Synthesis,crystal structures,and biological properties of a new naphthalimide Schiff base and its copper(II) complex

A new naphthalimide Schiff base N-allylamine-4-(ethylenediamine-3-methoxysalicylidene)-1,8-naphthalimide (HL) and its copper(II) complex {N-allylamine-4-(ethylenediamine-3-methoxysalicylidene)-1,8-naphthalimide copper(II)} (CuL₂) have been synthesized and characterized. The crystal structure of CuL₂ has been determined by X-ray single crystal diffraction. The central Cu(II) ion is four-coordinate with an N₂O₂ donor set which is afforded by two L ligands, forming a slightly distorted square planar geometry. The interactions of HL and CuL₂ with calf thymus DNA were investigated using electronic absorption titration, fluorescence titration, and viscosity measurements. The results indicate that free HL and CuL₂ bind to DNA in an intercalation mode, and their binding affinity for DNA takes the order CuL₂ > HL. Moreover, the antioxidant assay in vitro also shows that HL and CuL₂ possess significant antioxidant activities and CuL₂ is more effective than free HL.     

A Schiff base ligand <Emphasis Type="Italic">N</Emphasis>-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its nickel(II) complex: synthesis,crystal structure,antioxidation, and DNA-binding properties

A new Schiff base ligand N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Ni complex, [Ni₂(L)₂(NO₃)₂], have been synthesized and characterized by physicochemical and spectroscopic methods. The X-ray crystal structure of [Ni₂(L)₂(NO₃)₂] shows it to be a dinuclear 2:2 complex, in which each Ni(II) atom is in a distorted octahedral geometry. The two Ni(II) atoms are dibridged by two phenoxo ligands, forming a Ni₂O₂ parallelogram-type moiety. The interactions between free HL and the complex with calf thymus DNA have been investigated, and the binding constant and linear Stern–Volmer quenching constant suggest that the two compounds bind to DNA via the intercalation mode. The binding affinity of the complex was higher than that of HL. Antioxidant assays in vitro showed that the Ni(II) complex possesses significant antioxidant activity.     

A Zn(II) luminescent complex with a Schiff base ligand: solution,computational and solid state studies

Abstract

A new mononuclear complex of zinc(II), [Zn(HL)₂]?2DMF (H₂L = (E)-N′-((E)-(hydroxyimino)butan-2-ylidene)salicyloylhydrazide, DMF = N,N-dimethylformamide), was prepared and characterized. Single-crystal X-ray crystallography revealed a six-coordinate zinc(II) surrounded by nitrogen of the oxime function and oxygen and distal nitrogens of the acylhydrazone group. This entity also exists in solution as demonstrated by ¹H-NMR and potentiometric titrations. The computational analysis showed that the molecular orbitals involved in the main electronic transitions of the complex species in solution are centered on the ligand with negligible contribution of the metal ion. The photophysical properties of the complex were evaluated in solution and in the solid state. Luminescence studies showed that the solid has a strong emission at 550 nm with a large Stokes shift with respect to absorption. The solid state fluorescence emission is ascribed to ligand-centered and/or ligand-to-ligand charge transfer transitions, following the DFT results in solution. A comparison with a previously reported mononuclear [Zn(HL)₂] allowed the investigation of the influence of DMF molecules in the structural packing and the luminescence properties.     

Syntheses,characterization and biological studies of zinc(II), copper(II) and cobalt(II) complexes with Schiff base ligand derived from 2‐hydroxy‐1‐naphthaldehyde and selenomethionine

Novel zinc(II), copper(II), and cobalt(II) complexes of the Schiff base derived from 2‐hydroxy‐1‐naphthaldehyde and D, L ‐selenomethionine were synthesized and characterized by elemental analysis, IR, electronic spectra, conductance measurements, magnetic measurements and powder XRD. The analytical data showed the composition of the metal complex to be ML(H₂O), where L is the Schiff base ligand and M = Co(II), Cu(II) and Zn(II). IR results confirmed the tridentate binding of the Schiff base ligand involving azomethine nitrogen, naphthol oxygen and carboxylato oxygen atoms. ¹H NMR spectral data of lithium salt of the Schiff base ligand [Li(HL)] and ZnL(H₂O) agreed with the proposed structures. The conductivity values of complexes between 12.50 and 15.45 S cm² mol^?1 in DMF suggested the presence of non‐electrolyte species. The powder XRD studies indicated that Co(II) complex is amorphous, whereas Cu(II) and Zn(II) complexes are crystalline. The results of antibacterial and antifungal screening studies indicated that Li(HL) and its metal complexes are active, but CuL(H₂O) is most active among them. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis,characterization, and crystal structure of two zinc(II) complexes with a Schiff base derived from amantadine

