Schiff Base Ligand Research Articles

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.

Characterization and Cytotoxicity Assessment of Synthesized Palladium (II) Complex-Encapsulated Zinc Oxide Nanoparticles for Cancer Treatment.

The treatment of cancer often leads to a range of adverse effects. Encapsulating drugs can mitigate these effects and enhance drug efficacy by enabling a controlled release at the site of interest. This study details the successful synthesis of zinc oxide nanoparticles (ZnONPs) through the precipitation of Zn(NO3)2·6H2O with KOH. A Pd(II) complex drug was synthesized from a Schiff base ligand derived from 2-hydroxybenzohydrazide and (E)-1-(2-(p-tolyl)hydrazono)propan-2-one using potassium tetrachloropalladate(II). This complex was subsequently incorporated into ZnONPs. Characterization of the resulting compounds was performed using Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS), Zeta Potential, Fourier Transform Infrared (FTIR) Spectroscopy, and UV-visible spectroscopy. TEM imaging revealed particle sizes of 160.69 ± 4.74 nm for ZnONPs and 185.28 ± 2.3 nm for the Pd(II) complex-encapsulated ZnONPs. The Zeta potential values were 6.53 mV for ZnONPs and 7.36 mV for Pd(II) complex-encapsulated ZnONPs. UV-visible spectroscopy showed an absorption peak at 360 nm for ZnONPs, while the Pd(II) complex-encapsulated ZnONPs exhibited a peak at 410 nm. FTIR analysis indicated the presence of the Pd(II) complex within the ZnONPs, as evidenced by a consistent Zn-O vibrational band at 832 cm-1 and a shift in another peak from 460 to 413 cm-1. Additionally, the detection of a C = N stretching vibration at 1548 cm-1 and a carbonyl stretch at 1626 cm-1 was observed. The Encapsulation Efficiency (E.E.) of the Pd(II) complex was 97.2%. A drug release experiment conducted at pH 7 showed a steady-state release pattern after 16 h, with a cumulative release of 44.3%. The cytotoxic effects of the Pd(II) complex and its encapsulated form in ZnONPs on the MCF-7 cell line were assessed via MTT test. The Pd(II) complex encapsulated within ZnONPs exhibited decreased toxicity relative to the unencapsulated drug, as evidenced by a higher IC50 value of 418.5 μg/ml. This suggests that the encapsulation facilitates a sustained release, which allows for targeted accumulation within cells. The elevated IC50 value indicates that the drug delivery system may be engineered to modulate the release of the drug in a more controlled manner, potentially resulting in a prolonged release profile rather than an immediate therapeutic impact.

Studies of the nonlinear optical properties of a synthesized Schiff base ligand using visible cw laser beams

The synthesized Schiff base ligand (compound Z1) is analyzed by IR, mass, 1HNMR, and 13CNMR spectroscopies. Computational chemical modeling is performed to examine the geometry optimization and molecular structure of compound Z1 by using the DFT/ WB97XD/6-31+G(d,p) method. The parameters HOMO–LUMO energies with nonlinear optical (NLO) properties are computed. The results indicate good agreement between experimental and theoretical data, so that compound Z1 to have good NLO properties. The NLO properties of the compound Z1 are examined under excitation with a 473 nm, cw, low power laser beam via two techniques, viz., diffraction patterns (DPs) and the standard Z-scan techniques. As high as 3.03 × 10−11 m2 W−1 of the compound Z1 of the nonlinear refractive index (NLRI), n2, is obtained via the DPs. Both static and dynamic all –optical switching (SAOS and DAOS) are tested using 473 nm and 532 nm cw low power laser beams.

