Fe(III) sequestering agents built on poly(ethylenimine) through crosslinkage of three molecules of a salicylate derivative preassembled by Fe(III) ion

Three molecules of 5-(bromoacetyl) salicylate ( 1 ) complexed to Fe(III) ion were crosslinked with poly(ethylenimine) (PEI) in DMSO by alkylation of amino groups of PEI with 1 , leading to the formation of Fe(Sal)₃PEI, a water-soluble polymer. Several other derivatives including the immobilized form were also prepared. Examination of the values of log K_f for the PEI derivatives indicated that each Fe(III) binding site in Fe(Sal)₃PEI contains three salicylate moieties. In addition, the log K_f revealed that the effective molarity (EM) of the salicylate groups contained in the Fe(III) binding site is ca. 1000M. The high EM value shows that the geometry of the coordination sphere is well conserved during the crosslinkage with PEI of 1 preassembled around Fe(III) ion. In view of the EM value and the pK_a values of salicylic phenols in apo(Sal)₃-PEI, the metal-free form, the three salicylate groups of each Fe(III) binding site appear to occupy proximal positions leading to effective cooperation in Fe(III) binding. Fast, strong, and selective binding of Fe(III) ion by the binding site comprising three salicylate moieties was demonstrated. In addition, rapid demetalation of the resulting complexes as well as chemical stability of the immobilized chelating agents built on PEI were achieved. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1197–1210, 1997     

Uranyl ion complexation of 2,2′-dihydroxyazobenzene enhanced on a backbone of poly(ethylenimine)

The formation constant (K_f) for the uranyl complex of 2,2′-dihydroxyazobenzene (DHAB) was measured with DHAB attached to poly(ethylenimine) (DHAB-PEI) at pH 7.7 to 9.4. The value of K_f was estimated from the equilibrium constant for extraction of uranyl ion from the uranyl complex of DHAB-PEI (UO₂DHAB-PEI) with carbonate ion, which in turn was measured from the absorbance change observed on addition of bicarbonate ion to the solution of UO₂DHAB-PEI. At pH 8.0, the uranyl-binding ability of DHAB was enhanced by about 10⁴ times on attachment of DHAB to PEI. The major origin of the increased ability of uranyl ion complexation is the basic local microenvironment of PEI, which encourages ionization of the phenol groups of DHAB. Various other possible origins are discussed also. The log K_f for DHAB-PEI at pH 8.0 indicates that DHAB moieties of DHAB-PEI are mostly occupied, whereas DHAB unattached to PEI is mostly unoccupied by uranyl ion under conditions of seawater when only the pH and concentrations of bicarbonate and uranyl ions of seawater are considered. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3936–3942, 1999     

Self-optimization of binding sites by Ni(II) ion on carboxypyrazine-containing poly(ethylenimine)

To test the concept of self-optimization of own binding site by a metal ion, host molecules for Ni(II) ion were built on poly(ethylenimine) (PEI) by using the ethylenediamine portions of PEI and 2-carboxypyrazinyl (CP) group. Two derivatives of PEI containing CP were prepared: one by random acylation of PEI with pyrazine-2,5-dicarboxylic acid mono-(2,5-dioxo-pyrrolidin-1-yl) ester (PC-DP), and the other by acylation of PEI with PC–DP in the presence of Ni(II) ion. Between these two CP derivatives of PEI, Ni(II) binding ability was more than 10³ times greater for the latter. Optimization by Ni(II) ion of its own binding site built on the polymer was attributed to the preassemblage of PC–DP and PEI with Ni(II) ion and the subsequent attack at PC–DP by an amino group of PEI located in an optimal position. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 533–537, 1997.     

Equilibrium constant for coordinative polymerization of an o,o′-dihydroxyazobenzene derivative with Ni(II) ion in water

Equilibrium constant (K_CP) for coordinative polymerization is measured for the first time. Constant K_CP is defined as [L]_cp/[M][L], where [L]_cp represents the concentration of the ligand present in the coordination polymer. Plot of absorbance changes measured for 3, a water-soluble derivative of o,o′-dihydroxyazobenzene, against the concentration of Ni(II) ion indicates formation of a 1 : 1-type complex in water at pH 7.74 and 25°C when Ni (II) is added in excess of 3. The 1 : 1-type complex can be either Ni 3, the monomeric complex, or (Ni 3 )_n, the coordination polymer. The equilibrium constant for formation of the 1 : 1-type complex is estimated as 10^13.10 by using UO₂²⁺ ion as the competing metal ion. For the Ni(II) complex of an o,o′-dihydroxyazobenzene derivative attached to poly(ethylenimine), the formation constant is estimated as 10^5.36. Due to the structure of the polymer, possibility of coordinative polymerization is excluded for the polymer-based ligand. The much greater equilibrium constant for formation of the Ni(II) complex of 3, therefore, indicates formation of (Ni 3 )_n instead of Ni 3. The value of K_CP for (Ni 3 )_n shows that only 10⁻⁷% of the initially added 3 is left unpolymerized when Ni(II) is added in excess of 3 by 10⁻⁴ M. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 1825–1830, 1997     

