Complexation of 4′-nitrobenzo-15-crown-5 with Mg<Superscript>2+</Superscript>, Ca<Superscript>2+</Superscript>, Sr<Superscript>2+</Superscript> and Ba<Superscript>2+</Superscript> metal cations in acetonitrile-methanol binary solutions

The complex formation reactions between Mg²⁺, Ca²⁺, Sr²⁺ and Ba²⁺ metal cations with macrocyclic ligand, 4′-nitrobenzo-15C5, were studied in acetonitrile (AN)-methanol (MeOH) binary mixtures at different temperatures using conductometric method. The results show that 4′-nitrobenzo-15C5 forms 1:1 [ML] complexes with Mg²⁺, Ca²⁺ and Sr²⁺ metal cations in solutions. But in the case of Ba²⁺ cation a 1:2 [ML₂] complex is formed in these solvent systems. The stability of the complexes is sensitive to the solvent composition and a non-linear behavior was observed for variation of logK _f of the complexes versus the composition of the binary mixed solvents. The stability constants of complexes decrease suddenly with increasing the concentration of methanol in this binary system. The values of thermodynamic parameters (ΔH _c^° and ΔS _c^°) for formation of (4′-nitrobenzo-15C5.Mg)²⁺, (4′-nitrobenzo-15C5.Ca)²⁺ and (4′-nitrobenzo-15C5.Sr)²⁺ complexes were obtained from temperature dependence of the stability constants and the results show that these parameters are affected by the nature and composition of the mixed solvents. A non-linear behavior is observed between the ΔS _c^° and the composition of the mixed solvents.     

Synthesis,Crystal Structure and Properties of Two Macrocyclic Dinuclear Complexes

Two macrocyclic dinuclear complexes, [Cu₂L¹](PF₆)₂ and [Cu₂L²](ClO₄)₂, were synthesized by cyclo-condensation between N,N′-bis(3-formyl-5-methylsalicylidene)ethylenediimine or N,N′- bis(3-formyl-5-n-butylsalicylidene)ethylenediimine and ethylenediamine in the presence of Cu²⁺ ions. The crystal structures of the complexes were studied. The variable-temperature magnetic susceptibilities and cyclic voltammograms of the complexes were measured. The magnetic and electrochemical properties of the complexes were discussed. The results show that the complexes display very strong antiferromagnetic exchanges and that all copper(II) complexes undergo a one-electron transfer process.     

Copper(II) complexing with 2′,2′-diethylheptanohydrazide

Acid-base properties of 2′,2′-diethylheptanohydrazide (DEHH) and its complex formation with copper(II) ions in water-isopropanol solutions were studied. Cationic complexes with [Cu²⁺] : [DEHH] ratios of 1 : 1 and 1 : 2 were found to be formed in weak acid media, and an uncharged complex with a [Cu²⁺] : [DEHH] ratio of 1 : 2 was found to be formed in a basic medium. log K _st values were determined. The data obtained were compared with the stability constants of copper(II) 2′,2′-diethylbenzohydrazide complexes.     

Coordination compounds of sodium,potassium, and calcium with benzo-15-crown-5-substituted terpyridines

Sodium and potassium complexes with 4′-(4‴-benzo-15-crown-5)methyloxy-2,2′:6′,2″-terpyridine (L¹) and 4′-(4′-benzo-15-crown-5)oxy-2,2′:6′,2″-terpyridine (L²) and heteronuclear Na, K, Ca, and transition metal complexes with L¹ were synthesized. The structure of the complexes was proposed on the basis of elemental analysis data, IR spectra, and the results of earlier X-ray diffraction studies of L², [NaL¹NCS], and [Na₂{Cu(L¹)₂}(NCS)₃]NCS · CH₃CN.     