Synthesis of chiral Cu(II) complexes from pro-chiral Schiff base ligand and investigation of their catalytic activity in the asymmetric synthesis of 1,2,3-triazoles

A pro-chiral Schiff base ligand (HL) was synthesized by the reaction of 2-amino-2-ethyl-1,3-propanediol and pyridine-2-carbaldehyde in methanol. The reaction of HL with CuCl2·2H2O and CuBr2 in methanol gave neutral mononuclear Cu(II) complexes with general formula of [Cu(HL)Cl2] (1) and [Cu(HL)Br2] (2), respectively. By slow evaporation of the methanolic solutions of 1 and 2, their enantiomers were isolated in crystalline format. The formation of pure chiral crystals in the racemic mixture was amply authenticated by single crystal X-ray analysis, which indicated that S-[Cu(HL)Cl2], R-[Cu(HL)Cl2], and S-[Cu(HL)Br2] are crystallized in chiral P212121 space group of orthorhombic system. Preferential crystallization was used to isolate the R and S enantiomers as single crystals and the isolated compounds were also studied by CD analysis. Structural studies indicated that the origin of the chirality in these compounds is related to the coordination mode of the employed pro-chiral ligand (HL) because one of its carbon atoms has been converted to a chiral center in the synthesized complexes. Subsequently, these complexes were used in click synthesis of a β-hydroxy-1,2,3-triazole and the results of catalytic studies indicated that 1 and 2 can act as enantioselective catalysts for the asymmetric synthesis of β-hydroxy-1,2,3-triazole product under mild condition. This study illustrates the significant capacity of the use of pro-chiral ligands in preparing chiral catalysts based on complexes which can also be considered as an effective approach to cheap chiral catalysts from achiral reagents.

Photophysical Studies of a Zr(IV) Complex with Two Pyrrolide-Based Tetradentate Schiff Base Ligands.

The reaction of two equivalents of N,N'-bis(2-pyrrolylmethylidene)-1,2-phenylenediamine (H2bppda) with tetrabenzylzirconium provided the air- and moisture-stable eight-coordinate complex Zr(bppda)2. Temperature-dependent steady-state and time-resolved emission spectroscopy established weak photoluminescence (ΦPL = 0.4% at 293 K) by a combination of prompt fluorescence and thermally activated delayed fluorescence (TADF) upon visible light excitation at and around room temperature. TADF emission is strongly quenched by 3O2 and shows highly temperature-sensitive emission lifetimes of hundreds of microseconds. The lifetime of the lowest energy singlet excited state, S1, was established by transient absorption spectroscopy and shows rapid deactivation (τ = 142 ps) by prompt fluorescence and intersystem crossing to the triplet state, T1. Time-dependent density functional theory (TD-DFT) calculations predict moderate ligand-to-metal charge transfer (LMCT) contributions of 25-30% for the S1 and T1 states. A comparison of Zr(bppda)2 to related zirconium pyridine dipyrrolide complexes, Zr(PDP)2, revealed important electronic structure changes due to the eight-coordinate ligand environment in Zr(bppda)2, which were correlated to differences in the photophysical properties between the two compound classes.

Infrared spectral features of the charge carriers in nickel salen polymeric complexes

A series of the polymeric complexes (PCs) of nickel(II) with N2O2 Schiff base ligands have been studied by in situ Fourier Transform Infrared (FTIR) spectroelectrochemistry. The molecular structure of the metal-salen complexes as starting materials for the polymer synthesis was modulated by various substituents in the phenolate moieties and diimine bridge. Two groups of the infrared-active vibration (IRAV) bands are obtained in the spectra depending on the oxidation level of the polymers. The assignment of the main IRAV bands was carried out and the electrochemically generated charge carriers were determined. Analysis of the spectroscopic features observed in the mid and near IR region provides information on the charge distribution within the polymer film.

Synthesis and Characterization of Novel Schiff Base Complexes of Cu (II), Cd (II), Ni (II), and Co (II) Ions with N'-(4-Nitrobenzylidene) Isonicotinohydrazide

The Schiff base complexes of Cu (II), Cd (II), Ni (II), and Co (II) ions were synthesized utilizing Schiff base ligand. The Schiff base ligand was produced through the reaction of isoniazid with equimolar quantities of p-nitrobenzaldehyde yielding final product of N'-(4-nitrobenzylidene) isonicotinohydrazide (L). The ligand and its metal complexes were assessed by TLC, melting point determination, conductivity measurement, FTIR spectroscopy, magnetic moment analysis, and UV-Vis spectroscopy. The FTIR spectra revealed that the Schiff base ligand established coordination bonds with the metal ion by utilizing the nitrogen (N) atom of the azomethine group and the oxygen (O) atom of the carbonyl group. All synthesized compounds exhibited cytotoxicity against brine shrimp nauplii, thereby confirming their biological activity. [Ni(L)2] and [Cd(L)2] complexes displayed greater cytotoxic or anticancer efficacy. In addition, the antibacterial efficacy of both ligand and its complexes was investigated against several harmful bacteria. In comparison with the ligand (L), the antibacterial activity of the complexes of [Cu(L)2], [Cd(L)2], and [Ni(L)2] is higher, whereas that of [Co(L)2] is lower.