By condensation of amantadine and 4-methoxysalicylaldehyde a new Schiff base HL was synthesized. A mixture of HL and zinc(II) chloride in an alcoholic medium leads to [Zn(HL)₂Cl₂] (1). However, the same reactants gave another different complex (ZnL₂) (2) in the presence of NaOH. The two complexes were characterized by IR, ¹H NMR, elemental analysis, molar conductance, and single-crystal X-ray diffraction. X-ray diffraction analysis reveals that complex 1 crystallizes in the triclinic system, Pī space group; each asymmetric unit consists of one zinc(II), two HL, and two chlorides. The tetra coordination of central zinc is attained by two chlorides and two oxygens from the Schiff base, forming a distorted tetrahedral geometry. Complex 2 crystallizes in the monoclinic system, P2₁/c space group; each asymmetric unit consists of one zinc(II) and two L. The tetra coordination of central zinc is attained by two nitrogens and two oxygens from the Schiff base, forming a distorted tetrahedral geometry.     

Synthesis and characterization of zinc(II) and cobalt(III) Schiff base complexes

Two mononuclear complexes with the Schiff base ligand 2-((2-(dimethylamino)ethylimino)methyl)phenol (HL), namely ZnL₂ and CoL₂(N₃), have been synthesized and characterized using single-crystal X-ray diffraction and spectroscopy (IR, ¹H NMR, UV–Vis, MS and EA). Both complexes are mononuclear. The coordination geometry in the Zn(II) complex is distorted square-pyramidal with a weak Zn···N interaction. The Co(III) complex is distorted octahedral, and the neutral molecule unit [Co^IIIL₂(N₃)] is connected by C–H···N hydrogen bonds to form a one-dimensional infinite chain. The luminescence of the zinc compound has been investigated. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Synthesis,crystal structures,and antimicrobial activity of a pair of isostructural dinuclear copper(II) complexes derived from 4-nitro-2-[(2-diethylaminoethylimino)methyl]phenol

A pair of isostructural azido- or thiocyanato-bridged centrosymmetric dinuclear copper(II) complexes, [Cu₂L₂(μ_1,3-N₃)₂] (1) and [Cu₂L₂(μ_1,3-NCS)₂] (2), derived from the Schiff base ligand 4-nitro-2-[(2-diethylaminoethylimino)methyl]phenol (HL), have been synthesized and characterized by elemental analysis, IR spectra and single crystal X-ray diffraction. Each Cu atom in the complexes is five-coordinate in a square pyramidal geometry by one O and two N atoms of one Schiff base ligand, and by two terminal donor atoms from two bridging azide or thiocyanate ligands. Both the azide and thiocyanate ligands adopt end-to-end bridging mode in the complexes. The distance between the two copper atoms is 5.205(2) Å for (1) and 5.515(2) Å for (2). The antimicrobial activity of the complexes has been tested.     

A Schiff base N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine and its copper(II) coordination polymer: synthesis,crystal structure,antioxidation, and DNA-binding properties

A Schiff base, N-(2-hydroxylacetophenone)-3-oxapentane-1,5-diamine (HL) and its Cu(II) coordination polymer, [Cu(L)(NO₃)] _n , have been synthesized and characterized. [Cu(L)(NO₃)] _n is a 1?:?1 (Cu?:?L) polymer, in which copper is six-coordinate with distorted octahedral geometry. The polymer has a 1-D infinite chain structure in which coppers are bridged by a single nitrate. The interaction of HL and complex with calf thymus DNA (CT-DNA) has been investigated; the linear Stern–Volmer quenching constants (K _SV) suggest that the two compounds bind to DNA via intercalation. The binding affinity of complex was higher than HL. Antioxidant assay in vitro shows that the Cu(II) complex possesses significant antioxidant activities.     

A New Trinuclear Zn(II) Complex {[Zn(μ-ONN)(μ<Subscript>2</Subscript>-O)(μ-OO)]<Subscript>2</Subscript>Zn}: Synthesis,Characterization, Thermal Decomposition and Antibacterial Activity

