Schiff Base HL Research Articles

Structural investigation, molecular docking, X‐ray studies, and in vitro biological activities of new transition metal complexes based isoleucine‐pyridyl hybrid Schiff base

One significant class of chemotherapeutic medicines with the ability to overcome drug resistance is metal‐based medications. The creation of novel therapeutic medications with distinct modes of action is required due to the rise in drug resistance, treatment failures, and the scarcity of available treatments. The amino acid isoleucine interacts with the arylidene (synthesized from isatin and 2,6‐diamino‐pyridine) forming the HL Schiff base ligand, which then interacts with some transition metal ions to form the metal complexes. Thermal analysis, spectroscopy (1H‐NMR, IR, mass, and ultraviolet–visible), solid reflectance, magnetic moment, molar conductivity, and elemental analyses were employed for examining the synthesized HL and resultant complexes. Mass spectra besides elemental analyses studies verified the formulae of the Schiff base ligand and metal complexes. All the complexes, except for the Fe(III) complex which is non‐electrolyte, exhibited electrolytic behavior as indicated by their molar conductivity values. The obtained complexes exhibited octahedral geometrical shapes, except for the complexes of Co(II), Ni(II), and Zn(II), which displayed tetrahedral geometry. Thermal analysis showed that the complexes consistently release organic ligands and anionic components following the initial loss of water molecules of hydration. The conducted X‐ray diffraction patterns elucidated their lattice dynamics and not only confirmed the purity of the samples, but also demonstrated that the ligand and complexes of Cr(III), Fe(III), Mn(II), Cu(II), Zn(II), and Cd(II) have a crystalline structure in addition to determination of average size of the crystallites. Scanning electron microscope (SEM) was investigated for Schiff base ligand and Co(II) complex. The complexes demonstrated superior efficacy than HL towards fungal and bacteria organisms against Aspergillus fumigatus and Candida albicans, Salmonella Sp., Bacillus subtilis, Staphylococcus aureus, and Escherichia coli. The MCF‐7 cancer cell was subjected to investigation by synthesized complexes and IC50 values ranged from 12 to 23.1 μg/ml. Molecular docking studies define and anticipate the inhibitory potential and binding mode of the generated ligand with the 1GS4, 2HQ6, 3DJD, and 5JPE receptors.

DNA interaction, biological, and structural identification studies of bivalent nano‐sized Nickel, Palladium, and Platinum chelates of 2‐(((Z)‐6‐chloro‐3‐((E)‐([2‐hydroxyphenyl]imino)methyl)‐4H‐chromen‐4‐ylidene)amino)phenol Schiff base ligand

New nano‐sized Ni(II), Pd(II), and Pt(II) Schiff base chelates of 2‐(((Z)‐6‐chloro‐3‐((E)‐([2‐hydroxyphenyl]imino)methyl)‐4H‐chromen‐4‐ylidene)amino)phenol were designed and manufactured. The structural characterization of these isolated compounds was accomplished through spectral measurements, thermal and elemental analyses, and magnetic moment and conductivity determinations. The nano‐sized metal(II) complexes molar conductance indicated that they exhibited non‐electrolytic behavior. The UV–Vis spectral data and magnetic moment provided evidence for producing octahedral geometries in the nano‐sized complexes of Ni(II), Pd(II), and Pt(II). Metal chelates' thermal characteristics and decomposition kinetics were examined through Coats‐Redfern technique. The kinetic aspects, including pre‐exponential factor (A), the entropy of activation (ΔS), and activation energy (E) were enumerated. The X‐ray diffraction (XRD) calculations results of the trivalent metal complexes showed that sharp and intense diffraction peaks signify their crystalline properties with nanoscale particle size, and another proof was obtained from the images of SEM, TEM, EDX, and AFM also homogeneous distribution over the complex surface was confirmed. Molecular modeling techniques were adopted to optimize the metal complexes geometry. The viscosity and UV–Vis absorption determinations were utilized to assess the calf thymus DNA (CT‐DNA) interaction with the nano‐sized metal(II) chelates. The acquired data revealed that the complexes exhibit a non‐intercalative or incomplete binding pattern when interacting with DNA. The calculated DNA‐complexes binding constants are 3.93 ± 0.02 × 10,4 1.67 ± 0.3 × 105 and 2.88 ± 0.03 × 105 M−1, for nano‐sized Ni(II), Pd(II) and Pt(II) Schiff base chelates, successively. Both Gram‐negative (Escherichia coli and Pseudomonas aeruginosa) and Gram‐positive (Bacillus subtilis and Streptococcus pneumoniae) micro‐organisms were tested against H2L Schiff base ligand and its nano‐sized metal(II) complexes. Candida albicans and Aspergillus fumigatus were tested for antifungal activity, revealing that most complexes had activity lower than H2L ligand, while the complex of Ni(II) exhibited no discernible antifungal activities. Furthermore, the manufactured complexes underwent testing for their in‐vitro anticancer and antibacterial effectiveness. Furthermore, the complexes antioxidant activity was appraised through DPPH and ABTS inhibition tests, revealing distinct scavenging abilities on DPPH radicals. The complexes were ordered according to their scavenging capacity as follows: Ni(II) complex > Pd(II) complex > Pt(II) complex. Finally, the study of cell cycle arrest by the Ni(II), Pd(II), and Pt(II) complexes on HEPG2 has also been performed through flow cell cytometry.