Synthesis of novel bi-Zwitterion Schiff base derivate from 4‑hydroxy-2H-pyran-2-one: DFT/HSA-interactions, thermal, physicochemical, TD-DFT and optical activity

A novel tetradentate bi-Zwitterion Schiff base (SB): 3,3′-((1E,1′E)((oxybis(4,1-phenylene))-bis-(azanylylidene))-bis(ethan-1-yl-1-ylidene))bis(4‑hydroxy-2H-pyran-2-one) was synthesized, via reflux condensation of 3-acetyl-4‑hydroxy-6-methyl-2H-pyran-2-one with 4,4′-oxydianiline in methanol. The SB ligand was characterized using various physicochemical techniques, including 1HNMR , elemental analysis (CHN-EA), XRD, MS, UV–vis, and FT-IR. The XRD analysis confirmed the presence of a bi-zwitterionic salt form, characterized by intra-H-bond interactions between [N+—H…−O] groups. Hirschfield surface analysis (HSA) and MEP/MAC/NPA were conducted to gain insight into the intra/intermolecular hydrogen bond interactions of the molecule. The completion of the SB dehydration reaction was UV–vis., tracked by studying the behavior of the reactants before and after mixing. Additionally, the absorbance/transmittance, TD-DFT, and optical properties of the SB were evaluated. Finally, the TG/DTG analysis was used to determine the thermal stability of the desired SB ligand.

Gadolinium Schiff-base complex on nanocomposite of graphene oxide magnetic nanoparticles as a robust, reusable and chemoselective nanocatalyst in the C–C coupling reactions

Graphene is an important phase of carbon, which is easily available and oxidable to graphene oxide with a variety of applications. Therefore in this work, graphene oxide (GO) was synthesized, and further it was magnetized by nickel magnetic nanoparticles. The surface of graphene oxide magnetic nanoparticles (Ni-GO MNPs) was modified with (3-aminopropyl)triethoxysilane (APTES). On the other hand, (3,4-bis(−(2-hydroxybenzylidene)amino)phenyl)(phenyl)methanone Schiff-base ligand (bis(HBAPM)) was synthesized using condensation of salicylaldehyde and 3,4-diaminobenzophenone. In the next step, bis(HBAPM) was immobilized on the surface of modified Ni-GO MNPs toward synthesis of immobilized Schiff-base on Ni-GO MNPs (bis(HBAPM)@Ni-GO MNPs) as a heterogeneous Schiff-base ligand. In the final step, the gadolinium catalyst was stabilized on its surface (Gd-bis(HBAPM)@Ni-GO MNPs) as a robust, reusable, efficient, chemoselective, and novel nanocatalyst. Gd-bis(HBAPM)@Ni-GO MNPs were characterized by nitrogen adsorption/desorption, FT-IR, SEM imaging, EDS analysis, WDX analysis, XRD, and VSM analysis. After the characterization of Gd-bis(HBAPM)@Ni-GO MNPs, its catalytic performance was employed as a highly practical, retrievable, stable, and hybrid organic–inorganic catalyst in the carbon–carbon coupling of the Suzuki reaction. Due to the recoverability and heterogeneous nature of Gd-bis(HBAPM)@Ni-GO MNPs, it can recycled again for 5 runs.

