluorescence, Molecular Docking, and Antimicrobial Evaluation of Novel Pd(II) Complex Containing O, S Donor Schiff Base Ligand and Azole Derivative

Pd(II) with the Schiff base ligand 2-Hydroxy-3-Methoxy Benzaldehyde-Thiosemicarbazone (HMBATSC) (L2) and 2-aminobenzothiazole (2-ABZ) (L1) was synthesized. The Schiff base ligand and the Palladium(II) complex were characterized by C.H.N.S, FT-IR, conductance studies, magnetic susceptibility, XRD, and TGA. From the elemental analysis and spectral data, the complex was proposed to have the formula [Pd(HMBATSC)(2-ABZ)H2O]. The interaction between the Pd(II) complex and DNA was examined through various methods, including UV–Vis spectroscopy, fluorescence techniques, and DNA viscosity titrations. The findings provided strong evidence that the interaction between the Pd(II) complex and DNA occurs through the intercalation mode. The analysis yielded the following values: a Stern–Volmer quenching constant (ksv) of 1.67 × 104 M−1, a quenching rate constant (kq) of 8.35 × 1011 M−1 s−1, a binding constant (kb) of 5.20 × 105 M−1, and a number of binding the sites (n) of 1.392. DFT studies suggest that the azole derivative may act as an electron donor through pyridine nitrogen, while the Schiff base ligand may act as an electron donor via oxygen and sulfur atoms. TDDFT calculations indicate that the intramolecular charge transfer from the Schiff base to Pd(II) is responsible for the complex’s fluorescence quenching. The powder X-ray diffraction data revealed that the complex is arranged in a monoclinic system. The resulting Pd(II) complex was investigated for its antimicrobial activity and demonstrated antibacterial efficiency. Interestingly, it showed potent activity against E. coli and E. niger that was found to be more powerful than that recorded for Neomycin.

Theoretical and experimental demonstration of mononuclear Ni(II) and dinuclear Ni(III) complexes concerning their catalytic activity, DNA/ protein binding efficacy

The successful use of metal complexes in enzyme catalysis and biomedical applications boosts researchers to develop more and more metal-based compounds to inspect their said applications.In the present work one novel mononuclear Ni(II) [Ni(L1)2] (1) and one di nuclear Ni(III) complexes [Ni(L2)2(N3)2] (2) have been developed by utilizing N2O donor Schiff base ligand HL1 and N2O2 donor Schiff base ligand H2L2 respectively. The single crystal data analysis reveals that in complex 1 two deprotonated ligands coordinate to the Ni(II) forming a distorted octahedral geometry. The asymmetric unit of complex 2 comprises one deprotonated ligand (both the protons of phenolic –OH group were deprotonated), one azide anion, and one Ni(III). Two Ni(III) centers are connected via phenoxide bridging. Followed by the structural analysis the UV spectroscopic study is performed to understand the catecholase-like activity of the developed complexes by using 3,5-di-tertbutyl catechol (3,5-DTBC). The calculated turnover numbers (Kcat) for both complexes disclose the fact that complex2 is more susceptible to this catalytic process than 1. During the catalysis process, the production of Ni(II) in the case of complex2is favorable and this is the main factor to show its higher susceptibilitytowards the catalytic process. The biomedical applicability in terms of anticancer and antibacterial of complexes 1 and 2 is assessed by evaluating their interaction ability with DNA and HSA with the help of several spectroscopic approaches. The remarkably high complex-macromolecules binding constant values, obtained from electronic titration approve the binding efficacy of the target complexes (order ∼ 105). But if a tiny comparison is done then it is seen that complex 2 shows better DNA and HSA binding efficacy. The theoretical approach using molecular docking study fully validates the experimental findings.