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.

Coordinated metal complexes with curcumin Schiff base: Synthesis, investigation, antibacterial screening, antioxidant studies, molecular docking and density function theory calculations

Condensation of curcumin with furfuryl amine led to the synthesis of H2L Schiff base in a 1:1 Molar ratio. Subsequently, complexes of this Schiff base with several transition metal ions were prepared also in one‐to‐one molar ratio. Multiple characterization techniques were employed to identify the structure of all compounds. Infrared, UV, proton magnetic resonance spectroscopic tests, elemental analysis, mass spectrometry, thermal analysis, molar conductivity, and density function theory (DFT) calculations were utilized to gain a comprehensive understanding of their structures. Except for the nickel (II) complex, which exhibits non‐electrolyte behavior, all complexes were found to exhibit electrolytic behavior based on molar conductivity studies. Additionally, thermogravimetric analysis was employed to learn more about the complexes' thermal breakdown and the Schiff base ligand's thermal behavior. From DFT studies, some parameters were obtained as bond angles and lengths, chemical hardness, softness, energy levels of highest occupied molecular orbital and lowest unoccupied molecular orbital, electrophilic index, dipole moment, electronegativity, and other variables. Against one or more bacterial species, it was discovered that the antibacterial activity of the metal complexes was superior to that of the free Schiff base. Furthermore, the complexes exhibited notable antioxidant activity according to the results obtained using DPPH scavenging. Overall, a detailed characterization of the synthesized compounds was performed, revealing their structural features, functional properties, and potential applications. Lastly, research on molecular docking was investigated toward all compounds against 3C1L antioxidant protein receptor.

SYNTHESIS, CHARACTERIZATION, MOLECULAR MODELING AND INVESTIGATION OF BIOLOGICAL ACTIVITY OF THE NOVEL SCHIFF BASE (E)-2-(((4-BROMOTHIOPHEN-2-YL)METHYLENE)AMINO)-5-METHYLPHENOL

The novel Schiff base derivative (E)-2-(((4-bromothiophen-2-yl)methylene)amino)-5-methylphenol (HL) was synthesized and characterized via FT-IR, elemental analysis, UV-Vis, 1H-NMR and 13C-NMR techniques. Quantum chemical calculations were performed with the density functional theory at the B3LYP level with the 6-311++G(d,p) basis tuned in the gas phase of the isolated compounds in the ground state. The thermal properties of HL Schiff base were investigated via DTA/TGA/TG curves. The antibacterial activity of the HL Schiff base against ESBL E. coli and MRSA was investigated. In the disk diffusion test, the zone of inhibition was determined against MRSA while it was not determined against ESBL E.coli. In addition, different levels of antibacterial activity were observed against all bacteria in the broth microdilution test.

Novel Schiff Base Derived from Amino Pyrene: Synthesis, Characterization, Crystal Structure Determination, and Anticancer Applications of the Ligand and Its Metal Complexes.