Complexation of poly(ethyleneimine) with copper(II) and nickel(II) ions in 0.5 M KNO3 solution

Complexation of poly(ethyleneimine) (PEI) with copper(II) and nickel(II) ions was studied in a 0.5M aqueous KNO₃ solution. The potentiometrically determined logarithm of the three successive formation constants (log k_J) were 8.14, 7.96, and 7.37 for Cu⁺²-PEI complexation and 6.74, 6.52, and 6.23 for Ni⁺²–PEI complexation at 25°C, according to Bjerrum's modified method. The maximum average coordination number was 3.2 for the Cu⁺²–PEI system and 3.7 for the Ni⁺²–PEI system. An entropy effect was observed in the third coordination. The wavelengths of maximum absorption of the complexes and the continuous variation method showed that at least two coordination sites of Cu⁺² ion and three coordination sites of Ni⁺² ion were occupied immediately by PEI as the solutions of PEI and the metal ions were mixed.     

Synthesis,characterization, and polychelatogenic properties of poly(acrylic acid-co-acrylamide)

The radical copolymerization of acrylic acid with acrylamide was carried out at different monomer ratios in solution (DMF) at 60°C. The corresponding homopolymers were also synthesized to compare their metal ion binding abilities. All the copolymers were characterized by elemental analysis. The metal ion binding properties of these water-soluble polymers with Cu(II), Co(II), Ni(II), Cd(II), Zn(II), Pb(II), Hg(II), Fe(III), and Cr(III) ions were investigated in aqueous solution using the Liquid-Phase Polymer-Based Retention (LPR) technique. Poly(acrylic acid-co-acrylamide) showed a higher retention compared to the homopolymers for all the metal ions except of Hg(II), which was not retained. Besides, the retention of Cd(II) is higher than that an addition of the retention of both homopolymers. It may be attributed to a synergic effect. Maximum capacity for Cu(II) at pH 5.0 was determined to be 1 mmol g⁻¹ (63.5 mg g⁻¹). © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35 : 2461–2467, 1997     

Hydrophobic Effects of o-Phenanthroline and 2,2′-Bipyridine on Adsorption of Metal(II) Ions onto Silica Gel Surface

The effects of o-phenanthroline and 2,2′-bipyridine on the adsorption of metal(II) (Fe, Co, Ni and Cu) ions onto silica gel surface have been studied. The adsorption is expressed in terms of the measured concentrations of both metal and ligand at equilibrium. Each adsorption of the four metal ions is increased with the presence of the ligands. In addition, adsorption increases slowly with pH at low pH values and then increases rapidly up to near the pK_a value of silica gel (≈6.5). The adsorption of each metal ion at low pH is increased with increased ligand concentration. However, at high pH the adsorptions of Fe(II) and Cu(II) are decreased with increased ligand concentration whereas the adsorptions of Co(II) and Ni(II) are always increased. At low pH values the ligand to metal ratio adsorbed on the silica gel surface is ca. 3:1 while at high pH values it is 1:1, 2:1, and 3:1, corresponding to the initial ligand to metal ion concentration ratio. The addition of ethanol to the phenanthroline-SiO₂ solution results in a decrease in the adsorption of phenanthroline. The effect of ethanol is also observed in the Fe(II)-phenanthroline-SiO₂ system. The behavior of the adsorption is interpreted qualitatively by hydrophobic expulsion, the formation of surface complexes, and electrostatic interaction. It is concluded that hydrophobic expulsion plays an important role in the adsorption of metal ions in the presence of hydrophobic ligands on silica gel surface.     

