Study on synthesis, crystal structure, antioxidant and DNA-binding of mono-, di- and poly-nuclear lanthanides complexes with bis(N-salicylidene)-3-oxapentane-1,5-diamine

Modulation of proteins by rare earth elements as a biotechnological tool

Although rare earth element (REE) complexes are often utilized in bioimaging due to their photo- and redox stability, magnetic and optical characteristics, they are also applied for pharmaceutical applications due to their interaction with macromolecules namely proteins. The possible implications induced by REEs through modification in the function or regulatory activity of the proteins trigger a variety of applications for these elements in biomedicine and biotechnology. Lanthanide complexes have particularly been applied as anti-biofilm agents, cancer inhibitors, potential inflammation inhibitors, metabolic elicitors, and helper agents in the cultivation of unculturable strains, drug delivery, tissue engineering, photodynamic, and radiation therapy. This paper overviews emerging applications of REEs in biotechnology, especially in biomedical imaging, tumor diagnosis, and treatment along with their potential toxic effects. Although significant advances in applying REEs have been made, there is a lack of comprehensive studies to identify the potential of all REEs in biotechnology since only four elements, Eu, Ce, Gd, and La, among 17 REEs have been mostly investigated. However, in depth research on ecotoxicology, environmental behavior, and biological functions of REEs in the health and disease status of living organisms is required to fill the vital gaps in our understanding of REEs applications.

A Eu3+doped functional core-shell nanophosphor as fluorescent biosensor for highly selective and sensitive detection of dsDNA

Lanthanide-doped core-shell nanomaterials have illustrated budding potential as luminescent materials, but their biological applications have still been very limited due to their aqueous solubility and biocompatibility. Here, we report a simple and cost-effective approach to construct a water-stable chitosan-functionalized lanthanoid-based core shell (Ca-Eu:Y2O3@SiO2) nanophosphor. The as-synthesized Ca-Eu:Y2O3@SiO2-chitosan (CEY@SiO2-CH) nanophosphor has been characterized for its structural, morphological, and optical properties, by employing different analytical tools. This sensing platform is suitable for dsDNA probing by tracing the "turn on" fluorescence signal generated by CEY@SiO2-CH nanophosphor with the addition of dsDNA. The ratio of fluorescence intensity enhancement is proportional to the concentration of dsDNA in the range 0.1-90 nM, with the limit of detection at ⁓16.1 pM under optimal experimental conditions. The enhancement in fluorescence response of functionalized core-shell phosphor with dsDNA is due to the antenna effect. Additionally, response of probe has been studied for the real samples displaying percent recovery in between 101 and 105, maximum RSD% upto 5.23 (n = 3). This outcome can be applied to the selective sensing of dsDNA through optical response. These findings establish the CEY@SiO2-CH a simple, portable, and potential candidate as a sensor for rapid and analytical detection of dsDNA.

Structural Study of a La(III) Complex of a 1,2,3-Triazole Ligand with Antioxidant Activity

The 1,2,3-triazole derivative 2-(4-chlorophenyl)-5-(pyrrolidin-1-yl)-2H-1,2,3-triazole-4-carboxylic acid with potential anticancer activity was used as a ligand in complex formation with the lanthanum(III) ion. The molecular structure and vibrational spectra of the complex were optimized at three DFT levels, and the scaled IR and Raman spectra were compared to the experimental ones. Several scaling procedures were used. Through a detailed analysis, the structure predicted for the newly synthetized La(III) complex was confirmed by the good accordance of the calculated/experimental IR and Raman spectra. The best DFT method appeared to be M06-2X with the Lanl2mb basis set, followed closely by Lanl2dz. The effect of the lanthanide atom on the molecular structure and atomic charge distribution of the triazole ring was evaluated. The potential free radical scavenging activity of both the ligand and the complex was investigated in several radical-generating model systems. The potential mechanisms of antioxidant action (hydrogen atom transfer (HAT) and single-electron transfer (SET)) were elucidated.