A kinetic investigation into the rate of chloride substitution from chloro terpyridine platinum(II) and analogous complexes by a series of azole nucleophiles

The substitution kinetics of the complexes [Pt(terpy)Cl]Cl·2H₂O (PtL1), [Pt(^tBu₃terpy)Cl]ClO₄ (PtL2), [Pt{4′-(2′′′-CH₃-Ph)terpy}Cl]BF₄ (PtL3), [Pt{4′-(2′′′-CF₃-Ph)terpy}Cl]CF₃SO₃ (PtL4), [Pt{4′-(2′′′-CF₃-Ph)-6-Ph-bipy}Cl] (PtL5) and [Pt{4′-(2′′′-CH₃-Ph)-6-2′′-pyrazinyl-2,2′-bipy}Cl]CF₃SO₃ (PtL6) with the nucleophiles imidazole (Im), 1-methylimidazole (MIm), 1,2-dimethylimidazole (DIm), pyrazole (Pyz) and 1,2,4-triazole (Trz) were investigated in a methanolic solution of constant ionic strength. Substitution of the chloride ligand from the metal complexes by the nucleophiles was investigated as a function of nucleophile concentration and temperature under pseudo first-order conditions using UV/Visible and stopped-flow spectrophotometric techniques. The reactions follow the rate law k_\textobs = k₂ [ \textNu ] + k _{- 2} k_{\text{obs}} = k_{2} \left[ {\text{Nu}} \right] + k_{ - 2} . The results indicate that changing the nature or distance of influence of the substituents on the terpy moiety affects the π-back-donation ability of the chelate. This in turn controls the electrophilicity of the metal centre and hence its reactivity. Electron-donating groups decrease the reactivity of the metal centre, while electron-withdrawing groups increase the reactivity. Placing a strong σ-donor cis to the leaving group greatly decreases the reactivity of the complex, while the addition of a good π-acceptor group significantly enhances the reactivity. The results indicate that the metal is activated differently by changing the surrounding atoms even though they are part of a conjugated system. It is also evident that substituents in the cis position activate the metal centre differently to those in the trans position. The kinetic results are supported by DFT calculations, which show that the metal centre is less electrophilic when a strong σ-donor is cis to the leaving group and more electrophilic when a good π-acceptor group is part of the ring moiety. The temperature dependence studies support an associative mode of activation. An X-ray crystal structure of Pyz bound to PtL3 was obtained and confirmed the results of the DFT calculations as to the preferred N-atom as a binding site.     

Synthesis and characterization of new <Emphasis Type="Italic">vic</Emphasis>-dioximes and their metal complexes with Cu(II), Ni(II), and Co(II) salts

4-Acetyldiphenyl sulfide and 4,4′-diacetyldiphenyl sulfide were synthesized from diphenyl sulfide and acetyl chloride in the presence of AlCl₃ as catalyst in the Friedel-Crafts reaction. Subsequently, the ketooxime and glyoxime derivatives were also prepared. The metal complexes of the glyoximes, such as copper, nickel, and cobalt complexes were prepared. The BF²⁺ capped Ni(II) mononuclear complex of 4-thiophenoxyphenylglyoxime was prepared. The structures of these ligands were identified by FT-IR, ¹H NMR, and ¹³C NMR spectral data and elemental analysis. The structures of the complexes were identified by FT-IR, elemental analysis, and magnetic measurements. The text was submitted by the authors in English.     

Molecular structure and character of bonding of mono and divalent metal cations (Li+, Na+, K+, Mg2+, Ca2+, Zn2+, and Cu+) with guanosine: AIM and NBO analysis

The B3LYP/6-311++G (d,p) density functional approach was used to study the gas-phase metal affinities of Guanosine (ribonucleoside) for the Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Zn²⁺, and Cu⁺ cations. In this study we determine coordination geometries, binding strength, absolute metal ion affinities, and free energies for the most stable products. We have also compared the results for Guanosine, with our previously reported results for 2′-Deoxyguanosine. Based on the results, it is obvious that MIA is strongly dependent on the charge-to-size ratio of the cation. Guanosine interacts more strongly with Zn²⁺ than do with Mg²⁺, Ca²⁺, and Cu⁺ and therefore stronger interactions lead to higher MIA. In both free molecules and their complexes, the Syn orientation of the base is stabilized by an intramolecular O5′–H···N3 hydrogen bond and the anti orientation of the base is stabilized by an intramolecular C–H···O hydrogen bond formed between the (C8-H8) and the O5′ atom of the sugar moiety. It is also interesting to mention that linear correlation between calculated MIA values and the atomic numbers (Z) of the metal ions of Li⁺, Na⁺, and K⁺ were found. Furthermore, the influences of metal cationization on the strength of the N-glycosidic bond, torsion angles, angle of pseudorotation (P), and intramolecular C–H···O and O–H···O hydrogen bonds have been studied. Natural bond orbital (NBO) analysis was performed to calculate the charge transfer and natural population analysis of the complexes. Quantum theory of atoms in molecules (QTAIM) was also applied to determine the nature of interactions.     