Square-planar nickel/copper(II) complexes of (E)-2-(((2-ethylphenyl)imino) (phenyl) methyl)phenol: Supramolecular analysis, keto-enol tautomerism, polymorphism and antibacterial activities

A new Schiff base proligand, (E)-2-(((2-ethylphenyl)imino)(phenyl)methyl)phenol (HL), was synthesized from 2-hydroxybenzophenone and 2-ethylaniline and its coordination chemistry with nickel(II) and copper(II) acetate explored. In solution, the proligand HL undergoes ketoimine -enolimine tautomerism which settles exclusively into an enolimine form in the solid-state. Interestingly, while a single crystalline habit was obtained for the nickel complex 1 (block-shaped single crystals), the copper species 2 was found to solidify in two detectable polymorphs: block-shaped crystals (2a, monoclinic space group P21/c) and rhombic crystals (2b, triclinic space group P-1). Single-crystal X-ray diffraction studies reveal that the N,O Schiff base ligand chelates the divalent metal ions with square-planar geometry in the isostructural 1 and 2a and in a distorted square-planar geometry with a dihedral chelate-plane angle of 27.9° in 2b. The copper complex 2 exhibits significant antibacterial activity against the E. coli and medium activity against S. aureus bacteria. The physical properties of the complexes were further probed using thermal techniques, while their electronic structure was investigated by electrochemistry and electronic absorption spectroscopy.

Antiferromagnetic resorcinol bridged dinuclear square-planar copper (II) complexes: Syntheses, structural, spectroscopic and magnetic properties

A new C2-symmetric Schiff base ligand (H2L) featuring a core resorcinol bridging unit has been created, utilizing the Duff formylation reaction followed by the Schiff base condensation reaction. The ligand was characterized by various spectroscopic techniques.. Cu(II) salts with varying coordinating anions (Cl− and SCN−) in methanol were allowed to react with this ligand in a 2:1 M ratio to create dinuclear Cu(II) complexes. The complexes were isolated in pure form and characterized by, elemental analysis,single crystal X-ray crystallography and various spectroscopic techniques. X-ray analysis discloses that both complexes are dinuclear, where the ligand (H2L) being tridentate in nature, coordinates to Cu(II) through its two N donor atoms and one O donor atom in the equatorial positions. The respective anions (−Cl− for 1 and –SCN− for 2) coordinate to Cu(II) to complete its square planar geometry. Temperature dependent magnetic susceptibility measurements indicate weak antiferromagnetic exchange interactions with a coupling constant of J = −5.9(1) cm−1 and g = 2.148(1) for 1 and J = −10.08(1) cm−1 and g = 2.106(1) for 2.

Aminoquinoline-Based Ruthenium(II) and Iridium(III) Polypyridyl Complexes: Investigating Potential Photosensitisers for Cancer Treatment via Photodynamic Therapy

Cancer is a devastating noncommunicable disease that remains one of the most pressing health challenges of the twenty-first century. Chemotherapy stands as one of the most common and effective cancer treatment methods. However, severe side effects and acquired drug resistance in many cancers have significantly diminished the efficacy of current chemotherapeutic agents. The urgent demand for novel treatment modalities has led to the development of photodynamic therapy (PDT) for the treatment of various cancer types. In this work, the synthesis of aminoquinoline-based transition metal complexes containing two PGMs (Ir(III) and Ru(II)) as potential photosensitisers is described. Mononuclear N,N-chelated Ru(II) and Ir(III) transition metal complexes were synthesized by reacting 4-aminoquinoline Schiff base ligands, which contained either a pyridyl or a quinolyl entity. The photostable Ru(II) and Ir(III) polypyridyl complexes were investigated for their potential use as PDT agents. In vitro cytotoxicity screenings conducted against a melanoma cell line (501mel) both in the absence and presence of light confirmed that all complexes demonstrated increased biological activity when exposed to visible light at 455 nm. Overall, the complexes containing a quinoline substituent consistently demonstrated superior activity compared to those substituted with pyridine, underscoring the significance of the quinoline pharmacophore for anticancer drug design.

