Copper (II) and silver (II) complexes of polymer-bound porphyrins with Schiff base linkage

Two percent divinylbenzene (DVB)–crosslinked polystyrene was prepared and functionalized to obtain its aldehyde analog. Amino porphyrins were anchored on this polymer support by Schiff base condensation. The anchoring positions were adjusted so as to obtain ortho-, meta-, and para-isomeric systems. The polymer-bound free-base porphyrins were metallated to obtain the corresponding Cu(II) and Ag(II) complexes by treating them with the corresponding metal salt solutions. The products were characterized chemically and spectroscopically. Electronic and ESR spectral analysis shows the microenvironmental participation of the polymer network on the electronic levels of the porphyrin system. The extents of steric and electronic participation were evaluated and are presented. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 89–93, 1998     

Synthesis,characterization and DNA interaction of copper (II) complexes with Schiff base ligands derived from 2-pyridinecarboxaldehyde and polyamines

A series of copper (II) complexes a–d with Schiff bases ligands derived from the condensation reactions between 2-pyridinecarboxaldehyde and different polyamines (ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine) were synthesized and characterized by elemental analysis, FT-IR spectroscopy, HRMS, molar conductance and molecular modeling studies. The interactions of the copper complexes a–d with DNA were investigated by the UV spectra, viscosity measurements and gel electrophoresis under physiological conditions. The experimental results indicated that four complexes could bind to DNA via an intercalative mode and showed a different DNA cleavage activity with the sequence: d > c > a > b.     

Dinuclear based polymeric copper(II) complexes derived from a Schiff base ligand: effect of secondary bridging moieties on geometrical orientations and magnetic properties

[1 + 1] condensation of salicylaldehyde and 2-aminobenzenesulfonic acid led to the formation of the acyclic Schiff base o-[(o-hydroxyphenyl)methylideneamino]benzenesulfonic acid (H₂L) which, upon reaction with Cu(II) salts in the presence of triethylamine or 4,4′-bipyridine, formed a 2D polymeric species [Cu₂L₂]_n (1) via sulfonate bridge and a 1D polymeric complex [{Cu₂L₂(4,4′-bipy)}·DMF]_n (2) via 4,4′-bipyridine bridge, respectively. The copper cations sit on O₄N basal- or O₃N₂ facial-edge-sharing inverted square pyramidal environments in 1 or 2, respectively. In spite of their comparable compositions, the relative orientations of the metal polyhedra affect the magnetic properties of these polymers since 1, in contrast to 2, presents a strong exchange interaction of an antiferromagnetic nature.     

A mononuclear copper(II) complex of a protonated unsymmetrical dinucleating Schiff base ligand

Reaction of the unsymmetrical and potentially dinucleating Schiff base ligand HL¹ with copper(II) salts has given mono- and dinuclear metal complexes. The structure of a mononuclear complex of diprotonated HL¹, [Cu(H₂L¹)(OH₂)](ClO₄)₃·H₂O·CH₃OH_, has been determined.     

Synthesis,characterization and biomolecular interactions of Cu(II) and Ni(II) complexes of acyclic Schiff base ligand

Mononuclear copper(II) (1) and nickel(II) complexes (2) of acyclic Schiff base ligand, N,N′-bis(2-hydroxy-1-naphthyl)-1,4-bis(3-iminopropyl) piperazine (L) were synthesized and characterized. The molecular structure of the ligand was confirmed using single crystal X-ray diffraction analysis. The complexes displayed good binding abilities to bovine serum albumin protein (BSA). The binding interactions of complexes 1 and 2 with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroism spectral analysis and molecular docking studies. Complex 1 showed greater interaction with DNA than nickel(II) complex 2. The cleavage studies with pBR322 DNA showed efficient oxidative cleavage in the presence of 3-mercaptopropionicacid (MPA) and for hydrogen peroxide for complexes 1 and 2 respectively.     

Square-planar nickel(II) complexes with a tridentate Schiff base and monodentate heterocycles: self-assembly to dimeric and one-dimensional array via hydrogen bonding

Two nickel(II) complexes having the general formula [Ni(bhac)L] with tridentate ONO-donor acetylacetone benzoylhydrazone (H₂bhac) and monodentate N-donor heterocycles (L=3,5-dimethylpyrazole (Hdmpz) and imidazole (Himdz)) are reported. The complexes were synthesized in ethanol media by reacting Ni(O₂CCH₃)₂·4H₂O, H₂bhac and L in 1:1:1 mole ratio and characterized by analytical, magnetic and spectroscopic methods. X-ray crystal structures of both complexes have been determined. In each complex, the metal ion is in square-planar N₂O₂ coordination geometry. In the solid state, a one-dimensional assembly of the [Ni(bhac)(Himdz)] molecules is formed via intermolecular hydrogen bonds between the imidazole N–H groups and the uncoordinated N-atoms of the deprotonated amide functionalities. On the other hand, two [Ni(bhac)(Hdmpz)] molecules are involved in a pair of complementary hydrogen bonds between the pyrazole N–H groups and the coordinated O-atoms of the deprotonated amide functionalities forming a dinuclear species.     