Hantzsch-Like Synthesis, DNA Photocleavage, DNA/BSA Binding, and Molecular Docking Studies of Bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) Analogs Linked to Naphthalene Core

The cyclocondensation reaction of aldehydes with dimedone and bis(6-aminopyrimidin-4-one) in acetic acid led to the formation of the corresponding bis(pyrimido[4,5-b]quinoline-4,6-diones) which are known as bis(sulfanediyl)bis(tetrahydro-5-deazaflavin) analogs in a single step. Also, bis(pyrimido[4,5-b]quinoline-4,6-diones) which are linked to naphthyl core via phenoxymethyl linkage is prepared. The interactions of the synthesized compounds with DNA and bovine serum albumin (BSA) were studied. Gel electrophoresis assay was used to show the capability of the compounds to photocleave the supercoiled pBR322 plasmid DNA in UV-A (365 nm). Besides, the most photocleavable compound, bis(tetrahydropyrimido[4,5-b]quinoline-4,6-dione) linked to pyridin-3-yl at position-5 exhibits good binding affinities toward CT-DNA and BSA as supported by UV/VIS spectral studies. In addition to the experimental findings, a molecular docking simulation was performed to collect detailed binding data for this compound to both biomolecules.

Two new lanthanide complexes with 5-(Pyrazol-1-yl)nicotinic acid: Structures and their anti-cancer properties

Two new lanthanide complexes [PrL₂(EA)₂]NO₃ (complex 1) and [SmL₂(EA)₂]NO₃ (complex 2) (H₂L = 5-(Pyrazol-1-yl)nicotinic acid, EA = CH₃CH₂OH) were synthesized. The structures were characterized by single crystal X-ray and elemental analysis. The interaction between the complex and fish sperm DNA(FS-DNA) was monitored using ultraviolet and fluorescence spectroscopy, and the binding constants were determined. Both complexes showed the ability to effectively bind DNA, and the molecular docking technology was used to simulate the binding of the complex and DNA. In addition, through the annexin V-Fluorescein Isothiocyanate(FITC)/ Propidium Iodide (PI) test experiment, tetrazollium [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide(MTT) in vitro test, and cell morphology apoptosis studies, it was shown that the complex can effectively induce HeLa tumor cell apoptosis. Compared with cisplatin and complex, complex 1 shows significant cancer cell inhibition, and we hope that this new type of complex will open up new ways for the next generation of drugs in biomedical applications.

Synthesis, characterization and anticancer activity of Fe(II) and Fe(III) complexes containing N-(8-quinolyl)salicylaldimine Schiff base ligands

A series of Fe(II) complexes (1-4) and Fe(III) complexes (5-8) from Fe(II)/(III) chloride and N-(8-quinolyl)-X-salicylaldimine Schiff base ligands (Hqsal-X2/X: X = Br, Cl) were successfully synthesized and characterized by spectroscopic (FT-IR, 1H-NMR), mass spectrometry, thermogravimetric analysis (TGA), and single crystal X-ray crystallographic techniques. The interaction of complexes 1-8 with calf thymus DNA (CT-DNA) was determined by UV-Vis and fluorescence spectroscopy. The complexes exhibited good DNA-binding activity via intercalation. The molecular docking between a selected complex and DNA was also investigated. The in vitro anticancer activity of the Schiff base ligands and their complexes were screened against the A549 human lung adenocarcinoma cell line. The complexes showed anticancer activity toward A549 cancer cells while the free ligands and iron chloride salts showed no inhibitory effects at 100 µM. In this series, complex [Fe(qsal-Cl2)2]Cl 6 showed the highest anticancer activity aginst A549 cells (IC50 = 10 µM). This is better than two well-known anticancer agents (Etoposide and Cisplatin). Furthermore, the possible mechanism for complexes 1-8 penetrating A549 cells through intracellular ROS generation was investigated. The complexes containing dihalogen substituents 1, 2, 5, and 6 can increase ROS in A549 cells, leading to DNA or macromolecular damage and cell-death induction.