Synthesis, Structure, Magnetism and Electrochemical Properties of Linear Pentanuclear Complex: Ni5(μ-dmpzda)4(NCS)2

吡啶修饰的线性五核金属化合物[Ni5(μ-dmpzda)4(NCS)2][ dmpzda-H2=N,N’-Di(4-methyl pyrydin-2-yl)pyrazine-2,6-diamine]被合成并表征,其电化学和磁性被报告。 化合物含有接近180º的 Ni-Ni-Ni角,末端含有两个轴配体的Ni5 线性链。这个五核线性金属链被四个顺式的dmpzda2-配体螺旋包裹。化合物中存在两种类型的Ni-Ni键长：末端连接有轴配体的Ni-Ni键长被配体影响,其键长为2.3821 Å;内部的Ni-Ni距离比较短,为2.2959 Å。两末端的Ni(II)离子由于连接轴配体构成四方锥形(NiN4NCS)并存在较长的Ni-N 键长（2.103 Å),这个键长符合高自旋Ni(II)构型。内部的三个Ni-N 距离为1.886-1.906 Å,这样构成正方形平面(NiN4)并呈低自旋的顺磁构型。化合物显示了同[Ni5(μ-tpda)4(NCS)2]类似的磁性,即在化合物中两末端Ni(II)仍存在反铁磁性的作用。     

Poly(N‐phenylmaleimide‐co‐acrylic acid)–copper(II) and poly(N‐phenylmaleimide‐co‐acrylic acid)–cobalt(II) complexes: Synthesis,characterization, and thermal behavior

The free‐radical copolymerization of N‐phenylmaleimide (N‐PhMI) with acrylic acid was studied in the range of 25–75 mol % in the feed. The interactions of these copolymers with Cu(II) and Co(II) ions were investigated as a function of the pH and copolymer composition by the use of the ultrafiltration technique. The maximum retention capacity of the copolymers for Co(II) and Cu(II) ions varied from 200 to 250 mg/g and from 210 to 300 mg/g, respectively. The copolymers and polymer–metal complexes of divalent transition‐metal ions were characterized by elemental analysis, Fourier transform infrared, ¹H NMR spectroscopy, and cyclic voltammetry. The thermal behavior was investigated with differential scanning calorimetry (DSC) and thermogravimetry (TG). The TG and DSC measurements showed an increase in the glass‐transition temperature (T_g) and the thermal stability with an increase in the N‐PhMI concentration in the copolymers. T_g of poly(N‐PhMI‐co‐AA) with copolymer composition 46.5:53.5 mol % was found at 251 °C, and it decreased when the complexes of Co(II) and Cu(II) at pHs 3–7 were formed. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4933–4941, 2005     

Poly(propylene imine) dendrimer complexes of Cu(II), Zn(II), and Co(III) as catalysts of hydrolysis of p-nitrophenyl diphenyl phosphate

Poly(propylene imine) dendrimers having 8, 32, and 64 primary amine end groups form diamino Cu(II), diamino Zn(II), and tetramino Co(III) complexes that are identified spectrophotometrically and titrimetrically. The dendrimer–metal ion complexes catalyze the hydrolysis of p-nitrophenyl diphenyl phosphate in zwitterionic buffer solutions at pH ≤ 8.1 with relative activities Cu(II) > Zn(II) > Co(III). The rates of hydrolysis are faster with sodium perchlorate than with sodium chloride to control ionic strength. In sodium perchlorate solutions with Cu(II) the rates increase with increasing size of the dendrimer. In sodium chloride solutions with Cu(II) the rates decrease with increasing size of the dendrimer. Rate constants in buffered sodium chloride solutions of dendrimers and 1.0mM Cu(II) are 1.3–6.3 times faster than in the absence of Cu(II). The fastest hydrolyses occurred at a dendrimer primary amine to Cu(II) ratio NH₂/Cu ≤ 2. At NH₂/Cu = 4 and with the 1,4,7,10-tetraazacyclodecane complex of Cu(II) hydrolysis rates were much slower. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 2727–2736, 1999     

Structurally characterized homotrinuclear Salamo‐type nickel(II) complexes: Synthesis,solvent effect and fluorescence properties