New centrosymmetric trinuclear zinc(II) complex {[Zn(μ-ONN)(μ₂-O)(μ-OO)]₂Zn} has been synthesized by the reaction of a potentially ONN tridentate Schiff base ligand, and N,N-dimethylethylendiamin, with Zn(OAc)₂·2H₂O in methanol, in the refluxed conditions and characterized by elemental analysis, FT-IR and UV–Vis spectroscopy. Single crystal X-ray structure analysis reveals a trinuclear complex {[Zn(μ-ONN)(μ₂-O)(μ-OO)]₂Zn} with zinc(II) ions connected by three different bridges, (μ-ONN) of the Schiff base ligand, μ₂-O and μ-OO of the acetate. The complex is centrosymmetric, with one of the Zn atoms located at the inversion center. While the central Zn(II) ion is six-coordinated, the coordination number of the other Zn(II) ions is five. Finally, the {[Zn(μ-ONN)(μ₂-O)(μ-OO)]₂Zn} complex was thermally decomposed in air at 700 °C resulted in ZnO nano crystalites with the average size of 42 nm. The antibacterial activity of ligand and its zinc(II) complex were tested against gram-positive and gram-negative bacteria. The ligand showed higher activity than its zinc(II) complex.     

Syntheses,characterizations, crystal structures,antibacterial and SOD-like activities of nickel(II) and copper(II) complexes with 2-((Z)-(4-methoxyphenylimino)methyl)-4,6-dichlorophenol

Three mononuclear nickel(II) and copper(II) complexes, [Ni(L)₂(py)₂] (1), [Ni(L)₂(DMF)(H₂O)] (2), and [Cu(L)₂] (3), where HL = 2-((Z)-(4-methoxyphenylimino)methyl)-4,6-dichlorophenol, py = pyridine and DMF = N,N-dimethylformamide, have been synthesized and their structures determined by single crystal X-ray analysis. Complexes 1–3 crystallized in the monoclinic system of the space groups C2/c, P2_1/n, and P2_1/c, respectively. The crystal structures of 1 and 2 present an octahedral geometry at the metal center and 3 shows a square-planar geometry. The FT-IR spectra, UV–vis spectra, and magnetic susceptibility measurements agree with the observed crystal structures. EPR spectra indicate a d_x2–y2 ground state (g_|| > g_⊥ > 2.0023 and A_|| > A_⊥) for 3 at RT and LNT. The results of simultaneous TG-DTA analyses of 1 and 3 showed the final degradation products are NiO for 1 and CuO for 3. The Schiff base (HL) behaves as monobasic bidentate ligand possessing N and O donor atoms. Electrochemical properties for the complexes are similar and involve two irreversible redox processes. Complex 3 exhibits the ability to inhibit jack bean urease, although its Schiff base has no ability to inhibit urease. Complex 1 exhibits more active scavenging effects against O₂^? than HL, 2 and 3 under the same conditions. Antibacterial screening activities of these complexes were also investigated.     

Synthesis,characterisation and X-ray structure of an azido adduct of a tridentate (NNO) Schiff base nickel(II) complex

The tridentate Schiff base 1-(N-salicylideneimino)-2-(N,N-diethyl-aminoethane (HL), derived from the condensation of salicylaldehyde with N,N-diethylethylenediamine, reacted with nickel(II) nitrate and azide to give a mononuclear complex of formula [Ni(L)(N₃)], where HL?=?Et₂N(CH₂)₂NCHC₆H₄(OH). The complex was characterized by spectroscopic and X-ray crystallographic methods. Coordination around nickel(II) is square planar. The molecular and supramolecular structure of the complex is discussed.     

Coordination chemistry of [methyl-3-(4-benzyloxyphenyl)methylene]dithiocarbazate with divalent metal ions: crystal structures of the <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">S</Emphasis> Schiff base and of its bis-chelated nickel(II) complex

The condensation of 4-benzyloxybenzaldehyde with S-methyldithiocarbazate (SMDTC) yielded the Schiff base methyl-3-[(4-benzyloxyphenyl)methylene] dithiocarbazate (HL) that, upon reaction with different metal ions, afforded bis-chelated complexes, ML₂ [where M=Ni(II), Cu(II), Zn(II), Cd(II) or Pd(II)]. The ligand and all the metal complexes were characterized by physico-chemical and spectroscopic methods. The Schiff base and its bis-chelated Ni(II) complex were characterized also by single crystal X-ray analyses. The crystallographic results show that the Schiff base exists in thione tautomeric form with the dithiocarbazate fragment adopting an EE configuration with respect to the C=N bond of the group. In the NiL₂ complex, the metal is chelated by two mononegatively charged Schiff bases coordinating via the β-nitrogen and thiolate sulfur anion, generated in situ during the complexation process, and adopts a distorted square planar geometry.     