In this study, we report the cytotoxicity of a newly synthesized Schiff base HL ((E)-2-ethoxy-6((pyren-1-ylimino)methyl)phenol) and its derived metal complexes (Zn(II), Cu(II), Co(II), Cr(III), and Fe(III)) along with their structural characterizations by means of elemental analysis, magnetic moment, molar conductance, IR, UV-Vis, ESR, and mass spectrometry. The single X-ray diffraction of the HL shows that it exists in the phenol-imine form in its solid state. The NMR and IR data indicate that the bidentate binding of the Schiff base ligand with the metal center occurs during complexation through the azomethine nitrogen atom and the hydroxyl group oxygen atom of the 3-ethoxy salicylaldehyde. The electronic spectra and magnetic measurements indicate that the Co(II) complex has a tetrahedral geometry and that the Cr(III) and Fe(III) complexes have a distorted octahedral geometry. The ESR and electronic spectra suggest that the Cu(II) complex has a distorted tetrahedral geometry. The cytotoxic effects of the HL and all of the metal complexes were studied using human breast cancer (MCF-7) cells. The Cu(II) and Zn(II) complexes exhibited the highest activity against the tested cell line, with IC50 values of 5.66 and 12.74 μg/mL, respectively, and their activity was higher than that of the fluorouracil cancer drug against the MCF-7 cells (18.05 μg/mL).

Iminophenol as a ligand or cation in cobalt(II and II,III) complexes: synthetic approaches, spectral and structural studies

New complexes [H2L]2CoCl4 (І) and [CoІІCоІІІCl2L3]H2O (ІІ), where HL is a condensation product of o-vanillin and methylamine, were synthesized and characterized by IR, UV/Vis spectroscopies, and X-ray structural analysis. For the synthesis of I, cobalt (II) chloride was used as a metal source, while for II, cobalt powder and its salt were used simultaneously. In the preparation of I, the use of methylamine hydrochloride contributed to the formation of tetrachlorocobaltate(II) with the protonated Schiff base H2L+as a cation. The monovalent cations are almost planar and show the presence of intramolecular O/N–HО hydrogen bonds. In the crystal, columns of cations connected by - stacking alternate with double-row columns of tetrahedral [CoCl4]2– anions and are additionally joined by a branched system of O/N–HCl hydrogen bonds. Crystal II is built of neutral molecules CoІІСоІІІCl2L3 and uncoordinated water molecules. In the molecule, the main CoІІІL3 fragment with a metal atom in the octahedral environment of three deprotonated ligands attaches a cobalt(II) atom at the CoIICoIII distance of 3.17 Å. The cobalt(II) atom has a highly distorted five-coordinate СоІІО3Cl2 environment formed by two bridging oxygen atoms of deprotonated phenoxy groups, the O atom of the methoxy group of the ligands, and two chlorine atoms. The obtained results allow us to propose the use of the metal salt+its powder combination for the purposeful synthesis of mixed-valent complexes of metals capable of exhibiting various oxidation states. Deliberate protonation of the Schiff base can be used to prepare organic-inorganic metal halide hybrids with functionalized cations.

Synthesis of a new sulfadimidine Schiff base and their nano complexes as potential anti-COVID-19 and anti-cancer activity

The primary objective of this study was to describe the cytotoxicity on HEPG-2 cells and to study the COVID‑19 activities of the novel H2L ligand and its Cr and Cu nano-complexes. As well as exploring the chemistry of the prepared nano-complexes. In this paper novel Schiff base, N-(4, 6-dimethyl pyrimidin-2-yl)-4-(((2-hydroxyl naphthalene-1-y l) methylene) amino) benzene—sulfonamidesulfonyl) amide has been synthesized. The novel Schiff base H2L is used to synthesize novel nano and micro-complexes with CrCl2.6H2O and CuCl2.2H2O. The prepared ligand and micro complexes were interpreted by different spectroscopic techniques. The nano-sized Cr and Cu complexes were synthesized in an environmentally friendly manner using Coriandrum sativum (CS) media extract in ethanol. The structure, morphologies and particle size of the nano-sized complexes were determined using FT-IR, TEM, and PXRD. The results showed that the nano-domain complexes are on the Sub-nano scale. Furthermore, using TGA, we studied the effect of heat on the size of newly prepared nano-complexes. Experimental data were supported by DFT calculations. The findings revealed that the metal complexes investigated are more stable than the free ligand H2L. The antitumor activity was examined before and after heating the nano-complexes at 200 °C. The results reveal the Cr nano complex, after heating, exhibited strong antitumor activity with IC50 value (3.349 μg/ml). The tested Cu nano-complex shows good DNA cleavage. The liver cancer and COVID19 proteins were examined using molecular docking to identify the potential binding energy of inhibitors.