Chiral Lanthanide Complexes with l- and d-Alanine: An X-ray and Vibrational Circular Dichroism Study

A whole series of [Ln(H2O)4(Ala)2]26+ dimeric cationic lanthanide complexes with both L- and D-alanine enantiomers was synthesized. The single-crystal X-ray diffraction at 100 and 292 K shows the formation of two types of dimers (I and II) in crystals. Between the dimer centers, the alanine molecules behave as bridging (μ2-O,O'-) and chelating bridging (μ2-O,O,O'-) ligands. The first type of bridge is present in dimers I, while both bridge forms can be observed in dimers II. The IR and vibrational circular dichroism (VCD) spectra of all L- and D-alanine complexes were registered in the 1750-1250 cm-1 range as KBr pellets. Despite all the studied complexes are exhibiting similar crystal structures, the spectra reveal correlations or trends with the Ln-O1 distances which exemplify the lanthanide contraction effect in the IR spectra. This is especially true for the positions and intensities of some IR bands. Unexpectedly, the ν(C=O) VCD bands are quite intense and their composed shapes reveal the inequivalence of the C=O vibrators in the unit cell which vary with the lanthanide. Unlike in the IR spectra, the ν(C=O) VCD band positions are only weakly correlated with the change of Ln and the VCD intensities at most show some trends. Nevertheless, this is the first observation of the lanthanide contraction effect in the VCD spectra. Generally, for the heavier lanthanides (Ln: Dy-Lu), the VCD band maxima are very close to each other and the mirror reflection of the band of two enantiomers is usually better than that of the lighter Lns. DFT calculations show that the higher the multiplicity the higher the stability of the system. Actually, the molecular geometry in crystals (at 100 K) is well predicted based on the highest-spin structures. Also, the simulated IR and VCD spectra strongly depend on the Ln electron configuration but the best overall agreement was reached for the Lu complex, which is the only system with a fully filled f-shell.

A Newly Synthesized Heterobimetallic NiII-GdIII Salamo-BDC-Based Coordination Polymer: Structural Characterization, DFT Calculation, Fluorescent and Antibacterial Properties

A unprecedented hetero-bimetallic 3d-4f BDC-salamo-based coordination polymer, [(L)Ni(BDC)Gd(NO3)(DMF)] was prepared and validated via elemental analyses, IR and UV–Visible absorption spectra, DFT calculation, and X-ray crystallography. The six-coordinated Ni1 ion lies at the N2O2 donor site of the L2− moiety, and one DMF O atom and carboxylate O atom occupy, collectively, the axial positions, and form a twisted octahedron. The nine-coordinated Gd1 ion consists of three oxygen atoms (O12, O13, and O14) of two carboxylate groups, two oxygen atoms (O8 and O9) derived from one bidentate nitrate group, and an O2O2 coordination site (O1, O2, O6, and O5) of the L2− unit, forming a twisted three-capped triangular prism coordination geometry. Compared to the ligand (H2L), the fluorescence intensity decreases due to the coordination of metal ions. Meanwhile, the antibacterial activities are researched.

Four rare structurally characterized hetero-pentanuclear [Zn4Ln] bis(salamo)-type complexes: syntheses, crystal structures and spectroscopic properties

Four new hetero-pentanuclear 3d–4f complexes [Zn₄(L)₂La(NO₃)₂(OEt)(H₂O)] (1), [Zn₄(L)₂Ce(NO₃)₂(OMe)(MeOH)] (2), [Zn₄(L)₂Pr(NO₃)₂(OEt)(EtOH)] (3) and [Zn₄(L)₂Nd(NO₃)₂(OMe)(MeOH)] (4) were synthesized by the reactions of a newly synthesized octadentate bis(salamo)-based tetraoxime ligand (H₄L) with Zn(OAc)₂·2H₂O and Ln(NO₃)₃·6H₂O (Ln = La, Ce, Pr and Nd), respectively, and characterized via elemental analyses, FT-IR, UV-Vis spectroscopy and single crystal X-ray crystallography. The X-ray crystallographic investigation revealed that all Zn^II ions were located in N₂O₃ coordination spheres, and possessed a trigonal bipyramid coordination environment. The Ln^III ion lay in an O₈ coordination sphere, and adopted a distorted square antiprismatic coordination environment. Furthermore, supramolecular interactions and fluorescence properties were investigated.

Four new hetero-pentanuclear 3d–4f complexes 1–4 were synthesized and characterized. Supramolecular interactions and fluorescence properties of complexes 1–4 were investigated.