New palladium(II) metallates containing ON donor Schiff base ligand. synthesis, spectral characterization, x-ray crystallography, photo physical and in vitro cytotoxicity

Two new Palladium(II) complexes were synthesized by reacting (3‑hydroxy-naphthalene-2-carboxylic thiophen-2-ylmethylene-hydrazide) with [PdCl2(EPh3)2] (E = P, As). The complexes [Pd(L-N,O)Cl(PPh3)] (1) [Pd(L-N,O)Cl(AsPh3)] (2), HL = 3‑hydroxy-naphthalene-2-carboxylicthiophen-2-ylmethylenehydrazide formation was analysed through various spectroscopic investigations (IR, Uv-Visble, 1HNMR ) and structural confirmation was obtained from single crystal x-ray crystallography, which indicated that the complex 1 having distorted square planar geometry. DNA/protein binding ability of the ligand and complexes were commenced using absorption and emission titrations and found that the complex 2 have better binding ability with tyrosine and tryptophan residues and by quenching the fluorescence of BSA through static quenching mechanism. Their antioxidant and in vitro anticancer activities were assessed, where complex 2 displayed better radical scavenging properties and cancer cell death inducing ability. Further, DAPI staining assay was performed to detect the mode of cell death and found complex 2 having better towards to cell death.

Cu(II)-Ln(III) (Ln = Gd, Tb and Dy) complexes of an unsymmetrical N2O3 donor ligand: field induced SMM behaviour of Cu(II)-Tb(III) complexes.

Three new hetero-metallic CuII-LnIII complexes [(CuL)Gd(NO3)3(CH3OH)]n (1), [(CuL)Tb(NO3)3(H2O)]·[CuL] (2) and [(CuL)Dy(NO3)3(H2O)]·[CuL] (3) have been synthesized using a mono-nuclear Cu(II) complex, [CuL], of an unsymmetrically di-condensed N2O3 donor Schiff base ligand, N-(3-methoxysalicylidene)-N-(salicylidene)-1,2-ethylenediamine (H2L). Single crystal X-ray crystallography revealed that complex 1 is a nitrate bridged 1D chain of dinuclear Cu(II)-Gd(III) units whereas in 2 and 3, the dinuclear Cu(II)-Ln(III) units are co-crystallized with a [CuL] unit. The Ln(III) centers are nine coordinated with the geometry of a spherical capped square antiprism for Gd and spherical tricapped trigonal prism for Tb and Dy. The geometry of the Cu(II) center is distorted octahedral for complex 1 and distorted square planar for complexes 2 and 3. Temperature-dependent molar magnetic susceptibility measurements in 1-3 revealed the presence of overall ferromagnetic coupling between the Cu(II) and Ln(III) centers. Notably, field induced single-molecule magnet behavior was witnessed in the Tb(III) derivative (2). The ab initio calculations indicated that upon application of an external magnetic field, the tunneling in the ground state of complex 2 gets reduced and thereby field-induced SMM behaviour is observed. Besides, in the case of complex 1, BS-DFT calculations were carried out to gain further insights into the magnetic exchange coupling interactions between the Cu(II) and Gd(III) centers.

NNO donor Schiff base metal complexes: Enzyme mimicking, DNA binding and biological insights

The present work focuses on the microwave-assisted synthesis, characterization and biological applications of a novel tridentate NNO donor Schiff base ligand derived from the condensation of 4-(Diethylamino)salicylaldehyde and 4,5-Dimethyl-1,2-phenylenediamine, along with its transition metal complexes of Cu(II) and Co(II) in 1:1 and 1:2 ratios each respectively. A theoretical basis for comprehending the electronic framework and characteristics of the complexes has been studied through the use of a computational approach. Further, the distorted octahedral geometry of the Schiff base metal complexes is confirmed by using analytical methods such as elemental analysis, molar conductance, ESI-MS, UV–Vis, FTIR, TGA and NMR spectra, which confirmed that NNO donor site of the ligand is coordinated with the metal ions. The complexes have been screened for their potential application as a catalyst for the catalytic conversion of 3,5-di‑tert‑butyl‑catechol (3,5-DTBC) to 3,5-di‑tert-butylquinone (3,5-DTBQ) and the turnover numbers (Kcat) have been found in the range 36.46–43.05 h−1 in methanol. Absorption spectroscopic technique has been employed to examine the possible modalities of interactions with the synthesized complexes using CT-DNA and the related binding constants exhibited in the range 2.58 × 104 M−1 to 1.98 × 105 M−1 thus depicting appreciable binding affinity. To evaluate the bioactivities, in-vitro assays for anti-oxidant and anti-inflammatory activity have also been implemented. The Cu(II) complex (CuL) has significant anti-oxidant activity and the Co(II) complex (CoL) has superior anti-inflammatory activity compared to all other complexes with IC50 values of 238.78 µM and 140.25 µM respectively. To better understand the molecular-level interactions and identify probable binding energies of inhibitors, molecular docking simulations have been performed.