Synthesis,crystal structures and urease inhibitory activity of copper(II) complexes with Schiff bases

Two thiocyanate-coordinated Schiff base copper(II) complexes, [CuL¹(NCS)] (1) and [Cu₂(L¹)₂(μ_1,3-NCS)₂]_n (2), where L¹ and L² are the deprotonated forms of 4-bromo-2-[(2-propylaminoethylimino)methyl]phenol (HL¹) and 2-ethoxy-6-[(2-propylaminoethylimino)methyl]phenol (HL²), respectively, have been prepared and structurally characterized. Single crystal X-ray diffraction indicates that 1 is a mononuclear copper(II) complex, while in 2, the adjacent two complex molecules are linked through two phenolate O atoms, forming a dimer. The dimers in 2 are further weakly linked through end-to-end thiocyanate bridges to form a two-dimensional sheet. The Cu atom in 1 is four-coordinate in a square planar geometry, and that in 2 is six-coordinate in an octahedral geometry. Complex 1 shows strong urease inhibitory activity, while complex 2 shows no activity.     

Syntheses and characterization of a chelating resin containing ONNO donor quadridentate Schiff base and its coordination complexes with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), cadmium(II), molybdenum(VI) and uranium(VI),

A new mixed Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine) has been synthesized by the condensation of equimolar quantities of ethylenediamine, salicylaldehyde and 3-formylsalicylic acid. A polymer supported Schiff base (PS–CH₂–LH₂) has been synthesized by the reaction of chloromethylated polystyrene (containing 3.9 mmol of chlorine per g of resin and 2% cross-linked with divinylbenzene) and the Schiff base N,N′-ethylenemono(3-carboxysalicylideneimine)mono(salicylideneimine). The polymer-anchored Schiff base reacts with metal salt/metal complex and forms polymer-anchored complexes having the formulae PS–CH₂–LCu, PS–CH₂–LNi, PS–CH₂–LCo, PS–CH₂–LFeCl·DMF, PS–CH₂–LZn, PS–CH₂–LCd, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂. The polymer-anchored complexes have been characterized on the basis of elemental analysis, infrared and electronic spectra and magnetic susceptibility measurements. The shifts of the ν(CN) (azomethine) stretch to lower energy and ν(CO) (carboxylic) to higher energy in the polymer-anchored complexes indicate the ONNO donor behaviour of the chelating resin. The metal ions in the metal bound polymers can be leached by hot dilute formic acid, acetic acid or hydrochloric acid. The coordinated dimethylformamide is completely lost on heating the complexes in air. The complexes PS–CH₂–LCu and PS–CH₂–LCo are paramagnetic with square planar structure, PS–CH₂–LNi is diamagnetic with square planar structure and PS–CH₂–LFeCl·DMF is paramagnetic and octahedral, PS–CH₂–LZn and PS–CH₂–LCd are diamagnetic and tetrahedral, PS–CH₂–LMoO₂ and PS–CH₂–LUO₂ are diamagnetic and have octahedral structure. The stoichiometry and the structure of the metal bound polymers are comparable with those of metal complexes of N,N′-ethylenebis(salicylideneimine). This is the first report of the syntheses of a mixed Schiff base and its coordination complexes.     

Synthesis,crystal structure and nonlinear optical property of cadmium(II) and copper(II) complexes with novel chiral ligand

Two novel metal-organic frameworks (MOFs) [Cd(3-MPCA)₂ · H₂O] · 5.5H₂O (1) and [Cu(3-MPCA)₂ · H₂O] · 4H₂O (2) [3-MPCA⁻ = (1R, 3S)-1,2,2-trimethyl-3-(pyridin-3-ylmethylcarbamoyl)cyclopentanecarboxylate] were hydrothermally synthesized and characterized by X-ray crystallography. Complexes 1 and 2 are homochiral and have similar one-dimensional (1D) chain structure, which are further linked by strong hydrogen bonds to give 3D architectures. There are oxygen hexmers and heptamers from water molecules and carbonyl group in 1 with O⋯O distances and O–O–O angles comparable to the corresponding values in ice. Nonlinear optical measurements on powdered sample of 1 and 2 revealed that they display second-harmonic-generation (SHG) response of 0.8 and 0.3 times of that for urea, respectively.     