Solvent-regulated fluorescence off-on signaling of Ni(II) and Zn(II) with the formation of two mononuclear complexes with an ATP detection ability by Zn(II) assembly.

The current study shows that Schiff base HL, (Z)-2,4-dibromo-6-(((piperidin-2-ylmethyl)imino)methyl)phenol, can be used successfully as a selective chemosensor for Zn(II) and Ni(II) among several competing cations in purely aqueous and semi-aqueous media. Under UV light in methanol-water (9 : 1) HEPES buffer, the receptor gives its response by changing its color to cyan color in the presence of Zn(II) and to bluish cyan color in the presence of Ni(II). Surprisingly, the chemosensor can only reliably identify Zn(II) in a hundred percent aqueous medium by changing its color to light yellow. UV and fluorescence studies in both aqueous and semi-aqueous media are used to further investigate this Zn(II) and Ni(II) recognition phenomenon. The high values of the host-guest binding constants, obtained by electronic and fluorescence titration, ensure that a strong bond exists between HL and Ni(II)/Zn(II). As anticipated, two highly luminescent mononuclear, crystalline compounds, complexes 1 and 2, have been developed by a separate reaction of HL and Zn(II)/Ni(II), and the high luminous properties are due to the occurrence of Chelation Enhanced Fluorescence (CHEF). According to the single crystal structure, the asymmetric units of both complexes consist of two deprotonated chemosensor units and one Zn(II)/Ni(II), leading to the formation of an octahedral complex. For Ni(II) and Zn(II) sensing, the predicted LOD is in the nanomolar range. Both complexes 1 and 2 are fluorescence active and studies to check their ATP detection ability, but intriguingly, only complex 2 is capable of detecting ATP in a fully aqueous solution. Finally, the live cell imaging study validates the two sensors' biosensing functionality.

Theoretical investigation of the Zn2+ detection mechanism based on the quinoline derivative of the Schiff-base receptor

The sensing mechanism of the quinoline-derived Schiff base HL (concentrated from 8-hydroxyquinoline with 2,4-dihydroxybenzaldehyde) as a highly selective fluorescent probe for Zn2+ was investigated by theoretical calculations with DFT and TDDFT. The conformations of the HL molecule, its ketone form and its Zinc complex structure, were optimized in the ground and excited states. The systems have been studied in depth in terms of structural parameters, frontier molecular orbitals, absorption and fluorescence spectra as well as potential energy curves analysis and approximately density gradient analysis. The present theoretical calculations propose a different detection mechanism from that proposed experimentally. The theoretical results predict that the fluorescence quenching in HL is attributed to the excited state intramolecular proton transfer (ESIPT) rather than the photoinduced electron transfer (PET) of benzene to electrons. When Zn2+ is introduced, Zn2+ takes the place of the H atom, creating a complex that blocks the ESIPT reaction and restores fluorescence.

Synthesis, Characterization, Antioxidant and Antibacterial Activities of Six Metal Complexes Based Tetradentate Salen Type Bis-Schiff Base

Considering the importance of metal complexes in the development of medicinal chemistry, a series of transition metal complexes of Co(II), Fe(II), Zn(II), Cu(II), and Ni(II) has been synthesized from N,N'-bis(salicylidene)-2,2-dimethyl-1,3-diaminopropane H2L Schiff base ligand. The reaction of the H2L with the selected metal ions led to tetrahedral and octahedral coordinated complexes. The structural features of the obtained metal complexes were determined using analytical techniques such as FT-IR, NMR, UV-Vis, X-ray powder diffraction, mass spectrometry, and Thermogravimetry–differential thermal (TGA/DTA) analysis. The measured conductance for obtained compounds has shown the electrolytic behavior of all obtained complexes. The synthesized ligand and corresponding complexes were screened for their antioxidant and antibacterial activities. Indeed, Co(II) and Fe(II) complexes have shown excellent antioxidant activities for DPPH radical scavenging and FRAP assays, respectively. The results obtained from the disc diffusion assay showed that Co(II), Fe(II), Zn(II), and Cu(II) complexes had displayed promising antibacterial activity against Escherichia coli and Staphylococcus aureus, while no effect has been observed on both strains for ligand H2L and its corresponding Ni(II) complex.