Organoruthenium metallocycle induced mutation in gld-1 tumor suppression gene in JK1466 strain and appreciable lifespan expansion

Four Ru(II) complexes (A2-A5) were synthesized from the reaction of coumarin Schiff base ligands (7da2-tsc, 7da3-mtsc, 7da4-etsc and 7da5-ptsc) with [RuHCl(CO)(PPh3)3]. The compounds were characterized by FT-IR, UV–Vis, 1H, 13C and 31P NMR, mass spectrometry and crystallographic analysis. Calf Thymus DNA (CT-DNA) binding studies revealed the intercalative mode of binding of the complexes with DNA. The results of Bovine serum albumin (BSA) binding studies established the interaction between BSA followed static quenching mechanism. The cytotoxic effects of the complexes and the ligands were evaluated against breast (MCF-7 and MDA-MB-231) and lung carcinoma cell lines (A549 and NCI-H460) using MTT assay. Complex A4 demonstrated potent cytotoxic effects on both breast and lung cancer cells. Furthermore, morphological observations and FACS analysis showed the decrease in cell density by complex A4 by induced morphological changes and apoptotic body formation and cell death in both breast and lung cancer cells. Moreover, the invertebrate model Caenorhabditis elegans was employed to assess the in vivo anticancer activity of compound A4. The findings indicated that the treatment with A4 reduced tumor development and significantly extended organismal lifespan by 64 % in the tumoral strain JK1466 without adversely affecting essential physiological functions of the worm. Additionally, A4 demonstrated an upregulation of two crucial antioxidant defense genes. Overall, these results suggested that the compound A4 can be a potential candidate with novel chemotherapeutic applications.

Unveiling the Therapeutic Potential of Organotellurium(IV) Schiff Base Complexes through Structural Elucidation, Antimalarial, Antioxidant and Antimicrobial Studies

Infectious diseases have long been a formidable adversary to human health and well-being, presenting a persistent global challenge with far-reaching implication for individuals, communities and societies at large. Thus, with the aim of a combating agent against malarial and oxidant causing ailments, the newly synthesized Organotellurium(IV) complexes with a hydroxynaphthaldehyde Schiff base ligand are proposed in the present research. The structures of the complexes were established through various physical and spectral analysis. The weak electrolytic (8.77 to 35.08 ohm−1 cm2 mol−1) and crystalline nature of the compounds were demonstrated by molar conductivity and TGA, respectively. The ligand and complexes (7a-7f) shows molecular ion peaks at m/z 458.3563, 726.1039, 713.6978, 727.6179, 799.4780, 771.3178 and 799.3978 amu which were well consistent with their formula, revealing formation of compounds. The shifting of ligand's azomethine peak (7.74 ppm) and disappearance of naphthyl hydroxyl proton (12.28 ppm) in 1H NMR spectra confirmed the chelation of ligand with metal ion in proposed manner. In the FT-IR spectra, the complexation of ligand with metal ion was confirmed by disappearance of hydroxyl group (3355 cm−1) band and shifting of C=N (1245 cm−1) and C-O (1632 cm−1) band whereas appearance of Te-O (of 285-293 cm−1) and Te-N (458-467 cm−1) bands, revealed the bonding of metal with metal and octahedral nature of the complexes. Optimized structures, HOMO-LUMO energies and associated chemical reactivity descriptors of the compounds were computed by DFT calculations. The in vitro studies demonstrate that the complexes 7c (1.06 ± 0.11 μM) and 7f (1.22 ± 0.05 μM) exhibited moderate inhibition of the Plasmodium falciparum 3D7 strain, complexes 7a (100.96 ± 0.32 μg/mL) and 7d (96.32 ± 0.40 μg/mL) demonstrated the highest free radical quenching ability. Complex 7c displayed the highest antibacterial actions, whereas 7f exhibited the highest antifungal actions against the tested pathogens. Molecular docking and ADMET studies demonstrated enhanced binding affinity of the complexes compared to the Schiff base and their drug-like qualities.

Photo‐induced organo‐manganese‐mediated radical polymerization of acrylates under LED irradiation