Synthesis,crystal structure,antioxidation and DNA-binding properties of a dinuclear copper(II) complex with bis(N-salicylidene)-3-oxapentane-1,5-diamine

A Schiff base bis(N-salicylidene)-3-oxapentane-1,5-diamine (H₂L) and its Cu(II) complex, [Cu₂(L)₂]?CHCl₃, have been synthesized and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray analysis revealed that the complex is a centrosymmetric binuclear neutral entity, in which Cu(II) is a five-coordinate in a distorted trigonal bipyramidal geometry. The DNA-binding properties of the free ligand and the complex have been investigated by electronic absorption, fluorescence, and viscosity measurements. The results suggest that the H₂L and the complex to DNA via the intercalation mode and the binding affinity of the complex were higher than that of the H₂L. The intrinsic binding constants K_b of the ligand and the complex are 2.2 × 10⁴ and 2.7 × 10⁴ M^?1, respectively. Antioxidant assay in vitro shows the Cu(II) complex possesses significant antioxidant activities and better scavenging activity than the H₂L and other antioxidants.     

Biomolecular docking,antimicrobial and cytotoxic studies on new bidentate schiff base ligand derived metal (II) complexes

Three new metal complexes [Cu(L)₂] (1), [Co(L)₂] (2) and [Zn(L)₂] (3) have been prepared by the reaction of hydrated salts of metal (II) acetate with new Schiff base ligand HL, [2‐((4‐(dimethylamino)phenylimino)methyl)‐4,6‐di‐t‐butylphenol] and characterized by different physico‐chemical analyses such as elemental analysis, single XRD, ¹H NMR, FTIR and UV–Vis spectroscopic techniques. Their biomolecular docking, antimicrobial and cytotoxicity studies have also been demonstrated. The proposed structure of Schiff base ligand HL and complex 2 are confirmed by Single crystal X‐ray crystallography study. This analysis revealed that metal (II) complexes remain in distorted tetrahedral coordination environments. The electronic properties such as HOMO and LUMO energies are carried out by gaseous phase DFT/B3LYP calculations using Gaussian 09 program. Complex 1 showed a good binding propensity to the DNA and HSA, during the assessment of docking studies. Schiff base ligand HL and its metal (II) complexes, 1–3 screened for their in vitro antimicrobial activities using the disc diffusion method against selected microbes. Complex 1 shows higher antimicrobial activity than complexes 2, 3 and Schiff base ligand HL. According to the results obtained from the cytotoxic studies, Schiff base ligand HL and its metal (II) complexes 1–3 have better cytotoxicity against MCF‐7 cell lines with potency higher than the currently used chemotherapeutic agent cyclophosphamide.     

Synthesis and characterization of manganese(II), nickel(II), copper(II) and zinc(II) Schiff-base complexes derived from 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine

The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-mercaptoethylamine is described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-mercaptoethylamine leads to 2,9-bis(2-ethanthiazolinyl)-1,10-phenanthroline (I) which undergoes rearrangement when reacted with manganese, nickel, copper or zinc ions to produce complexes of the tautomeric Schiff base 2,9-bis[2-(2-mercaptoethyl)-2-azaethene]-1,10-phenanthroline (L). The [M(L)Cl₂] complexes [where M = Mn(II), Ni(II), Cu(II) and Zn(II) ions] were characterized by physical and spectroscopic measurements which indicated that the ligand is a tetradentate N₄ chelating agent.     

Synthesis,crystal structure,and antibacterial activity of two new mononuclear nickel(II) complexes of a NNS Schiff base

Two new mononuclear nickel(II) complexes, [Ni(L)(N₃)] (1) and [Ni(L)₂(NCS)₂] (2), where HL = 2-{[phenyl(pyridin-2-yl)methylidene]amino}benzenethiol, a tridentate Schiff base derived from 2-aminothiophenol and 2-benzoylpyridine, have been prepared and characterized. The syntheses of 1 and 2 have been achieved by the reaction of equimolar amounts of nickel perchlorate and HL in the presence of azide and thiocyanate, respectively. The complexes have been characterized by microanalytical, spectroscopic, single-crystal X-ray diffraction, and other physicochemical studies. Structural studies reveal that 1 and 2 adopt two different geometries, distorted square planar in 1 and octahedral in 2. The two mononuclear complex units are held together by π…π or C–H…π weak intermolecular interactions to develop supramolecular networks in their solid states. The antibacterial activity of 1, 2 and their constituent Schiff base has been tested against some gram(+) and gram(?) bacteria.     