Synthesis, crystal structure and coordination behaviors of two unexpected tetranuclear Zn(II) and Co(II) supramolecular boxes derived from structural variation of coumarin schiff base ligand

Two unexpected tetranuclear supramolecular boxes, [Zn4(L')4(CH3OH)2]·2CH3OH (1) and [Co4(L)2(L')2(CH3OH)2]·acetone (2), with M4(μ3-O)2(μ2-O)4 core were obtained through reacting coumarin Schiff base H2L (H2L = 4-hydroxy-3-((2-hydroxyphenyl-imino)-methyl)-2hchrome-2-one) with Zn(OAc)2·4H2O and Co(OAc)2·4H2O, respectively. Interestingly, the original ligand (H2L) has changed into a new structure (H2L') in the process of forming single crystals. The structures of 1 and 2 were characterized by X-ray single crystal diffraction. 1 and 2 are tetranuclear structures including four metal centers (Zn(II) or Co(II)), four completely deprotonated ligands (four new (L')2- in 1, two original (L)2- and two new (L')2- in 2), two coordinated methanol molecules and several crystalline solvent molecules. Significantly, due to the action of Zn(II) and Co(II), the original Schiff base H2L completely changed from coumarin skeleton to quinoline skeleton to form a new ligand (H2L') in 1, while in 2 half of the ligands H2L involved in coordination changed to H2L' configuration, the other half maintained the original structure. In 1, Zn1 ions are six-coordinate octahedral configuration and Zn2 are five-coordinate distorted square-pyramidal configuration with τ = 0.38. In 2, Co1 are six-coordinate octahedral configuration and Co2 are five-coordinate triangular bipyramidal configuration with τ = 0.66.

Cytotoxic urea Schiff base complexes for multidrug discovery as anticancer activity and low in vivo oral assessing toxicity

Novel mononuclear complexes 2 – 8 derived from hybrid Urea Schiff base HL were synthesized using various metal Ni 2+ , Fe 3+ , Cu 2+ , Co 2+ , Mn 2+ , Zn 2+ , and Cr 3+ . The results revealed the ligand HL reacts with metal ions as monobasic or neutral monodentate chelator it via the nitrogen of azomethine and deprotonated/protonated phenolic oxygen atom adopting octahedral geometry. The elemental analysis of the complexes showed the bonding of the ligand with the metal ions in a ratio of 1: 1 in all-metal complexes. XRD analysis of the ligand and its complexes indicate a monoclinic, tetragonal, orthorhombic corresponding to urea Shiff base (1) and zinc complex ( 7), nickel complex ( 2) , and cobalt complexes ( 5), respectively. The bioactivity of synthesized compounds was tested and screened against three cancer cell lines PC3 (prostate), SK-OV-3 (ovarian), and HeLa (cervical). The results revealed a weak activity for the ligand, whereas nickel and iron complexes present moderate activities against three cancer cells. The best results were mentioned with copper and proved the best results against three cancer cells PC3 , SKOV3, and HeLa displaying an excellent activity with IC 50 values of 0.71 ± 0.06 , 0.12 ± 0.06, and 0.79 ± 0.23 μg/mL respectively. Moreover, the urea Schiff base complexes showed good safety in vivo toxicity test. The present study demonstrates that all urea Schiff base complexes is inactive against saint tissue and five metal complexes investigated herein can be effective and promising chemotherapeutic drugs for ovarian cancer cell SKOV3, emphasizing the copper-urea Schiff base complex.