Dihalosalicylaldehyde based molybdenum(VI) complexes: Synthesis, spectral characterization, crystal structures, and catalytic activities for the selective oxidation of benzylic alcohols

Three ONO donor Schiff base ligands were obtained by the condensation of 3,5-dihalosalicylaldehydes with nicotinoylhydrazide (H2Cl2SN: (E)-N'-(3,5-dichlorosalicylaldehyde) nicotinoylhydrazone, H2Br2SN: (E)-N'-(3,5-dibromosalicylaldehyde) nicotinoylhydrazone, and H2I2SN: (E)-N'-(3,5-diiodosalicylaldehyde) nicotinoylhydrazone on refluxing in ethanol. The treatment of [MoO2(acac)2] (acac = acetylacetonato) with these ligands in methanol afforded cis-dioxidomolybdenum(VI) complexes [MoO2(Cl2SN)(CH3OH)] (1), [MoO2(Br2SN)(CH3OH)] (2), and [MoO2(I2SN)(CH3OH)] (3). Various techniques like NMR (1H and 13C), FT-IR, Mass, TGA, elemental (CHN), and single-crystal X-ray diffraction analysis (for H2Cl2SN·H2O, 2a, [MoO2(Br2SN)(C2H5OH)], and 3a, [MoO2(I2SN)(H2O)].DMF) were utilized to characterize the synthesized compounds. The data collected from diffraction studies revealed that the geometry around Mo(VI) ions was distorted octahedral. Additionally, all complexes were successfully screened as catalysts for the selective oxidation of benzylic alcohols employing ethanol and hydrogen peroxide.

Indole-based NNN donor Schiff base ligand and its complexes: Sonication-assisted synthesis, characterization, DNA binding, anti-cancer evaluation and in-vitro biological assay

A novel indole based NNN donor Schiff base ligand and its Ni(II), Zn(II) and Cd(II) complexes have been synthesized using sonication-assisted method which is a highly efficient eco-friendly mechanism. The synthesized complexes have been characterized using elemental analysis, UV–Vis spectroscopy, mass spectrometry, FT-IR, and NMR and are optimized using DFT approach, which provided their theoretical framework. The stoichiometry between the ligand and the metal ions was also determined using Job's method. The thermogravimetric (TGA/DSC) analyses confirm the stability for all complexes at room temperature followed by thermal decomposition in different steps. DNA binding activities have been assessed by employing UV–visible and fluorescence spectra using the CT-DNA. The estimated intrinsic binding constant (Kb) for NiL, ZnL, and CdL complexes was 6.00 × 105, 5.58 × 105, and 4.7 × 105, respectively. In accordance with the Kb value, the quenching constant (Ksv) values of NiL, ZnL, and CdL are 5.59 × 105 M−1, 4.3 × 105 M−1, and 4.08 × 105 M−1 respectively. The anticancer properties have been assessed using MTT Assay. It has been found that the Ni(II) complex (NiL) is the most potent among the series with IC50 of 169 µg/mL. An in-vitro antioxidant experiment using DPPH was used to evaluate the synthesizedcomplexes' ability to scavenge free radicals. The findings indicated that the complexes exhibited notable antioxidant properties. The antioxidant property ZnL has been found to be the highest with an IC50 of 2.91 µg/mL and it follows the order is ZnL > NiL > CdL > L. Using the egg albumin denaturation technique, the anti-inflammatory property have been assessed, and the amount of protein denaturation inhibition has been computed. NiL has the highest % inhibition among the series studied. Comparatively, the metal complexes have been reported to exhibit higher biological activities than the prepared Schiff base ligand. The reason for the excellent biological properties observed in the metal complexes could be attributed to the incorporation of the electron-withdrawing CH3COO– during complexation. Molecular docking studies have been performed on the 2GYT protein and it has been found that the complexes have excellent binding affinity, with NiL having the lowest binding energy of −6.93 Kcal mol−1. The values suggested that NiL is more effective against HePG2 cancer cells, which is also in accordance with the MTT Assay results.