Synthesis, crystal structure and biological properties of Cd and Zn coordination polymers based on a flexible tripodal ligand

Two new coordination polymers, namely poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}tricadmium(II)] 3.5-hydrate], {[Cd3(SCN)6(C18H21N9)4]·3.5H2O} n (1), and poly[[hexathiocyanatotetrakis{μ3-2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene}trizinc(II)] 3.5-hydrate], {[Zn3(SCN)6(C18H21N9)4]·3.5H2O} n (2), have been synthesized under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy and single-crystal X-ray diffraction analysis. From the X-ray analysis, it is noteworthy that polymers 1 and 2 are isostructural, with their three-dimensional structures composed of three kinds of four-connection metal ions and two kinds of three-connection 2,4,6-trimethyl-1,3,5-tris[(triazol-1-yl)methyl]benzene (TTTMB) ligand nodes. Each metal ion is six-coordinated in a slightly distorted octahedral geometry. The antioxidant activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) and the antidiabetic activity against α-amylase of the synthesized compounds were evaluated in vitro. The results of the DPPH free-radical scavenging assay showed that polymers 1 and 2 exhibited strong antioxidant effects, with IC50 values of 3.81 and 2.56 mg ml−1, respectively. The IC50 value in the antidiabetic studies of polymer 1 was 3.94 mg ml−1, while polymer 2 exhibited no antidiabetic activity. Polymers 1 and 2 revealed different inhibitory activities on DPPH and α-amylase, which indicated that the metal ions play important roles in the biological activity of coordination polymers. In addition, the solid-state photoluminescence properties and thermal stability of 1 and 2 have been investigated.

DNA binding studies of antibiotic drug cephalexin using spectroscopic and molecular docking techniques

The purpose of this study was to explore an accurate characterization of the binding interaction of antibiotic drug cephalexin with calf thymus DNA (CT-DNA) as a relevant biological target by using UV absorption, fluorescence spectroscopy and circular dichroism (CD) in vitro under simulated physiological conditions (pH = 7.4) and also through a molecular modeling study. The results showed that the drug interacts with the DNA helix via a minor groove binding mode. The thermodynamic parameters were calculated and showed that the reaction between the drug and CT-DNA was exothermic. In addition, the drug enforced traceable changes in the viscosity of DNA. The molecular modeling results indicated that cephalexin forcefully binds to the minor groove of DNA with a relative binding energy of -21.02 kJ mol^-1. The obtained theoretical results were in good agreement with those obtained from experimental studies.

Luminescent and electrochemical properties of four novel butterfly-shaped hetero-pentanuclear [Zn4Ln] complexes constructed from a bis(salamo)-type ligand

Four novel butterfly-shaped hetero-pentanuclear 3d-4f complexes [Zn₄(L)₂Sm(H₂O)₄]3NO₃·2EtOH (1) [Zn₄(L)₂Eu(NO₃)₂(MeOH)(EtOH)]NO₃·H₂O (2), [Zn₄(L)₂Gd(H₂O)₄]3NO₃·MeOH·EtOH (3) and [Zn₄(L)₂Tb(NO₃)(EtOH)(H₂O)₂]NO₃·MeOH·EtOH (4) were synthesized by the reactions of a bis(salamo)-type tetraoxime ligand (H₄L) with Zn(OAc)₂·2H₂O and Ln(NO₃)₃·6H₂O (Ln = Sm, Eu, Gd and Tb), respectively. The structures of complexes 1-4 were fully characterized by elemental analyses, FT-IR, UV-Vis spectroscopy and single crystal X-ray crystallography, and their luminescence properties were also discussed. In addition, cyclic voltammograms were used to characterize electrochemical properties of the Zn(II)-Ln(III) (Ln = Sm, Eu, Gd and Tb) complexes.

Synthesis and Fluorescence Properties of a Structurally Characterized Hetero-Hexanuclear Zn(II)-La(III) Salamo-Like Coordination Compound Containing Auxiliary Ligands

A hetero-hexanuclear Zn(II)-La(III) coordination compound, [{(ZnL)2La}2(bdc)2](NO3)2 (H2bdc = terephthalic acid) has been synthesized with a symmetric Salamo-like bisoxime, and characterized by elemental analyses, IR, UV-Vis, fluorescent spectroscopy, and single-crystal X-ray diffraction analysis. All of the Zn(II) ions are pentacoordinated by N2O2 donator atoms from the (L)2− unit and one oxygen atom from one terephthalate anion. The Zn(II) ions adopt trigonal bipyramidal geometries (τZn1 = 0.61, τZn2 = 0.56). The La(III) ions are decacoordinated in the Zn(II)-La(III) coordination compound and has a distorted bicapped square antiprism geometry. Meanwhile, the photophysical property of the Zn(II)-La(III) coordination compound was also measured and discussed.