Synthesis, characterization, DFT and antibacterial studies of a novel vitamin B6 Schiff base and its Cu(II) and Zn(II) complexes

In this project, condensation reaction of the pyridoxal and 3,4-diaminopyridine resulted in a novel pyridoxal Schiff base (H2L). Synthesis and characterization by several experimental methods have been reported for the H2L species as well as its Cu(II) and Zn(II) complexes. Structural parameters, tautomerism, spectral properties and frontier orbitals of three synthesized compounds have been explored by using the density functional theory (DFT) approaches. In the square geometries for both of the complexes, the dianionic form of the Schiff base, L2- species, acts as a tetradentate ligand, coordinates to the Cu2+ and Zn2+ metal ions via two azomethine nitrogens and two phenolate oxygens. Good agreement between the experimental values and DFT-predicted IR wavenumbers and NMR chemical shifts demonstrated validity of the optimized geometries for the studied species. Also, the Atoms In Molecules (AIM) analysis was employed to characterize bonding interactions. Use of two choline chloride based eutectic solvents, as green and environmentally friendly media, resulted in high yield synthesis of the investigated species in three cycles. In addition, among the synthesized compounds, the H2L Schiff base shows great antibacterial activities.

Synthesis, characterization, and DNA binding study of ruthenium(II/III) complexes containing ONS donor Schiff base

A chelating ligand of thioether with ONS donor Schiff base HL [(E)-2-(((2-(benzylthio)phenyl)imino)methyl)napthalen-1-ol] and its metal complexes (RuL1 and RuL2) have been synthesized. They have been characterized by UV–Vis, FTIR, 1H NMR, 13C NMR, mass spectrometry methods. The formulas of the synthesized compounds have been confirmed by elemental analysis and magnetic susceptibility measurements. The binding ability studies of the ligand (HL) and its Ru complexes (RuL1 and RuL2), with calf-thymus DNA have been explored by the absorption titration method. The binding interaction study reveals that the ligand (HL) and the complex RuL1 interact with CT-DNA through an intercalative mode of binding whereas the complex RuL2 does not show any interaction with CT-DNA due to steric effect.

Syntheses, Crystal Structures, and Antimicrobial Activities of Copper(II) Complexes Derived from N,N'-Bis(5-Fluorosalicylidene)-1,3-Propanediamine

Two new Schiff base copper(II) complexes, [Cu2L2] (I) and [Cu2L(NCNCN)2]n (II), where L is the dianionic form of N,N'-bis(5-fluorosalicylidene)-1,3-propanediamine (H2L), were synthesized and characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal X-ray determinations (CIF files CCDC. nos. 2000415 (I) and 2000416 (II)). Complex I is a phenolate bridged dinuclear copper(II) compound. Complex II is a phenolate and dicyanoamide bridged polynuclear copper(II) compound. In both complexes, the Cu atoms are in square pyramidal coordination. The Schiff base ligand coordinates to the Cu atoms through the phenolate O and imino N atoms. The Schiff base H2L and the two complexes showed high selectivity and antimicrobial activities against a number of the bacteria and fungi.

Hydroxido supported and differently networked octanuclear Ni6Ln2 [Ln = GdIII and DyIII] complexes: structural variation, magnetic properties and theoretical insights.

The design and synthesis of a Schiff base H2L, (2-{[(2-hydroxy-3-methoxybenzyl)imino]methyl}phenol), bearing an ONOO donor set has been explored for its reactivity pattern with LnCl3·6H2O (Ln = GdIII and DyIII) and Ni(CH3CO2)2·4H2O in the presence of NEt3 for molecular aggregation. Coordination driven spontaneous self-assembly reactions provide [Gd2Ni6L4(μ3-OH)6(μ-OH)2(CH3CO2)2(μ-H2O)2(H2O)3(MeOH)]·8H2O (1) having a 'butterfly-shaped' core and [Dy2Ni6L4(μ3-OH)4(μ-Cl)2Cl4(H2O)2(MeOH)2]·2MeOH·4H2O (2) with a 'candy-shaped' core. Fusion of six partial cubane units led to a mineral-like core in 1, developed around the central Ni2(OH)2 moiety, whereas in the case of 2, four such partial cubanes collapsed on Dy2(OH)2. Direct-current (dc) magnetic susceptibility measurements revealed that predominant ferromagnetic interactions lead to a high-spin S = 13 ground state for 1. Complex 2 exhibits slow relaxation of magnetization under an applied small dc field with an energy barrier to reorientation of the magnetization, Ueff = 19.3 K. The static and dynamic magnetic data are analysed and corroborated by density functional theory (DFT) and detailed CASSCF based calculations.