Effect of non-aqueous solvents on stoichiometry and selectivity of complexes formed between 4′-nitrobenzo-15-crown-5 with Fe3+, Y3+, Cd2+, Sn4+, Ce3+ and Au3+ metal cations

The complexation processes between Fe³⁺, Y³⁺, Cd²⁺, Sn⁴⁺, Ce³⁺ and Au³⁺ metal cations with macrocyclic ligand, 4′-nitrobenzo-15-crown-5 (4′NB15C5), were studied in acetonitrile (AN), methanol (MeOH) and nitromethane (NM) solvents at different temperatures using conductometric method. The conductance data show that the stoichiometry of the complexes formed between this macrocyclic ligand and Cd²⁺, Au³⁺ cations is 1: 1 (ML), but in the case of Fe³⁺, Y³⁺ and Ce³⁺ metal cations, 2: 1 (M₂: L) and 2: 2 [M₂: L₂] complexes are formed in nitromethane solutions. The results show, that the selectivity of 4’NB15C5 for the studied metal cations in methanol solutions at 15°C is: Sn⁴⁺ > Cd²⁺ > Y³⁺ > Fe³⁺ ∼ Ce³⁺ > Au³⁺, but in the case of acetonitrile, the stability order was found to be: Y³⁺ > Au³⁺ > Fe³⁺ > Cd²⁺. The values of stability constants of the 1: 1 [M: L] complexes were determined from conductometric data using a GENPLOT computer program. The values of thermodynamic parameter (ΔH _c ^o and ΔH _c ^o) for formation of the complexes were obtained from temperature dependence of the stability constants, using the van’t Hoff plots. The results show that the values of standard enthalpy (ΔH _c ^o) and standard entropy (ΔH _c ^o) change with the nature of the non aqueous solvents.     

Complexation of 4′-Nitrobenzo-15-crown-5 with Zn<Superscript>2+</Superscript>, Mn<Superscript>2+</Superscript>, Cr<Superscript>3+</Superscript> and Sn<Superscript>4+</Superscript> Cations in Acetonitrile–Ethanol Binary Mixtures

The complexation reactions of 4′-nitrobenzo-15-crown-5 (4′NB15C5) with Zn²⁺, Mn²⁺, Cr³⁺ and Sn⁴⁺ cations were studied in acetonitrile–ethanol (AN–EtOH) binary solvent mixtures at different temperatures by the electrical conductometry method. The stability constants of the resulting 1:1 complexes were determined from computer fitting of the conductance versus mole ratio data. The results show that the selectivity order of 4′NB15C5 for the metal cations in the AN–EtOH (mol-%AN=76) binary solvent at 298.15 K is: Cr³⁺>Mn²⁺≈Zn²⁺>Sn⁴⁺, but the selectivity order changes with the composition of the mixed solvents. A nonlinear relationship was observed between the stability constants (log ₁₀ K _f) of these complexes and the composition of the AN–EtOH binary solvents. The corresponding thermodynamic parameters (DH_c^o, DS_c^o)(\Delta H_{\mathrm{c}}^{\mathrm{o}}, \Delta S_{\mathrm{c}}^{\mathrm{o}}) were obtained from the temperature dependence of the stability constants using van’t Hoff plots. The results show that the values and also the sign of these parameters are influenced by the nature and composition of the mixed solvents.     