The role of manganese in photo‐induced organometallic‐mediated radical polymerization (photo‐OMRP) under LED (light‐emitting diode) irradiation has not been previously explored. In this study, four manganese (II) complexes, namely [Mn(6‐tert‐butyl‐N,N′‐propanebis [salicylimine])] (Mn‐Bu), [Mn(6,3‐di‐tert‐butyl‐N,N′‐propanebis [salicylimine])] (Mn‐Bu2), [Mn(6‐ethoxy‐N,N′‐propanebis [salicylimine])] (Mn‐Ethoxy), and [Mn(6,3‐di‐ethoxy‐N,N′‐propanebis [salicylimine])] (Mn‐Ethoxy2), were synthesized using both symmetrical and non‐symmetrical tetradentate N2O2 Schiff base ligands. The Schiff base ligands were characterized by Fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis), and nuclear magnetic resonance spectroscopy (NMR). The Mn (II) complexes were characterized by FTIR, UV–Vis, elemental analysis, molar conductivity, cyclic voltammetry, MALDI‐TOF mass spectrometry, electron paramagnetic resonance, and rationalized with density functional theory (DFT) studies. All complexes were evaluated as photo‐OMRP mediators under LED irradiation at 390 nm and in the 400–800 nm range. The photopolymerization utilized methyl acrylate (MA) and diphenyl(2,4,6‐trimethylbenzoyl)phosphine oxide (TPO) in varying molar ratios of [MA]/[MnII]/[TPO] (900/1/1, 600/1/1, and 600/1/0.5). The photo‐OMRP of MA mediated by Mn‐Bu2 showed the best control over molecular weight (Mn matching Mn,th) and dispersity (Ð < 1.30) at a [MA]/[MnII]/[TPO] = 600/1/0.5 M ratio. The polymerization system demonstrated a living character, as evidenced by reversible “on/off” light source switching. Furthermore, a block copolymer of poly (methyl acrylate)‐b‐poly (butyl acrylate) was successfully synthesized employing a sequential visible‐light‐induced process, with the Mn‐Bu2 system showing the best results.

Novel Schiff Base Ligand and its Three Homotrinuclear Metal Complexes and their Bioactivity

 A new homotrinuclear metal complexes derived from N-isopentylidine ethylenedimine dithiocarbamate schiff base ligand have been synthesized and characterized using elemental analyses, molar conductivity, spectral (FT-IR and UV–Vis), magnetic susceptibility measurements and MM2 theoretical calculations. The results suggested that the complexes have the general formulae, {M3[(C2H5)2C= En-dtc]2(Cl)2(H2O)2}, where M= Co (II), Ni(II) and Cu(II). IR results suggest that the schiff base ligand acts in a tetradentate attachment. Antibacterial activity assays against Staphylococcus aureus (+) showed that both the dithiocarbamate ligand and schiff base complexes have good activity, while no antibacterial activity was observed against Escherichia coli (-). Keywords: New schiff base ligand; Homotrinuclear Complexes, Bioactivity. الملخص حضرت المعقدات الثلاثية النوى الجديدة للكوبلت (II) و النيكل (II) والنحاس (II) والمشتقة من ليجاند قاعدة شيف الجديدة N-ايزوبنتيلدين ايثلين ثنائي أمين ثنائي ثايوكارباميت و شخصت باستخدام طرق التحليل الدقيق للعناصر و قيم التوصيلية المولارية الكهربائية و أطياف الأشعة تحت الحمراء و الأطياف الإلكترونية و الحساسية المغناطيسية و استخدم برنامج MM2لحساب أطوال الروابط و الزوايا. النتائج تقترح الصيغة العامة للمعقدات {M3[(C2H5)2C=En-dtc)2Cl2(H2O)2]} حيث M= الكوبلت (II) أو النيكل (II) أو النحاس (II). تقترح أطياف الأشعة تحت الحمراء مخلب رباعي السن لليجاند قاعدة شيف. كما اظهرت اختبارات الفعالية البيولوجية النشاط الجيد لكلا من ليجاند ثنائي أمين ثنائي ثايوكارباميت و معقدات قاعدة شيف ضد البكتيريا الموجبة (+) للجرام (Staphylococcus aureus), في حين لم يلاحظ أي نشاط مضاد السالبة (-) للجرام (Escherichia coli).     