NOO-type tridentate Schiff base ligand and its one-dimensional Cu(II) coordination polymer: Synthesis, crystal structure, biomacromolecular interactions and radical scavenging activities

N-salicylidene-2-amino5-chlorobenzoic acid, (H2L), NOO-type tridentate Schiff base and its one-dimensional Cu(II) coordination polymer, [Cu2(H2L)2(MeOH)]n, have been synthesized and characterized by CHN analysis, FTIR, 1H NMR, 13C NMR, ESI-MS and XRD techniques. Interaction of the H2L Schiff base ligand and its the Cu(II) coordination polymer with biomacramolecules {calf thymus DNA (CT-DNA) and bovine serum albumin (BSA)} has been investigated by electronic absorption and fluorescence spectroscopy. The experimental outcomes indicate that the H2L Schiff base ligand and its the Cu(II) coordination polymer bind to CT-DNA by means of a moderate intercalation mode. Furthermore, the fluorescence quenching mechanism between the H2L Schiff base ligand and its the Cu(II) coordination polymer and BSA is a static quenching process. Radical scavenging activity of the H2L Schiff base ligand and its the Cu(II) coordination polymer was determined in terms of IC50, using the DPPH and H2O2 method. In biomacromolecules interaction and radical activity studies, the Cu(II) coordination polymer was found to give better results than free the H2L Schiff base ligand.

Structural and magnetic properties of three one-dimensional nitrato-, azido- and phenoxido-bridged copper(II) coordination polymers

Three coordination polymers, 1∞[Cu3L2(NO3)]NO3·2MeOH·2H2O (1), 1∞[Cu3L2(N3)]CH3COO (2) and 1∞[Cu3L2(H2O)](ClO4)2 (3), based on the Schiff base H2L (H2L = N,N’-bis[(2-hydroxybenzilideneamino)-propyl]-piperazine) have been synthesized and characterized. X-ray single-crystal analysis shows that compounds 1 and 2 are isostructural and crystallize in a non-centrosymmetric space group, P212121, while complex 3 crystallizes in a monoclinic system, space group P21/c. Compounds 1–3 consist of trinuclear complex entities, {Cu3L2}2+, connected via different bridges, nitrato (1), azido (2) and phenoxido (3), depending on the nature of the counterion. The cryomagnetic measurements reveal weak ferromagnetic interactions between the copper(II) ions bridged by the nitrato ligands in 1 (J = +1.026 cm−1, H = -JS1S2) and a weak antiferromagnetic coupling between the copper(II) ions connected by azido groups in 2 (J = -0.295 cm−1). The exchange interaction between the copper(II) ions connected by two phenoxido groups is antiferromagnetic, J = −12.780 cm−1.

A Fluorescent Chemosensor Based on Schiff Base for the Determination of Zn2+, Cd2+and Hg2.

Metal complexes were obtained by the reaction of zinc, cadmium and mercury(II) salts with Schiff base HL (N(salicylidene)benzylamine). HL was synthesized by the condensation reaction of benzylamine and 2-hydroxybenzaldehyde. The fluorescence properties of the Schiff base and its metal complexes were studied in ethanol-water solutions. HL was examined for its utility as a fuorescent chemosensor for the determination of Zn2+, Cd2+ and Hg2+ in aqueous samples. The HL chemosensor was found to be sensitive to Zn2+, Cd2+ and Hg2+ than some metal ions and its complexes emitted strong fluorescence at 452 nm for Zn2+ at 474 nm for Cd2+ and at 491 nm for Hg2+, respectively. It was determined that HL forms complexes with a ratio of 2:1 for Zn2+ and Hg2+ and with a ratio of 1:1 for Cd2+ by Job plots. For the detection of Zn2+, Cd2+ and Hg2+ in aqueous samples, pH, solvent type and ligand concentration were optimized for an analytical method based on HL chemosensor. HL gave a wide range of linearity with Zn2+, Hg2+ and Cd2+, the limit of detection was found to be 2.7 × 10-7 M, 7.5 × 10-7 M and 6.0 × 10-7 M, respectively.