A Dinuclear Copper(II) Complex Electrochemically Obtained via the Endogenous Hydroxylation of a Carbamate Schiff Base Ligand: Synthesis, Structure and Catalase Activity.

In the present work, we report a neutral dinuclear copper(II) complex, [Cu2(L1)(OH)], derived from a new [N,O] donor Schiff base ligand L1 that was formed after the endogenous hydroxylation of an initial carbamate Schiff base H2L coordinated with copper ions in an electrochemical cell. The copper(II) complex has been fully characterized using different techniques, including X-ray diffraction. Direct current (DC) magnetic susceptibility measurements were also performed at variable temperatures, showing evidence of antiferromagnetic behavior. Its catalase-like activity was also tested, demonstrating that this activity is affected by temperature.

Exploring Bismuth (III) Sulpha Drugs Schiff Base Coordination Complexes: Design, Synthesis, Structural, Spectroscopic Characterization, and Biological Evaluations

The present study aimed to prepare and then evaluate the tetra and coordinated Bismuth (III) complexes [BiCl2 (L)] (LH = N, O donor Schiff base employed by the condensation of 1-acetyl-2-naphthol and 2-acetyl-1-naphthol using sulpha drugs as ligand) were derived by the reaction of bismuth (III) trichloride and sodium salt of an N, O donor Schiff base ligand and characterized. The authenticity of all the synthesized ligands and their Bi (III) complexes had been identified by microanalysis, various spectroscopic techniques like FT-IR, 1H NMR, and elemental analysis. The spectral evidence of the complexes has revealed the bidentate complexing nature of the Schiff base through phenolic oxygen and azomethine nitrogen atoms. The Schiff base ligand and Bismuth (III) complexes were assessed for antimicrobial activity. Assessment of antimicrobial activity against Gram-negative & Gram-positive bacteria and fungi has demonstrated that the complex (III) was more active than the Schiff base.

Formation of H-bonding networks in the solid state structure of a trinuclear cobalt(iii/ii/iii) complex with N2O2 donor Schiff base ligand and glutaric acid as bridging co-ligand: synthesis, structure and DFT study.

A trinuclear linear mixed-valence centrosymmetric cobalt(iii)-cobalt(ii)-cobalt(iii) complex, [CoII{(μ-L)(μ-Hglu)CoIII(OH2)}2](ClO4)2·6H2O has been synthesized during tetradentate N2O2 donor 'Schiff base' ligand, H2L {N,N'-bis(salicylidene)-1,3-diaminopropane} and glutaric acid (H2glu) as anionic co-ligand. The complex has been characterized by spectroscopic measurements and its solid state structure has been determined by single crystal X-ray diffraction analysis. The supra-molecular assembly formed by the hydrogen bonding interactions in the solid state of the complex has been analysed using DFT calculations.

Chemical fixation of atmospheric CO2 in tricopper(II)-carbonato complexes with tetradentate N-donor ligands: reactive intermediates, probable mechanisms, and catalytic and magneto-structural studies.