Four new solvent‐induced Ni(II) complexes with chemical formulae [{NiL(μ₂‐OAc)(MeOH)}₂Ni]·2MeOH ( 1 ), [{NiL(μ₂‐OAc)}₂(n‐PrOH)(H₂O)Ni]·n‐PrOH ( 2 ), [{NiL(μ₂‐OAc)(DMF)}₂Ni] ( 3 ) and [{NiL(μ₂‐OAc)(DMSO)}₂Ni]·2DMSO ( 4 ), (H₂L = 4‐Nitro‐4′‐chloro‐2,2′‐[(1,3‐propylene)dioxybis(nitrilomethylidyne)]diphenol) have been synthesized and characterized by elemental analyses, FT‐IR, UV–Vis spectra and X‐ray crystallography. X‐ray crystal structure determinations revealed that each of the Ni(II) complexes 1–4 consists of three Ni(II) atoms, two completely deprotonated (L)^2? units, two μ₂‐acetate ions and two coordinated solvent molecules (solvents are methanol, n‐propanol, water, N,N‐dimethylformamide and dimethyl sulphoxide, respectively). Although the four complexes 1–4 were synthesized in different solvents, it is worthwhile that the Ni(II) atoms in the four complexes 1–4 adopt hexa–coordinated with slightly distorted octahedral coordination geometries, and the ratios of the ligand H₂L to Ni(II) atoms are all 2: 3. The complexes 1–4 possess self‐assembled infinite 1D, 3D, 1D and 2D supramolecular structures via the intermolecular hydrogen bonds, respectively. In addition, fluorescence behaviors were investigated in the complexes 1–4 .     

Vitrification/devitrification phenomena during isothermal and nonisothermal crystallization of poly(aryl–ether–ether–ketone) (PEEK) and PEEK/poly(ether–imide) blends

We have established time–temperature transformation and continuous-heating transformation diagrams for poly(ether–ether–ketone) (PEEK) and PEEK/poly(ether–imide) (PEI) blends, in order to analyze the effects of relaxation control on crystallization. Similar diagrams are widely used in the field of thermosetting resins. Upon crystallization, the glass transition temperature (T_g) of PEEK and PEEK/PEI blends is found to increase significantly. In the case of PEEK, the shift of the α-relaxation is due to the progressive constraining of amorphous regions by nearby crystals. This phenomenon results in the isothermal vitrification of PEEK during its latest crystallization stages for crystallization temperatures near the initial T_g of PEEK. However, vitrification/devitrification effects are found to be of minor importance for anisothermal crystallization, above 0.1°C/min heating rate. In the case of PEEK/PEI blends, amorphous regions are progressively enriched in PEI upon PEEK crystallization. This promotes a shift of the α-relaxation of these regions to higher temperatures, with a consequent vitrification of the material when crystallized below the T_g of PEI. The data obtained for the blends in anisothermal regimes allow one to detect a region in the (temperature/heating rate) plane where crystallization proceeds in the continuously close proximity of the glass transition (dynamic vitrification). These experimental findings are in agreement with simple simulations based on a modified Avrami model coupled with the Fox equation. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 919–930, 1998     

Synthesis and structural characterization of new trinuclear cobalt(II) and nickel(II) complexes possessing five- and six-coordinated geometry

Tri-nuclear cobalt and nickel complexes ([(CoL)₂(OAc)₂Co]?·?THF (I) and [(NiL)₂(OAc)₂(THF)₂Ni]?·?THF (II)) have been synthesized by reaction of a new Salen-type bisoxime chelating ligand of 2,2′-[ethylenedioxybis(nitrilomethylidyne)]dinaphthol(H₂L) with cobalt(II) acetate tetrahydrate or nickel(II) acetate tetrahydrate, respectively. Complexes I and II were characterized by elemental analyses, IR, TG-DTA and ¹H-NMR etc. The X-ray crystal structures of I and II reveal that two acetate ions coordinate to three cobalt or nickel ions through M–O–C–O–M (M?=?Co or Ni) bridges and four μ-naphthoxo oxygen atoms from two [ML] units also coordinate to cobalt(II) or nickel(II). Complex I has two distorted square-pyramidal coordination spheres and an octahedral geometry around Co1. In complex II all three nickel ions are six-coordinate.     

Ni(II) ion-imprinted solid-phase extraction and preconcentration in aqueous solutions by packed-bed columns