Homo- and heterometallic Cu(II)-M(II) (M = Ca, Sr and Ba) bis(salamo)-based complexes: Syntheses, structures and fluorescent properties

Four homo/heterometallic complexes [Cu₃(L)(μ₂-OAc)₉(CH₃OH) ₉]·3CHCl₃ (1), [Cu₂(L)Ca(μ₂-NO₃)₉] (9), [{Cu₂(L)Sr(μ₂-NO₃)₉}₉]·CH₃CH₂OH (11) and [Cu₂(L)Ba(μ₂-OAc)₉(OAc)] (14), containing an acyclic naphthalenediol-based ligand H₄L, were synthesized and characterized by elemental analyses, IR, UV-Vis, fluorescence spectra, TG-DTA and X-ray crystallography. The complex 1 was obtained by the reaction of H₄L with 11 equivalents of Cu(OAc) ₉·2H₂O. The heterometallic complexes 9, 11, 14 were acquired by the reaction of H₄L with 9 equivalents of Cu(OAc)₉·2H₂O or Cu(NO₃)₉·2H₂O and 1 equivalent of M(OAc)₉ (M = Ca, Sr and Ba). Owing to the different coordination cavities of the N₂O₂ and O₆ of the completely deprotonated (L)^14- unit, the crystal structures showed the N₂O₂ sites were occupied by Cu(II) atoms, alkaline earth metal(II) atoms occupied the O₆ site of the ligand (L)^14- unit, respectively. Furthermore, the fluorescence properties and TG-DTA analyses were discussed.

Unusual constructions of two Salamo-based copper(II) complexes

wo unusual Cu(II) complexes [{Cu(L¹)}₂] (1) and [Cu₂(L²)] (2), with an asymmetric salamo-type bisoxime ligand H₂L¹ were synthesized and characterized by elemental analyses, UV-Vis, fluorescent spectra, Hirshfeld surface analyses and single-crystal X-ray diffraction analyses. For the complex 1, two Cu(II) ions are penta-coordinate by N₂O₂ donor atoms from the (L¹)^2- unit and one bridged phenol oxygen atom from another (L¹)^2- unit. Complex 1 does not have intermolecular hydrogen bonds, formed an isolated zero dimensional structure. Meanwhile, for the complex 2, an unexpected ligand H₄L² was synthesized by aldol condensation reaction of H₂L¹ and acetone upon coordination, then the new ligand and Cu(II) ions combined, formed a highly symmetrical structure, and two Cu(II) ions of the complex 2 have tetra-coordinate environment. With the help of intermolecular hydrogen bonding CH⋯O interactions, a self-assembled infinite 1D supramolecular structure was formed. Meanwhile, the photophysical spectra and Hirshfeld surface analyses of the complexes 1 and 2 were also measured and discussed.

Exploration and application of a highly sensitive bis(salamo)-based fluorescent sensor for B4O72- in water-containing systems and living cells

A highly selective fluorescent sensor H4L based on a bis(salamo)-type compound with two N2O2 chelating moieties as ionophore was successfully developed. Sensor H4L was found to have excellent selectivity for B4O72- over many other anions (Br-, CI-, CN-, CO32-, HCO3-, H2PO4-, HSO4-, NO3-, OAc-, S2O3-, SCN-, SO42-, Hcy (homocysteine) and H2O2), and it exhibited an approximately 150-fold enhancement of the fluorescence response to B4O72- in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Significantly, its fluorescence intensity was enhanced in a linear fashion with increasing concentrations of B4O72-. The detection limit of sensor H4L towards B4O72- was 8.61 × 10-7 M. The test strips could conveniently, efficiently and simply detect B4O72- ions in Tris-HCl buffer (DMF/H2O = 9:1, v/v, pH = 7) solutions. Furthermore, sensor H4L showed excellent membrane permeability in living cells, and it was successfully used to monitor intracellular B4O72- by confocal luminescence imaging.