Synthesis,DNA-binding and photocleavage studies of cobalt(III) complexes [Co(bpy)<Subscript>2</Subscript>(dpta)]<Superscript>3+</Superscript> and [Co(bpy)<Subscript>2</Subscript>(amtp)]<Superscript>3+</Superscript>

Two novel cobalt(III) mixed-polypyridyl complexes [Co(bpy)₂(dpta)]³⁺ and [Co(bpy)₂(amtp)]³⁺ (bpy = 2,2′-bipyridine, dpta = dipyrido-[3,2-a;2′,3′-c]-thien-[3,4-c]azine, amtp = 3-amino-1,2,4-triazino[5,6-f]-1,10-phenanthroline) have been synthesized and characterized. The interaction of Co^III complexes with calf thymus DNA was investigated by spectroscopic and viscosity measurements. Results suggest that the two complexes bind to DNA via an intercalative mode. Moreover, Co^III complexes have been found to promote the photocleavage of plasmid DNA pBR322 under irradiation at 365 nm. The mechanism studies reveal that hydroxyl radical (OH^•) is likely to be the reactive species responsible for the cleavage of plasmid DNA by [Co(bpy)₂(dpta)]³⁺ and superoxide anion radical (O ₂ ^•− ) acts as the key role in the cleavage reaction of plasmid DNA by [Co(bpy)₂(amtp)]³⁺.     

Spectroscopic and thermal investigations of complexes of Cr<Superscript>III</Superscript>, Mn<Superscript>II</Superscript>, Zn<Superscript>II</Superscript> &; Cd<Superscript>II</Superscript> - carboxamide

Complexes of Cr^III, Mn^II, Zn^II & Cd^II with the polydentate carboxamide ligandN′, N′′-bis(3-carboxy-1-oxoprop-2-enyl) 2-Amino-N-arylbenzamidine (H₂L) have been synthesized and characterized by elemental analyses, spectroscopic studies (Vibrational, electronic, ESR and ¹H-NMR), magnetic susceptibility measurements, thermal studies and powder diffraction studies. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicates octahedral or tetrahedral geometry around the metal ions, has been supported by magnetic susceptibility measurements. The results of electron spin resonance & ¹H-NMR spectra have supported the results of other spectral techniques. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. Powder diffraction determines the cell parameters of the complexes.     

Synthesis and magnetic properties of complexes of a conjugated hyperbranched polymer containing bithiazole rings

A novel conjugated hyperbranched polymer containing bithiazole rings（PBTADB） was synthesized by polycondensation of 1,3,5-benzenetricarboxaldehyde and 2,2’-diamino-4,4’-bithiazole（DABT）.The structure of the hyperbranched polymer was confirmed by FT-IR and ¹H-NMR.PBTADB dissolved in organic polar solvents such as DMSO and NMP.Bithiazole rings were introduced to provide bidentate N-donor sites for binding metal ions.The metal complexes were prepared by chelation of the polymer with Co²⁺ and Sm³⁺.The magnetic behavior of coordination compounds was measured as a function of magnetic field strength（0-4.8×10⁶ A/m） at 5 K and as a function of temperature（5-300 K） at magnetic field strength of 2.4×10⁶ A/m.The magnetic hysteresis loops of PBTADB-Sm³⁺and PBTADB-Co²⁺showed the typical ’S’ shape at 5 K with the Curie-Weiss temperature T_θ=96 K and 41 K respectively.The results show that they exhibit properties of soft ferromagnetic materials.     

Studies on the Synthesis and Thermodynamic Stability of Two Multidentate Ligands 2,9-disubstituted 1,10-phenanthroline

Two multidentate ligands: N,N′-di-(propionic acid-2′-yl-)-2,9-di-aminomethylphenanthroline (L₁) and N,N′-di-(3′-methylbutyric acid-2′-yl-)-2,9-di-amino-methylphenanthroline (L₂) were synthesized and fully characterized by ¹H NMR and elemental analysis. The binding ability of L₁ and L₂ to metal ions such as M(II) (M = Cu, Zn, Co and Ni) and Ln(III) (Ln = La, Nd, Sm, Eu, and Gd) has been investigated by potentiometric titration in aqueous solution and 0.1 mol dm⁻³KNO₃ at 25.0 ± °C. In view of the structure of L₁ and L₂, mononuclear metal complexes can be formed in solution. The stability constants of binary complexes of ligands L1 and L2 with metal ions M(II) and Ln(III) have been determined respectively and further discussed.     