In the present era, the fixation of atmospheric CO2 is of significant importance and plays a crucial role in maintaining the balance of carbon and energy flow within ecosystems. Generally, CO2 fixation is carried out by autotrophic organisms; however, the scientific community has paid substantial attention to execute this process in laboratory. In this report, we synthesized two carbonato-bridged trinuclear copper(II) complexes, [Cu3(L1)3(μ3-CO3)](ClO4)3 (1) and [Cu3(L2)3(μ3-CO3)](ClO4)3 (2) via atmospheric fixation of CO2 starting with Cu(ClO4)2·6H2O and easily accessible pyridine/pyrazine-based N4 donor Schiff base ligands L1 and L2, respectively. Under very similar reaction conditions, the ligand framework embedded with the phenolate moiety (HL3) fails to do so because of the reduction of the Lewis acidity of the metal center, inhibiting the formation of a reactive hydroxide bound copper(II) species, which is required for the fixation of atmospheric CO2. X-ray crystal structures display that carbonate-oxygen atoms bridge three copper(II) centers in μ3syn-anti disposition in 1 and 2, whereas [Cu(HL3)(ClO4)] (3) is a mononuclear complex. Interestingly, we also isolated an important intermediate of atmospheric CO2 fixation and structurally characterized it as an anti-anti μ2 carbonato-bridged dinuclear copper(II) complex, [Cu2(L2)2(μ2-CO3)](ClO4)2·MeOH (2-I), providing an in-depth understanding of CO2 fixation in these systems. Variable temperature magnetic susceptibility measurement suggests ferromagnetic interactions between the metal centers in both 1 and 2, and the results have been further supported by DFT calculations. The catalytic efficiency of our synthesized complexes 1-3 was checked by means of catechol oxidase and phenoxazinone synthase-like activities. While complexes 1 and 2 showed oxidase-like activity for aerobic oxidation of o-aminophenol and 3,5-di-tert-butylcatechol, complex 3 was found to be feebly active. ESI mass spectrometry revealed that the oxidation reaction proceeds through the formation of complex-substrate intermediations and was further substantiated by DFT calculations. Moreover, active catalysts 1 and 2 were effectively utilized for the base-free oxidation of benzylic alcohols in the presence of air as a green and sustainable oxidant and catalytic amount of TEMPO in acetonitrile. Various substituted benzylic alcohols smoothly converted to their corresponding aldehydes under very mild conditions and ambient temperature. The present catalytic protocol showcases its environmental sustainability by producing minimal waste.

THE FIRST STRUCTURAL CHARACTERIZATION OF A NI(NCS)64– BRIDGED HOMOMETALLIC NI(II) CHAIN DERIVED FROM A N3O DONOR SCHIFF BASE LIGAND

Thiocyanate bridged homometallic Ni(II) chains have potential applications in areas such as molecular magnetism and spintronics due to their tunable magnetic properties. The magnetic properties of these chains are of particular interest and can lead to intriguing magnetic behaviors, such as antiferromagnetic or ferromagnetic interactions. In this context, we have successfully synthesized a Ni(NCS)64– bridge Ni(II) chain complex [Ni2(H2L)2(m1,3-NCS)2(NCS)4]n∙2nCH3CN (1), derived from a tetradentate N3O donor Schiff base ligand (HL). It has been thoroughly characterized by the help of elemental analysis and IR spectroscopy. Single crystal X-ray crystallography has confirmed the geometry of the chain complexes. Both Ni1 and Ni2 centers exhibit hexa-coordination with slightly distorted octahedral geometries, and their coordination environments differ significantly (NiN2O2S2 for Ni1 and NiN6 for Ni2). Within the solid-state structure of the complex, a noteworthy two-dimensional network of hydrogen bonding is observed. The present complex showing a unique example in the realm of single thiocyanato-bridged Ni(II) chains.