A heterotrimetallic Ni(II)–Dy(III) bis(salamo)-based complex: synthesis, structure and fluorescent property

A discrete heterotrinuclear complex [{Ni2LDy(OAc)3(CH3OH)}2] · 2CH3OH · 3CH2Cl2, with a naphthalenediol-based acyclic bis(salamo) ligand H4L, has been synthesized and structurally characterized using elemental analyses, IR, UV/Vis and fluorescence spectra and single crystal X-ray diffraction. The crystal structure shows two crystallographically independent but chemically identical molecules (moleculesIandII). All the Ni(II) atoms are hexa-coordinated with slightly distorted octahedral geometries. The central Dy atoms are nona-coordinated with slightly distorted tricapped trigonal prism geometries. An infinite 3D supramolecular structure is formed via intermolecular hydrogen bonding and C–H…π interactions.

Crystal structure of bis{5-methoxy-2-(((2-oxo-2H-chromen-6-yl)imino)methyl)phenolato-κ2 N,O}zinc(II), C34H24N2O8Zn

C34H24N2O8Zn, triclinic, P1̅ (no. 2), a = 9.1202(6) Å, b = 12.2985(8) Å, c = 12.9973(9) Å, α = 83.799(2)°, β = 76.063(2)°, γ = 81.385(2)°, Z = 2, V = 1395.02(16) Å3, R gt(F) = 0.0292, wR ref(F 2) = 0.0691, T = 296(2) K.

Unprecedented Fluorescent Dinuclear CoII and ZnII Coordination Compounds with a Symmetric Bis(salamo)-Like Tetraoxime

Two unprecedented homometallic Co^II and Zn^II coordination compounds, [M₂(L)(OCH₃)][M₂(L)(OAc)] (M^II = Co^II (1) and Zn^II (2)), with a novel symmetric bis(salamo)-like tetraoxime ligand H₃L were synthesized and characterized by elemental analyses, infrafred (IR), ultraviolet–visible spectroscopy (UV-Vis), fluorescent spectra and single-crystal X-ray diffraction analyses. The unit cell of the two coordination compounds contains two crystallographically and chemically independent dinuclear coordination compounds. In the two coordination compounds, three metal ions are five-coordinated, formed two square pyramidal and a trigonal bipyramidal geometries, and the other metal ion is a hexacoordinate octahedral configuration. In addition, the coordination compound 1 forms a 3D supramolecular structure, and the coordination compound 2 forms a 0D dimer structure by the inter-molecular hydrogen bond interactions. Meanwhile, the fluorescence spectra of the coordination compounds 1 and 2 were also measured and discussed.

Synthesis and Fluorescence Properties of Structurally Characterized Heterobimetalic Cu(II)⁻Na(I) Bis(salamo)-Based Complex Bearing Square Planar, Square Pyramid and Triangular Prism Geometries of Metal Centers

A novel heterotrinuclear complex [Cu₂(L)Na(µ-NO₃)]∙CH₃OH∙CHCl₃ derived from a symmetric bis(salamo)-type tetraoxime H₄L having a naphthalenediol unit, was prepared and structurally characterized via means of elemental analyses, UV-Vis, FT-IR, fluorescent spectra and single-crystal X-ray diffraction. The heterobimetallic Cu(II)–Na(I) complex was acquired via the reaction of H₄L with 2 equivalents of Cu(NO₃)₂·2H₂O and 1 equivalent of NaOAc. Clearly, the heterotrinuclear Cu(II)–Na(I) complex has a 1:2:1 ligand-to-metal (Cu(II) and Na(I)) ratio. X-ray diffraction results exhibited the different geometric behaviors of the Na(I) and Cu(II) atoms in the heterotrinuclear complex; the both Cu(II) atoms are sited in the N₂O₂ coordination environments of fully deprotonated (L)⁴⁻ unit. One Cu(II) atom (Cu1) is five-coordinated and possesses a geometry of slightly distorted square pyramid, while another Cu(II) atom (Cu2) is four-coordination possessing a square planar coordination geometry. Moreover, the Na(I) atom is in the O₆ cavity and adopts seven-coordination with a geometry of slightly distorted single triangular prism. In addition, there are abundant supramolecular interactions in the Cu(II)–Na(I) complex. The fluorescence spectra showed the Cu(II)–Na(I) complex possesses a significant fluorescent quenching and exhibited a hypsochromic-shift compared with the ligand H₄L.