Solid-phase extraction (SPE) columns packed with materials based on molecularly imprinted polymers (MIPs) were used to develop selective separation and preconcentration for Ni(II) ion from aqueous solutions. SPE is more rapid, simple and economical method than the traditional liquid-liquid extraction. MIPs were used as column sorbent to increase the grade of selectivity in SPE columns. In this study, we have developed a polymer obtained by imprinting with Ni(II) ion as a ion-imprinted SPE sorbent. For this purpose, NI(II)-methacryloylhistidinedihydrate (MAH/Ni(II)) complex monomer was synthesized and polymerized with cross-linking ethyleneglycoldimethacrylate to obtain [poly(EGDMA-MAH/Ni(II))]. Then, Ni(II) ions were removed from the polymer getting Ni(II) ion-imprinted sorbent. The MIP-SPE preconcentration procedure showed a linear calibration curve within concentration range from 0.3 to 25 ng/ml and the detection limit was 0.3 ng/ml (3 s) for flame atomic absorption spectrometry (FAAS). Ni(II) ion-imprinted microbeads can be used several times without considerable loss of adsorption capacity. When the adsorption capacity of nickel imprinted microbeads were compared with non-imprinted microbeads, nickel imprinted microbeads have higher adsorption capacity. The K_d (distribution coefficient) values for the Ni(II)-imprinted microbeads show increase in K_d for Ni(II) with respect to both K_d values of Zn(II), Cu(II) and Co(II) ions and non-imprinted polymer. During that time K_d decreases for Zn(II), Cu(II) and Co(II) ions and the k′ (relative selectivity coefficient) values which are greater than 1 for imprinted microbeads of Ni(II)/Cu(II), Ni(II)/Zn(II) and Ni(II)/Co(II) are 57.3, 53.9, and 17.3, respectively. Determination of Ni(II) ion in sea water showed that the interfering matrix had been almost removed during preconcentration. The column was good enough for Ni determination in matrixes containing similar ionic radii ions such as Cu(II), Zn(II) and Co(II).     

Spectral and thermal studies of new Co(II) and Ni(II) hexaaza and octaaza macrocyclic complexes

The macrocyclic complexes of Co(II) and Ni(II) having chloride or thiocyanate ions in the axial position have been synthesized and characterized. These complexes are synthesised by the template condensation of o-phenylenediamine or 2,3-butanedionedihydrazone with the appropriate aldehydes in NH₄OH solution in the presence of the metal ions, Co(II) and Ni(II). The complexes were characterized by spectroscopic methods (IR, UV-Vis and ESR) and magnetic measurements as well as thermal analysis (TG and DTA). The results obtained are commensurate with the proposed formulae. Spectral studies indicate that these complexes have an octahedral structure. From conductivity measurements the complexes are non-electrolytes. The kinetic of the thermal decomposition of the complexes was studied and the thermodynamic parameters are reported.     

Binding of uranyl ion by 2,2′-dihydroxyazobenzene attached to crosslinked polystyrenes covered with highly populated quaternary ammonium cations

2,2′-Dihydroxyazobenzene (DHAB) derivatives were attached to poly(chloromethylstyrene-co-divinylbenzene) (PCD) because of the high affinity of DHAB for uranyl ion. Chloromethyl groups of PCD were converted to quaternary ammonium ions by treating them with tertiary amines. Two strategies were adopted to improve the uranyl-binding ability of the immobilized DHAB: (1) the creation of a highly cationic microenvironment around the DHAB moieties and (2) the introduction of electron-withdrawing groups to DHAB. Capacity of the resins for uranyl uptake was measured, revealing that about 10 to 46 mg of uranium could be complexed to 1 g of the resins. Formation constants (K_f) for the uranyl complexes of the resins were determined. In the presence of ≥0.02 M bicarbonate ion at pH 8.02, log K_f values of 14.3 to 15.8 were obtained. Uranium extraction from seawater with two kinds of resins prepared in this study was carried out on the east coast of the Korean peninsula. The amount of uranium extracted from seawater was up to 150 μg/g resin. Thus, the uranium-extracting capability of the DHAB-containing polystyrene resins was improved significantly by the structural modifications. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 4117–4125, 1999     

Factors driving the protonation of poly(N-vinylimidazole) hydrogels

Poly(N-vinylimidazole) hydrogels immersed in aqueous acid solutions produce an increment in the pH of the bath because of proton uptake by basic imidazole moieties, leading to hydrogel protonation. Both kinetic and equilibrium measurements of the pH of the bath have been performed under a variety of conditions and with different hydrogel samples. The kinetics of the xerogel protonation process (which includes solvent and titrant diffusion, the true protonation reaction or ion–dipole association, and the polymer relaxation to a new conformation) are mostly driven by the size of the hydrogel sample, whereas other magnitudes, such as the initial pH, the effective polymer concentration, and the network structure, governed by the crosslinker ratio and total comonomer concentration in the feeding, have a minor influence. pK_a changes with the degree of protonation (α), delimitating two different regions: (1) a broad α range in which pK_a decreases with increasing α but less pronouncedly with increasing ionic strength and (2) an α range close to α = 1 in which pK_a decreases abruptly, more markedly with sulfate than with chloride counteranions and with larger ionic strengths. In the first region, pK_a is determined by repulsive electrostatic interactions and so is larger for titration with H₂SO₄ than with HCl and increases as the effective polymer concentration and ionic strength increase. Two steps (i.e., two protonation sites) can be observed in the titration curves, the second one corresponding to abrupt changes in the basicity of the second pK_a-versus-α region. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2294–2307, 2004     