Cobalt(II), nickel(II) and copper(II) complexes of a Schiff base ligand: synthesis,structural characterization and luminescence properties

A Schiff base ligand (HL), 2,4-dimethoxy-N-(5-chloro-2-hydroxybenzylidene)-benzenamine, derived from 5-chloro-2-hydroxybenzaldehyde and 2,4-dimethoxyaniline, and its metal complexes [Co(L)₂]·CH₃OH (1), [Ni(L)₂] (2), [Cu(L)₂] (3) have been synthesized. The compounds were characterized by analytical and spectroscopic methods. In addition, the structures of the Schiff base HL and its Co(II) complex were determined by single-crystal X-ray analysis. The Co(II) center is six-coordinate, being coordinated to two imine nitrogen, two phenolate oxygen and two methoxy oxygen atoms of two crystallographically independent Schiff base ligands. Luminescence properties of HL and its complexes were investigated both in solution and in the solid state.     

Thermal behaviour of some novel antimicrobials based on complexes with a Schiff base bearing 1,2,4-triazole pharmacophore

A series of complexes of type [ML(CH₃COO)(OH₂)₂] (M: Co, Ni; HL: 2-[(E)-1H-1,2,4-triazol-3-ylimino)methyl]phenol)) and [M₂L₂(CH₃COO)₂(OH₂)_n] (M: Cu, n = 2; M: Zn, n = 0) were synthesised by template condensation. The compounds were characterised with microanalytical, ESI–MS, IR, electronic, EPR spectra and magnetic data at room temperature. Based on the IR and ESI–MS spectra, a dinuclear structure with the acetate as bridge was proposed for Cu(II) and Zn(II) complexes. The dinuclear structure of Cu(II) complex is also consistent with both magnetic behaviour and EPR spectrum. The thermal analyses have evidenced processes as water elimination, acetate decomposition, as well as oxidative degradation of the Schiff base. The final decomposition product was the most stable metal oxide as indicated by powder X-ray diffraction. The cobalt and copper compounds exhibited a broad spectrum of antibacterial activity towards both planktonic and biofilm-embedded cells. The complexes exhibit a low cytotoxicity except for Cu(II) species that induces the early apoptosis for the HEp 2 cells.     

Synthesis,Characterization and Crystal Structures of Four Dinuclear Schiff Base Nickel(II) and Copper(II) Complexes with Versatile Bridging Groups

Four novel Schiff base nickel(II) and copper(II) complexes, derived from the end‐on (μ_1,1‐N₃) azide, end‐to‐end (μ_1,3‐NCS) thiocyanate, or phenolate oxygen bridges, have been synthesized and their crystal structures determined by X‐ray diffraction methods. They are the dinuclear double end‐on azide‐bridged [Ni₂(L1)₂(MeCN)₂(μ_1,1‐N₃)₂]·MeOH ( 1 ), the dinuclear double end‐on azide‐bridged [Ni₂(L2)₂(MeOH)₂(μ_1,1‐N₃)₂][Ni₂(L2)₂(OH₂)₂(μ_1,1‐N₃)₂]·MeOH ( 2 ), the dinuclear double end‐to‐end thiocyanate‐bridged [Cu₂(L3)₂(μ_1,3‐NCS)₂] ( 3 ), and the dinuclear double phenolate O‐bridged [Cu₂(L4)₂(NCS)₂] ( 4 ), where HL1, HL2, HL3 and HL4 are four tridentate Schiff bases obtained by the condensation of 3,5‐dibromosalicylaldehyde with N‐ethylethane‐1,2‐diamine, of 3,5‐dichlorosalicylaldehyde with N‐methylpropane‐1,3‐diamine, of 3‐bromo‐5‐chlorosalicylaldehyde with 2‐aminomethylpyridine, and of 5‐nitrosalicylaldehyde with 2‐aminomethylpyridine, respectively. Each nickel(II) atom in 1 and 2 is in an octahedral coordination, while each copper(II) atom in 3 and 4 is in a square pyramidal coordination. There exists crystallographic inversion centre symmetry in each of the complexes.     

Thermal behavior of some new isatin complexes

The complexes of the type SnCl₄(HL)·EtOH and SnCl₂L₂ (HL ¹ : the Schiff base resulted in 1:1 condensation of isatin and aniline; HL ² : the Schiff base resulted in 1:1 condensation of isatin and p-toluidine) have been synthesized and characterized. The thermal analysis of the new ligands and complexes has evidenced the thermal intervals of stability and also the thermal effects that accompany them. The Schiff bases thermal transformations consist in phase transitions, C_arom–N bond cleavage and thermolysis processes. The different nature of the complexes generates their different thermal behaviour. The complexes lead in three steps to SnO₂ and in all cases the Schiff bases degradation generates a pyrrolidone-coordinated derivative. As for the SnCl₄(HL)·EtOH complexes, the SnCl₄ formed during the last step is involved in two competitive processes, one consists in their volatilisation while the other one leads to SnO₂. As result the SnO₂ residue is smaller than the theoretically expected.