Metal–organic supramolecular architecture of oxo-bridged molybdenum(VI) complexes: Synthesis, structural elucidation and Hirshfeld surface analysis

New Binuclear monooxo, Mo2O4L21(H2O)CHCl3 (1), tetranuclear tetraoxo, Mo4O8L41 (2) and binuclear dioxo, Mo2O4L22 (3) bridged molybdenum(VI) complexes have been synthesized using two diprotic tridentate ONS donor Schiff base ligands H2L1 and H2L2 (H2L1 = S-benzyl-β-N-(2-hydroxyphenyl) methylene dithiocarbazate and H2L2 = S-benzyl-β-N-(5‑bromo-2-hydroxyphenyl) methylene dithiocarbazate. All the three complexes have been characterized by elemental analyses and IR, UV–vis and 1H NMR spectroscopies and their crystal structures were solved by single crystal X-ray diffraction technique. Complexes (1) and (3) crystallized in triclinic space group P-1 and complex (2) in monoclinic space group P21/n. Complexes 1, 2 and 3 exhibit distorted octahedral geometry around Mo(VI) center. X-ray crystallography reveals that in the crystal packing of the complexes C–H···O, O–H···O, O–H···N, C–X···π (X = Br) and π···π stacking interactions cooperatively take part. A detailed analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions which are crucial in building different supramolecular architectures of three molybdenum complexes. Crystal structure analysis supported with the Hirshfeld surface and fingerprint plots enabled the identification of the significant intermolecular interactions. The intermolecular interactions are further characterized by analyzing the topological parameters through Bader's theory of ‘atoms in molecule’ (QTAIM) along with the ‘non-covalent interaction’ (NCI) plot index. The investigation of topological parameters of electron density at the (3, −1) bond critical point classified the interactions as ‘closed-shell’ interactions.

In Vitro Insight on Antifungal-Specific Potentiality of Ni(II) Complex against Colletotrichum siamense and Fusarium equisetum Phytopathogens.

In an initiation to investigate a prospective bioactive compound, a mononuclear Ni(II) complex with N, N, and O donor Schiff base ligand was synthesized and characterized in the present study through FTIR, ESI-mass, and X-ray crystallographic diffraction studies. A slightly distorted octahedral geometry has been obtained for the Ni(II) complex from X-ray crystallographic diffraction studies. In vitro comprehensive biological studies show the antifungal specific efficiency of the complex against Colletotrichum siamense (AP1) and Fusarium equisetum (F.E.) pathogens, which are responsible for anthracnose and wilt disease, respectively, but no inhibitory effect on both Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) for these pathogens was observed to be 0.25 and 0.5 mM, respectively. The experiment also reveals that significant damage of mycelia and enlarged, misshaped damaged spores are noticed in comparison to hexaconazole, used as a positive control under a light microscope post 48 h treatment of AP1 and F.E. with the MIC of the complex. The binding interaction studies of the complex with DNA and BSA performed through a variety of spectroscopic techniques demonstrate a strong binding behavior of the complex for both the binding systems. The observed negative ΔH° and ΔS° values for DNA reveal the existence of hydrogen-bonding/van der Waals interactions for DNA which was also exemplified from the molecular docking and self-assembly studies of the complex. The positive ΔH° and ΔS° values for BSA demonstrate the hydrophobic interactions of the complex with BSA. However, cytotoxicity studies against the MDA-MB-231 breast cancer cell line did not demonstrate any significant potentiality of the complex as an anticancer agent. All the bio-experimental studies provide clear evidence that the synthesized Ni(II) complex exhibits potential antifungal activity and could be used as a therapeutic fungicide agent in comparison to hexaconazole in agricultural practices.