含硫Schiff碱铜(Ⅱ)配合物的合成与表征

合成由水杨醛和1，3－二氨基硫脲缩合的含硫希夫碱配体及其铜（Ⅱ）配合物。化合物用元素分析、红外光谱、磁化率、摩尔电导等方法进行了表征。确定了它们的组成和可能的空间构型。     

New method in synthesis of nano uranyl(VI) Schiff base complexes: Characterization and electrochemical studies

This study presents a new method in synthesis of nano uranyl Schiff base complexes. In this method slow addition of dilute uranyl(VI) acetate solution to dilute Schiff base solution following the reflux for about 24 h, yields nano uranyl(VI) Schiff base complexes. Characterization of Schiff base ligands and nano uranyl complexes has been done using ¹H NMR, IR, UV–vis spectroscopy, elemental analysis. Schiff base ligands were synthesized by the condensation of one mole 3,4-diaminobenzophenone and two moles salicylaldehyde or substituted salicylaldehyde (3-OMe, 4-OMe, 5-OMe, 5-Br, 5-Cl). The electrochemical properties of the uranyl(IV) complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, according to the following trend: 5-MeO < H < 5-Br ≈ 5-Cl. Also the effect of the position of the substituted groups of Schiff base on the anodic potentials is as follows: 5-OMe < 3-OMe < 4-OMe.     

Synthesis and characterization of nickel(II) and copper(II) complexes with a tetramethyltetraaza macrocycle containing 2-pyridylmethyl pendant arms

The complexes [Ni(L²)](ClO₄)₂·H₂O (1) and [Cu(L²)]Cl₂·4H₂O (2) have been synthesized and characterized by X-ray crystallography, electronic absorption and cyclic voltammetry. The crystal structure of 1 reveals a distorted octahedral geometry with four nitrogen atoms of the macrocycle and two nitrogen atoms of the pendant pyridylmethyl groups. The structure of 2 shows that the complex is centrosymmetric and the metal center has a tetragonally distorted octahedral environment. The electronic spectra and electrochemical behaviors of the complexes are significantly affected by the presence of the pendant arms.     

Dicopper(I) and disilver(I) complexes of a thiophene-derived Schiff base macrocycle

Dicopper(I) and disilver(I) complexes of a tetraimine Schiff base macrocycle derived from the cyclocondensation of thiophene-2,5-dicarbaldehyde with 1,4,7-triazaheptane (1) have been synthesised and characterised. The structure of Cu₂(1)(BF₄)₂·2CH₃CN is given.     

One-pot template synthesis and crystal structure of two new polyaza copper(II) complexes

A new 14-membered hexazamacrocyclic copper(II) complex [Cu(H₂L¹)](ClO₄)₄(L¹=1,8-bis(2-aminoethyl)-1,3,6,8,10,13-hexaazacyclotetradecane) has been prepared by the one-pot reaction of ethylenediamine and formaldehyde in the presence of the Cu(II) ion. The crystal structure of [Cu(H₂L¹)](ClO₄)₄ was determined by X-ray diffraction. It crystallizes in the triclinic space group P−1 with a=12.118(2) Å, b=12.438(2) Å, c=12.466(2) Å, α=102.26(1)°, β=112.82(1)°, γ=111.51(1)°, and Z=2. The coordination geometry around the copper(II) ions is axially elongated octahedral with four nitrogen atoms of the macrocycle [Cu–N 2.012(7) Å for Cu(1) and 2.013(6) Å for Cu(2), average value] and two oxygen atoms of two ClO₄⁻ anions [Cu–O=2.550 Å for Cu(1) and 2.601(6) Å for Cu(2)]. [CuL²](ClO₄)₂(L²=3,7-bis(2-aminoethyl)-1,3,5,7-tetraazabicyclo[3,3,2]decane) with a novel tetraazabicyclic ligand was obtained from the same reaction system as an additional product. Crystal structure of [CuL²](ClO₄)₂: monoclinic space group Cc, a=16.393(3) Å, b=8.8640(18) Å, c= 13.085(3) Å, β=105.01(3)°, and Z=4.     