Synthesis,DNA interaction and photocleavage studies of ruthenium(II) complexes with 2-(pyrrole) imidazo[4,5-f]-1,10-phenanthroline as an intercalative ligand

Three Ru(II) complexes, namely [Ru(bipy)₂PRIP]²⁺ (1), [Ru(dmb)₂PRIP]²⁺ (2), and [Ru(phen)₂PRIP]²⁺ (3) (dmb = 4,4′-dimethyl-2,2′-bipyridine; PRIP = 2-(pyrrole) imidazo [4,5-f]-1,10-phenanthroline) have been synthesized and characterized by elemental analysis, mass spectra, IR, ¹H NMR and ¹³C NMR. The DNA-binding properties of the three complexes with calf-thymus DNA (CT-DNA) were investigated by spectrophotometry, fluorescence methods and viscosity measurements. The results suggest that all three complexes bind to CT-DNA through intercalation. Also, when irradiated at 365 nm, the three complexes promote the photocleavage of plasmid pBR-322 DNA. Under comparable experimental conditions, complex 3 cleaves DNA more effectively than complexes 1 and 2.     

Synthesis and magnetic properties of poly(p‐phthaloyl‐disacetylaceton‐ethylenediimine) metal complexes

Macrocyclic Schiff‐base ligand, bisacetylaceton‐ethylenediimine (BAE) and its transition metal complexes M(BAE) (M = Cu²⁺, Ni²⁺) were synthesized. The complexes having characteristics of aromatic systems and well‐defined one‐dimensional structures, reacted with p‐phthaloyl chloride, to obtain polymer complexes. The complexes were characterized by elemental analysis, inductively coupled plasma (ICP), FT‐IR, and thermal analysis and show good thermal stability. ESR spectra analysis discovered that there are free radicals in the chain of polymers, indicating that a weak magnetic spin‐exchange interaction operates between the metal ions and free radicals. It is found that, as the bridging p‐phthaloyl group is able to propagate the magnetic exchange interaction, the polymer complexes show paramagnetic properties by measurement of temperature dependence of the magnetic property, and obey Curie–Weiss law. Copyright © 2001 John Wiley & Sons, Ltd.     

Synthesis of iminooxime derivatives and investigation of their complexes

Three novel ligands, a-pycolyliminoisonitrosoacetophenone (L¹H · HCl), α-pycolylimino-p-methylisonitrosoacetophenone (L²H · HCl), and a-pycolylimino-p-chloroisonitrosoacetophenone L³H, were synthesized. Their metal complexes with Co(II), Cu(II), and Ni(II) were prepared. The mononuclear complexes of these ligands with Co²⁺, Cu²⁺, and Ni²⁺ ions were obtained in ethanol. The structures of the ligands and their complexes were characterized by 1H NMR, IR spectroscopy, elemental analyses, and magnetic susceptibility. The text was submitted by the authrs in English.     

Fluorescence sensor using a molecularly imprinted polymer as a recognition receptor for the detection of aluminium ions in aqueous media

This paper describes the investigation of a molecularly imprinted polymer (MIP) as a sensing receptor for Al³⁺ ion detection by using an optical approach. Al³⁺ ion was adopted as the template molecule and 8-hydroxyquinoline sulfonic acid ligand as the fluorescence tag. The polymer was synthesised using acrylamide as monomer, 2-hydroxyethyl methacrylate as co-monomer and ethylene glycol dimethracylate as cross-linker. The free radical polymerisation was performed in methanol and initiated by 2,2′-azobisisobutyronitrile at 70 °C. The imprinted polymer was fluorometrically characterised using a fibre optic attachment in a self-designed flow-cell. NaF was used to leach the Al³⁺ ion from the MIP. The optimum pH for the rebinding of Al³⁺ ion with the leached polymer was found to be pH 5 and the fluorescence response was found to be stable within the buffer strength range of 0.05–0.10 M. The fluorescence intensity during Al³⁺ ion rebinding was inversely dependent on temperature, and a low interference response (<3%) toward metal ions except for Cu²⁺ and Zn²⁺ ions was observed. The polymer rebinding repeatability study conducted over 9 cycles with Al³⁺ ion (0.8×10⁻⁴ M) was found to give an RSD value of 2.82% with a standard deviation of 0.53. The dynamic range of the system was found to be linear up to 1.0×10⁻⁴ M Al³⁺ ion with a limit of detection of 3.62 μM.     