New thiosemicarbazones and their palladium(II) complexes: Synthesis, spectroscopic characterization, X-ray structure and anticancer evaluation

Thiosemicarbazones (TSCs) have proven to be an important group of NS donor Schiff base ligands. Their biological activities, structural and donor diversities are often improved after coordination to a metal ion. In this work, novel thiophene-based thiosemicarbazone ligands; (E)-N,N’-dimethyl-2-((5′-methyl-[2,2′-bithiophen]-5-yl)methylene)hydrazine-1-carbothioamide (L1), (E)-N-ethyl-2-((5-phenylthiophen-2-yl)methylene)hydrazine-1-carbothioamide (L2) and (E)-2-((5′methyl)-[2,2′-bithiophen]-5-yl)methylene)-N-phenylhydrazine-1-carbothioamide (L3) were synthesized via condensation reaction. The corresponding complexes (C1, C2 and C3) were synthesized by reacting the ligands with Pd(cod)Cl2 under inert nitrogen environment. All the prepared ligands and complexes were characterized by using the FTIR, UV–Vis, 1H and 13C NMR, elemental analysis and single crystal X-ray crystallography on ligand L2. The anticancer activities of the complexes were investigated against human the Caco-2, HT-29, HeLa and non-cancerous KMST-6 cell lines. In the preliminary studies, unexpectedly of all ligands and complexes, L1 showed the best anti-tumor activities at 100 µg/mL with cell viabilities < 31% in all the cell lines. In general, cell lines were more susceptible to complexes than free ligands except for C1. Complex C2 had the highest activity among complexes; HeLa (8.4%), HT-29 (8.8%), Caco-2 (16.1%) and KMST-6 (24.5%) cell viabilities at a concentration of 100 µg/mL. The C3 complex demonstrated appreciable selectivity since it had minimal effect on non-cancerous KMST-6 cell line (76%) with relatively reduced cytotoxicity in other cells except in HeLa (0.0%). All the complexes prepared inhibited proliferation of HeLa cells.

New tetradentate long chain Schiff base and its cadmium(II) complexes: Antimicrobial, antioxidant and anticancer activities

In the current study, a new long chain tetra-nitrogen donor Schiff base ligand (SB) entitled as N1,N2-bis(2-(((1E,2E)-3-(4-(dimethylamino)phenyl)allylidene)amino)ethyl)ethane-1,2-diamine and some its molecular cadmium (II) complexes formulated as Cd(SB)X2 (X = halide/pseudohalide) were prepared and characterized by various physicochemical and spectral methods such as melting point, micro-analytical data, thermal analysis (TG/DTG/DTA), molar conductivity and UV–Visible, FT-IR, 1H, and 13C NMR spectroscopies. Also nanostructured cadmium chloride and iodide chelate complexes approved by PXRD SEM and EDX techniques were synthesized to use as precursor to prepare nanostructure cadmium oxide. The particle sizes about 2–10 nm were estimated for nanostructured cadmium complexes and oxide. Thermo-gravimetric plots showed the compounds are decomposed via 2–4 steps with weight loss of 69–100% to leave out metallic Cd or cadmium salt as final residue. Thermo-kinetic activation parameters calculated based on TG plots suggested non-spontaneous thermal decomposition with activation Ea*, ΔH* and ΔG* parameters in the ranges of (13.54–160.48 kJ.mol−1), (8.22–155.95 kJ.mol−1) and (1.59 × 102-4.1 × 102 kJ.mol−1) respectively. Moreover, the pharmacological activities of the compounds were investigated against some pathogenic fungi and bacteria. According to screening data, the SB ligand showed lower antimicrobial activities than its complexes toward selected microbes so that the cadmium(II) nitrate, thiocyanate and azide were found the most active against B. subtilis, S. aureus, P. aeruginosa and E. coli respectively. The evaluation of DNA cleavage potency using the agarose gel electrophoresis technique suggested Cd(SB)Cl2 as the most destructive compound. Furthermore, the antioxidant assessment of the compounds as compared with the standard references by DPPH and FRAP methods proposed Cd(SB)Cl2 and Cd(SB)Br2 as the best antioxidant. In final, the cytotoxicity of the synthesized compounds was appraised toward human breast cancer (MCF-7) and prostate cancer (PC3) cell lines employing MTT and nitric oxide level assays. The results suggested Cd(SB)Br2 as more cytotoxic than other complexes against two studied cancer cell lines.