Design, synthesis, and characterization of M(II)-Schiff base complexes containing 3,5-di-tert-butyl salicylaldehyde: DNA binding/cleavage, DPPH radical scavenging activity, cytotoxic activity, and catalytic activity investigation

Two mononuclear Cu(II) and Zn(II) based complexes were synthesized via microwave-assisted method utilizing Schiff base ligand based on 3,5-di-tertbutylsalicylaldehyde. The compounds were characterized using elemental and spectroscopic analysis methods. The ligand posed as an ON-donor ligand, confirmed by spectrum analysis in the complexes. A geometry optimization analysis was also performed using density functional theory to obtain the geometry, stability, and electronic properties of the synthesized compounds. CuL1 has a distorted square planar geometry, whereas ZnL1 has a distorted tetrahedral geometry. Fluorescence and absorbance spectroscopy were utilized to explore the interaction properties of calf thymus-deoxyribonucleic acid (CT-DNA) with the complexes. The CuL1 and ZnL1 are highly sensitive to DNA binding, with binding constant (Kb) in the range of 105 M−1, representing substantial interaction with CT-DNA, combining intercalation and electrostatic interactions. The Stern-Volmer constant (Ksv) obtained from the fluorescence spectroscopy method varied from 3.31 x 104 to 8.42 x 104 M−1, indicating moderate DNA binding. Circular dichroism spectroscopy confirmed the presence of intercalative binding among the DNA and the complexes. The in-vitro DNA cleavage activity revealed that complexes could efficiently break the supercoiled plasmid DNA without using any external agents. The complex CuL1 induced significant cytotoxicity for Dalton’s lymphoma cancer cell lines, having IC50 values of 18.96 ± 0.021 μM. The antioxidant activity of the compounds was also studied, confirming CuL1 to be the most active antioxidant with IC50 = 399.27 µM. A molecular docking simulation was also conducted to comprehend the compounds' interaction mechanism with CT-DNA (1BNA) and cancer cells (BCL-family proteins). Furthermore, the catalytic activity of the zinc metal complex was assessed for multi-component reactions involving substituted benzaldehydes, malononitrile, and resorcinol.

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.

Copper-zinc metal complex exhibiting bactericidal and antibiofilm activity by membrane damage and quorum sensing inhibition

A hetero di nuclear complex [Zn(o-phen)LCu(OAc)] (K3 compound), where, H3L = o-HOC6H4C(H)=N−NH−C(OH)=N−NC(H)−C6H4OH-o, o-phen = 1,10-phenanthroline, and OAc = CH3COO− was synthesized. The Schiff base ligand in its keto form used for synthesis was derived from the condensation of salicylaldehyde and carbohydrazide, however, the Schiff base was found to coordinate in its enol form (L3−) as it was confirmed from the reported crystal structure of K3 compound. The K3 compound displayed significant antibacterial activity in both planktonic and biofilms of the test organisms, Pseudomonas aeruginosa and Staphylococcus aureus. The anti-quorum sensing activity was investigated in P. aeruginosa to determine the effect of the K3 compound on bacterial chemo-signaling networks that collectively control bacterial virulence, including twitching motility, swarming motility, rhamnolipids, pyocyanin and, exopolysaccharide production. The synthesized novel hetero Zn(II)/Cu(II)-based di-nuclear complex [Zn(o-phen)LCu(OAc)], K3 compound exhibited potent antibacterial and antibiofilm properties against P. aeruginosa and S. aureus, with significant biofilm disruption, inhibition, and anti-quorum sensing effects, making it a promising candidate for further investigation as a potential antibacterial agent.

Ratiometric Fluorescence Detection of Levofloxacin Based on a Cube-like Zn(II)-Eu(III) Nanocluster: Functionalized Sodium Alginate Film for the Detection in Serum and Medicine.

A cube-like Zn(II)-Eu(III) nanocluster 1 (molecular sizes: 1.8 × 2.0 × 2.0 nm) was constructed by the use of a new long-chain Schiff base ligand. It shows a ratiometric fluorescence response to levofloxacin (LFX) with high sensitivity and selectivity, which can be expressed as I615nm/I550nm = A*[LFX]2 + B*[LFX] + C. It is used to quantitatively detect the LFX concentrations in fetal calf serum (FCS) and tablets sold in pharmacy. Filter paper strips bearing 1 can be used to qualitatively detect LFX by a color change to red under a UV lamp. 1 and its hybrid with sodium alginate (SA), 1@SA, display potential applications in the qualitative detection of LFX in FCS and the medicine. The limit of detection of 1 to LFX is as low as 2.1 × 10-2 nM.