Isatin based macrocyclic Schiff base ligands as novel candidates for antimicrobial and antioxidant drug design: In vitro DNA binding and biological studies

In the present work, five macrocyclic compounds, C₁₈H₁₂N₂O₄ (1), C₃₈H₂₄N₈O₆ (1a), C₃₈H₂₄N₈O₄S₂ (1b), C₄₀H₃₂N₈O₄ (2a) and C₄₈H₃₂N₈O₄ (2b) have been synthesized and thoroughly characterized by elemental analysis, FT-IR, 1D & 2D NMR and electron spray ionization mass spectral analysis. The DNA binding ability of these compounds were investigated in vitro by UV-Visible, fluorescence, circular dichroism (CD) spectroscopy and viscosity measurements. The results indicate that these compounds possess strong DNA binding affinity via intercalation, while the order of binding strength followed the trend 2b (1.52 ± 0.06 × 10⁵ M^-1) > 2a (1.12 ± 0.11 × 10⁵ M^-1) > 1b (1.05 ± 0.04 × 10⁵ M^-1) > 1a (0.97 ± 0.14 × 10⁴ M^-1) > 1 (0.75 ± 0.21 × 10⁴ M^-1). The radical scavenging potencies of the compounds were explored by employing DPPH, OH and NO assays, in which 1a exhibited highest inhibitory effect on the radicals (IC₅₀ = 23.59 μM (DPPH), 26.14 μM (OH), 28.41 μM (NO)). The in vitro antibacterial studies showed that these compounds have the potential to arrest the growth of bacteria, among which, 1a was found to be vulnerable against the bacterial stains. In addition, in silico molecular docking stimulations were also performed to position these compounds into the active sites of bacterial membrane proteins. The results of in vitro and in silico investigations reveal that the compounds apprehend the bacterial growth significantly. The data obtained from this piece of work would be helpful to design antibacterial drugs incorporating isatin based macrocyclic frameworks.

Structural and Luminescent Properties of Heterobimetallic Zinc(II)-Europium(III) Dimer Constructed from N2O2-Type Bisoxime and Terephthalic Acid

A new heterohexanuclear ZnII–EuIII dimer [{(ZnL)2Eu}2(bdc)2]·2Cl constructed from a N2O2-type chelating ligand H2L (6,6′-Dimethoxy-2,2′-[ethylenedioxybis(nitrilomethylidyne)]diphenol), Zn(OAc)2·2H2O, EuCl3·6H2O and H2bdc (terephthalic acid) was synthesized, and characterized using elemental analyses, IR (Infrared), UV-Vis (Ultraviolet–visible) spectra and X-ray single crystal diffraction method. There are two crystallographically equivalent [(ZnL)2Eu] moieties in the ZnII–EuIII complex, the two [(ZnL)2Eu] moieties are linked by two bdc2– ligand leading to a heterohexanuclear dimer, in which the carboxylato groups bridge the ZnII and EuIII atoms. Furthermore, the luminescence properties of H2L and its ZnII–EuIII complex have been studied.

Synthesis and Fluorescence Properties of a New Heterotrinuclear Co(II)-Ce(III)Complex Constructed from a bis(salamo)-Type Tetraoxime Ligand

[Co₂(L)Ce(OAc)₃(CH₃CH₂OH)]·1.5CH₃OH∙0.5CH₂Cl₂, a heterotrinuclear Co(II)-Ce(III) bis(salamo)-type complex with a symmetric bi(salamo)-type ligand H₄L and an acyclic naphthalenediol moiety, was designed, synthesized and characterized by elemental analyses, FT-IR, UV-Vis and fluorescence spectroscopy and X-ray crystallography. The X-ray crystallographic investigation revealed the heterotrinuclear complex consisted of two Co(II) atoms, one Ce(III) atom, one (L)^4‒ unit, three μ₂-acetate ions, one coordinated ethanol molecule, one and half crystallization methanol molecule and half crystallization dichloromethane molecule. Two Co(II) atoms located in the N₂O₂ coordination spheres, are both hexacoordinated, with slightly distorted octahedral geometries. The Ce(III) atom is nine-coordinated and located in the O₆ cavity possesses a single square antiprismatic geometry. In addition, supramolecular interactions exist in the Co(II)-Ce(III) complex. Two infinite 2D supramolecular structures are built via intermolecular O-H···O, C-H···O and C-H···π interactions, respectively.