Evaluating the in vitro antidiabetic, antibacterial and antioxidant properties of copper(II) Schiff base complexes: An experimental and computational studies

In recent years, metal-based compounds have been explored as potential remedies for majorhealth issues such as diabetes, bacterial infections, and oxidative stress, which impact the general well-being of humans globally. Diabetes, bacterial infections, and oxidative stress are major health concerns affecting millions worldwide. Researchers have been exploring the use of metal-based compounds as potential treatments for these conditions. In our quest towards identifying biologically viable metal-based compounds, three novel Cu(II) complexes were synthesized from halogen-substituted ON donor Schiff base ligands. These ligands were obtained by condensing 2-hydroxybenzldehyde with three different halogen-substituted anilines. The ligands and their complexes were characterized using various spectroscopic techniques such as 1H and 13C nuclear magnetic resonance, Fourier Transform-Infrared, Ultraviolet–visible spectra, elemental analysis, mass spectrometry, and single-crystal X-ray spectroscopy to elucidate their structures. The compounds were screenedfor antidiabetic (α-glucose and α-amylase enzymes inhibition assay), antioxidant (2,2-diphenyl-1-picrylhydrazyl(DPPH), ferric reducing antioxidant potential (FRAP) assay, and nitric oxide(NO) radical scavenging), and antimicrobial activities. The pharmacological activity revealed that the efficacy of the ligands was enhanced upon coordination, and CuL3 is more potent among the complexes, having higher inhibition activity on α-glucosidase (IC50 = 100.1 μM) than the control, whose IC50 is 112.4 μM on the same enzyme. For radical scavenging activity, the results showed that the complexes have higher scavenging activity on DPPH radicals than their ligands and the control. For the FRAP assay, the complexes show higher activity than their ligands. Similarly, NO radical scavenging activity results indicate the ligands have higher activity than their complexes, while the complexes outperformed the control at all concentrations tested. The In vitro antibacterial results on some selected Gram-positive and Gram-negative bacteria revealed the complexes have higher antibacterial activity than their corresponding ligands, with CuL3 taking the lead, showing a MIC value of 4 g/mL on some of the bacteria tested. Also, density functional theory calculations at different levels of DFT and basis sets were used to investigate the optimized geometry, electronic structure (energy of HOMO and LUMO, Mulliken atomic charge, dipole moment, hardness, and softness, electrophilicity, and spectral properties) of the synthesized compounds. Molecular docking studies were carried out to investigate the binding affinity of the receptor proteins to other proteins and to establish the mechanism of action at the active sites.

Synthesis, crystal structure, theoretical studies and biological evaluation of nickel(II) complex derived from N2O2 tetradentate Schiff base

In the present study we report the synthesis, characterization, biological studies of the N2O2 donor Schiff base ligand: N,N'-bis(2-hydroxypropiophenone)-1,2-ethanediamine L and its’ nickel(II) complex NiL. We used 1H and 13C NMR, FT-IR, Raman and UV–Vis spectroscopy for characterization, and the structure of the complex was determined by single crystal X-Ray crystallography. Hirshfeld surface analysis and two-dimensional fingerprint plots and energy frameworks of NiL were calculated to quantify the interatomic interactions present in the crystal. The evaluation of antioxidant capacities of the prepared compounds were realized by two different in vitro methods (DPPH; ABTS) and showed an average inhibition. The biological activity was predicted for nikel complex (NiL) using the PASS software. On the other hand, the structural, optical properties, static and dynamic hyperpolarizabilities of NiL, PdL and PtL are studied using DFT and TD-DFT methods. The results show that the geometry parameters and the simulated UV/Vis absorption spectra of the NiL are in excellent agreement with the experiment. Furthermore, the results obtained showed that ML (M = Ni, Pd and Pt) exhibits a high hyperpolarizability (at static and dynamic regime) and thus, becomes a promising candidate for second-order NLO materials.