L-缬氨酸席夫碱金属配合物的合成及光催化性质

以L-缬氨酸和香兰素为起始原料,设计并合成了3种L-缬氨酸席夫碱金属配合物C_(13)H_(20)Fe~(2+)NO_6、C_(13)H_(20)Cu~(2+)NO_6和C_(13)H_(20)Sn~(2+)NO_6,采用1H NMR、MS(EI)和元素分析等表征其结构。以3种L-缬氨酸席夫碱金属配合物作为光催化剂,研究25℃下,C_(13)H_(20)Fe~(2+)NO_6、C13H20Cu2+NO6和C13H20Sn2+NO6催化剂在甲醇与水混合溶液中的亚甲基蓝降解性能。结果表明,3种催化剂对亚甲基蓝均有降解活性,其中,C13H20Sn2+NO6催化剂的亚甲基蓝降降解性能最好,预测这是一类潜在的环保性光催化材料。     

Correlation of spectral and redox properties of some mixed-ligand complexes of copper(II)

In aqueous potassium nitrate the complexes Cu(dip)(gly) Cl. 1.5 H₂O, Cu(dip)(alan) Cl. 1.5 H₂O, Cu(dip)(val) Cl.3 H₂O, Cu(dip)(ser) Cl H₂O have been observed to undergo single step two electron irreversible electroreduction at dme. From the characteristics of irreversible wave, the rate constant k_r for each complex has been calculated at reference potential −0.2142V vs sce. It is observed that the electroreduction of the complexes Cu(dip)(gly) Cl.1.5 H₂O, Cu(dip)(alan) Cl. 1.5H₂O does not follow a particular reaction mechanism with temperature. It has been also observed that the half-wave potential shifts towards more negative side as the ligand field band shifts to higher energy side. A correlation between electrode behaviour characteristics and spectral characteristics has been attempted. A possible electron transfer mechanism has been suggested on the basis of orientation of orbitals towards the electrode. The stability constant data obtained from the literature also support the proposed mechanism.     

In situ Cu(II)-containing chiral polymer complex sensor for enantioselective recognition of phenylglycinol

A chiral polymer P1 was synthesized by the polymerization of 2,5-dibutoxy-1,4-di(benzaldehyde)-1,4-diethynylbenzene (M-1) with (R,R)-1,2-diaminocyclohexane (M-2) via Schiff's base formation, and the chiral polymer P2 could be obtained by the reduction reaction of P1 with NaBH₄. P2 can serve as a “turn-off” fluorescent sensor toward Cu²⁺ and Ni²⁺. The in situ generated Cu(II)-containing polymer complex of P2 (Cu(II)-P2) can exhibit remarkable “turn-on” fluorescence enhancement response and considerable enantioselectivity toward unmodified phenylglycinol via a ligand displacement mechanism. More importantly, (R,R)-Cu(II)-P2 solution can turn on bright blue fluorescence color change again upon addition of l-phenylglycinol under a commercially available UV lamp, which can be clearly observed by the naked eyes for direct visual discrimination at low concentration. The simple, rapid and sensitive benign process makes this protocol promising for recognition of phenylglycinol enantiomers.     

Ruthenium catalyzed asymmetric transfer hydrogenation based on chiral P,N,O Schiff base ligands and crystal structure of a ruthenium(II) complex bearing chiral P,N,O Schiff base ligands

A ruthenium catalyst, generated in situ by heating the chiral P,N,O Schiff base ligand L (L = (S)-Ph₂PC₆H₄CNCHPhCH₂OH) with Ru(DMSO)₄Cl₂ in 2-propanol, is active for asymmetric transfer hydrogenation with best enantioselectivity up to 81%. A ruthenium complex of formula RuL₂Cl₂ is prepared and its crystal structure revealed that the two chiral P,N,O Schiff ligands are in meridional configuration. This complex is also an active catalyst for asymmetric transfer hydrogenation. However, the ‘[Ru(DMSO)₄]Cl₂ + chiral P,N,O ligand’ protocol displays better enantioselectivity.     

Adsorption of Cu(II) onto silica gel-immobilized Schiff base derivative

4-chloroisonitroacetophenone 4-aminobenzylhydrazone (CAAH) chemically anchored on a silica gel surface, has been used for Cu(II) sorption from aqueous solution. The surface modification processes was performed after silanization of silica, then analyzed by elemental analysis, infrared spectroscopy, and thermogravimetry. The sorption behavior of copper(II) was evaluated by the use of batch and column methods. The influences of the concentration, temperature and pH for sorption on the immobilized silica gel with Schiff base were investigated. The obtained dynamic data were fitted to Freundlich, Langmuir and Dubinin-Raduskevich (D-R) isotherms. The mean sorption energy (E) of copper sorption onto silica gel was calculated from D-R isotherm indicating a chemical ion-exchange. The thermodynamic parameters such as Gibbs free energy change, enthalpy change and entropy change were calculated from the adsorption isotherms which were used to explain the mechanism of the adsorption.