Nickel(II) and copper(II) complexes of aza macrocycles derived from trichloromethane

Syntheses of nickel(II) complexes of the tetraaza macrocycles 2,7-dichloro-1,3,6,8-tetraazacyclodecane (DCCD) and 2,8-dichloro-1,3,7,9-tetraazacyclododecane (DICD) and a copper(II) complex of 2,6,8,12,13,17-hexaazabicyclo[5.5.5]heptadecane (HBCH) are reported in the template condensation of trichloromethane with 1,2-diaminoethane or 1,3-diaminopropane. Formulation of the synthesized products [Ni(DCCD)(H₂O)₂]Cl₂, [Ni(DICD)(H₂O)₂]Cl₂?·?H₂O, and [Cu₃(HBCH)(H₂O)₆]Cl₆, and the metal-free ligand hydrochloride HBCH?·?6HCl has been confirmed by elemental analyses, conductivity measurements, and spectral studies. Potentiometric studies of nickel(II) and copper(II) complexes of HBCH and structurally similar 2,5,8,10,13,16,17,20,23-nonaazabicyclo[7.7.7]tricosane (NACT, earlier derived from trichloromethane and diethylenetriamine) have also been performed in the structural support of HBCH. In 1?:?1, metal?:?HBCH solution, copper(II) is coordinated to four N-donors of two-HN(CH₂)₃NH– groups of the ligand in a non-planar tetraaza cavity. The equilibrium constant value (log?K?=?15.41) for the reaction Cu^2+?+?A???CuA²⁺ (A?=?HBCH) is in favor of the cyclic structure of the ligand. A high value (log?K?=?23.27) for corresponding reaction in the NACT system is due to conformational change in the ligand, where copper(II) organizes the macrocycle to form a nearly planar cavity in which the cation fits well.     

Synthesis,structure, spectroscopic,and DNA binding properties of Co(III) and Ni(II) complexes with ((E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile)

Two new complexes, [Co(L)₂]Cl·(MeOH)₂ (1) and [Ni(L)₂]₄·EtOH (2) (L?=?(E)-2-(amino((pyridin-2-ylmethylene)amino)methylene)maleonitrile), were synthesized and characterized by X-ray crystallography, IR, UV, and fluorescence spectroscopy. According to X-ray crystallographic studies, each metal was six-coordinate with six nitrogens from two ligands. Both complexes form two-dimensional supramolecular networks via hydrogen bonding and π–π interactions. Ultraviolet and visible spectra showed that absorptions arise from π–π ^?, MLCT, and d–d electron transitions. Fluorescence spectroscopy revealed moderate intercalative binding of these two complexes with EB–DNA, with apparent binding constant (K _app) values of 9.14?×?10⁵ and 3.20?×?10^5?M^?1 for Co(III) and Ni(II) complexes, respectively. UV–visible absorption spectra showed that the absorption of DNA at 260?nm was quenched for 2 but quenched then improved for 1 with addition of complexes, tentatively attributed to the effect of the combined intercalative binding and electrostatic interaction for 1.     

Synthesis and Complexation of 1,2-Bis[(monoaza[15]crown-5)-N-yl]glyoxime. Crystal Structure of (1,2-Bis[(monoaza[15]crown-5)-N-yl]glyoximato)palladium(II)

A new vicinal dioxime ligand with two crown-ether groups, 1,2-bis[(monoaza[15]crown-5)-N-Yl]-glyoxime(LH₂), has been prepared from cyanogen di-N-oxide and monoaza[15]crown-5. Ni(II), Pd(II), and Pt(IV) complexes of LH₂ with or without alkali-metal ions bound to macrocyclic groups have been isolated. The high affinity of [Pd(LH)₂] and [Ni(LH)₂] for the K⁺ ion is observed in solvent extraction experiments. A single-crystal X-ray structure confirms the postulated geometry of [Pd(LH)₂]- The Pd-atom of the centro-symmetric molecule has square-planar PdN₄ coordination where Pd–N distances range from 1.978(3) to 1.970(3) Å. The N–Pd–N intraligand angle is 79.9(1)^°.