Thermal, spectral and magnetic characterization of Co(II), Ni(II) AND Cu(II) 4-chloro-2-nitrobenzoates

Physico-chemical properties of 4-chloro-2-nitrobenzoates of Co(II), Ni(II), and Cu(II) were studied. The complexes were obtained as mono- and trihydrates with a metal ion to ligand ratio of 1:2. All analysed 4-chloro-2-nitrobenzoates are polycrystalline compounds with colours depending on the central ions: pink for Co(II), green for Ni(II), and blue for Cu(II) complexes. Their thermal decomposition was studied only in the range of 293–523 K, because it was found that on heating in air above 523 K 4-chloro-2-nitrobenzoates decompose explosively. Hydrated complexes lose crystallization water molecules in one step and anhydrous compounds are formed. The final products of their decomposition are the oxides of the respective transition metals. From the results it appears that during dehydration process no transformation of nitro group to nitrite takes place. The solubilities of analysed complexes in water at 293 K are of the order of 10^–4–10^–2 mol dm^–3. The magnetic moment values of Co²⁺, Ni²⁺ and Cu²⁺ ions in 4-chloro-2-nitrobenzoates experimentally determined at 76–303 K change from 3.89 to 4.82 μ_B for Co(II) complex, from 2.25 to 2.98 μ_B for Ni(II) 4-chloro-2-nitrobenzoate, and from 0.27 to 1.44 μ_B for Cu(II) complex. 4-chloro-2-nitrobenzoates of Co(II), and Ni(II) follow the Curie–Weiss law. Complex of Cu(II) forms dimer.     

Role of mononuclear rare earth metal complexes in promoting the hydrolysis of p-nitrophenyl phosphate (NPP)

Two long-chain multidentate ligands: 2,9-di-(n-2′,5′,8′-triazanonyl)-1,10-phenanthroline (L₁) and 2,9-di-(n-4′,7′,10′-triazaundecyl)-1,10-phenanthroline (L₂) were synthesized. The hydrolytic kinetics of p-nitrophenyl phosphate (NPP) catalyzed by complexes of L₁ and L₂ with La(III) and Gd(III) have been studied in aqueous solution at 298 K, I = 0.10 mol · dm⁻³ KNO₃ at pH 7.5–9.1, respectively. The study shows that the catalytic effect of GdL1 was the best in the four complexes for hydrolysis of NPP. Its k_LnLH−1, k _LnL and pK _a are 0.0127 mol⁻¹ dm³ s⁻¹, 0.000022 mol⁻¹ dm³ s⁻¹ and 8.90, respectively. This paper expounds the result from the structure of the ligands and the properties of the metal ions, and deduces the catalysis mechanism.     

Hydrothermal synthesis of a 2-(2-pyridyl)imidazole derivative and its copper(II) and zinc(II) complexes

The hydrothermal synthesis of a heterocyclic quaternary nitrogen compound, namely, 6,7-dihydro-pyrido[2′,1′:3,4]pyrazino[1,2-a]imidazol-5-ium-bromide monohydrate (LBr · H₂O) is reported. Various spectroscopic analyses were performed on the cationic heterocycle. Cu^II and Zn^II halide complexes of this novel ligand were prepared. The heterocycle and its complexes were characterized by single crystal X-ray diffraction analysis. Both complexes contain neutral [M^IILX₃] molecules, where the cyclic ligand (L⁺) is coordinated to the metal as a monodentate ligand. The Cu²⁺ complex has a distorted tetrahedral geometry, indicating an obvious steric effect from L⁺ on the chloride co-ligand. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.