Salophen Complex Research Articles

Double-receptor sandwich supramolecule sensing method for the determination of ATP based on uranyl–salophen complex and aptamer

In this study, we report a double-receptor sandwich supramolecule sensing method for the determination of adenosine triphosphate (ATP). One receptor is a uranyl–salophen complex which can bind the triphosphate group in ATP selectively, and another is an anti-adenosine aptamer which is a single-stranded oligonucleotide and can recognize the adenosine group in ATP specifically. The uranyl–salophen complex was immobilized on the surface of amino-silica gel particles and used as the solid phase receptor of ATP. The anti-adenosine aptamer was labeled with a fluorescent group and used as the labeled receptor of ATP. In the procedure of ATP detection, ATP was first combined with the solid phase receptor and then conjugated with the labeled receptor to form a sandwich-type supramolecule. The conditions of fabricating solid phase receptor and the influence of manifold variables on the determination were studied. The experimental results demonstrate that the method has a number of advantages such as high selectivity, high sensitivity, good stability and low cost. Under optimal conditions, the linear range for detection of ATP is 0.2–5.0nmol/mL with a detection limit of 0.037nmol/mL. The proposed method was successfully applied for the determination of ATP in real samples with the recoveries of 96.8–103.3%.

Electrical-field-induced structural change and charge transfer of lanthanide–salophen complexes assembled on carbon nanotube field effect transistor devices

The application of a negative gate voltage on a carbon nanotube field effect transistor decorated by a binuclear Tb(III) complex leads to the generation of a negatively charged mononuclear one, presenting an electron density transfer to the nanotube and ambipolar behaviour.

One‐Electron Oxidized Copper(II) Salophen Complexes: Phenoxyl versus Diiminobenzene Radical Species

Where is the radical? The π-system of the diiminobenzene bridge adds a putative oxidation site to prophenoxyl copper(II) salophen complexes. It is shown that the bridge is effectively redox active and that the radical site (phenoxyl vs. diiminobenzene bridge) in the above cations is tuned by selective methoxy substitution (see figure).

Electrochemical determinations of 6-mercaptopurine on the surface of a carbon nanotube-paste electrode modified with a cobalt salophen complex

A mixture of multi-walled carbon nanotube/graphite paste electrode modified with a salophen complex of cobalt was prepared and was applied for the study of the electrochemical behavior of 6-mercaptopurine (MP) using cyclic and differential pulse voltammetry (DPV). An excellent electrocatalytic activity toward the oxidation of MP was achieved, which led to a considerable lowering in the anodic overpotential and remarkable increase in the response sensitivity in comparison with unmodified electrode. Utilizing DPV method, a linear dynamic range of 1–100 μM with detection limit of 0.1 μM was obtained in phosphate buffer of pH 3.0. The electrochemical detection system was very stable, and the reproducibility of the electrode response, based on the six measurements during 1 month, was less than 3.0% for the slope of the calibration curves of MP. The electrochemical method as a simple, sensitive, and selective method was developed for the determination of MP in pharmaceutical dosage form and human plasma without any treatments.

Kinetics of demetallation of a zinc–salophen complex into liposomes

A Zn–salophen complex has been incorporated into POPC large unilamellar liposomes (LUV) obtained in phosphate buffer at pH 7.4. Fluorescence optical microscopy and anisotropy measurements show that the complex is located at the liposomal surface, close to the polar headgroups. The interaction of the POPC phosphate group with Zn2+ slowly leads to demetallation of the complex. The process follows first order kinetics and rate constants have been measured fluorimetrically in pure water and in buffered aqueous solution.The coordination of the phosphate group of monomeric POPC with salophen zinc also occurs in chloroform as detected by ESI-MS measurements.The effect of the Zn–salophen complex on the stability of POPC LUV has been evaluated at 25°C by measuring the rate of release of entrapped 5(6)-carboxyfluorescein (CF) in the presence and in the absence of Triton X-100 as the perturbing agent. It turns out that the inclusion of the complex significantly increases the stability of POPC LUV.

ChemInform Abstract: Coupling Reaction of Acid Chlorides with Terminal Alkynes Catalyzed by Diatomite‐Supported Palladium(II) Salophen Complex.

ChemInform Abstract: Coupling Reaction of Acid Chlorides with Terminal Alkynes Catalyzed by Diatomite‐Supported Palladium(II) Salophen Complex.

ChemInform Abstract: The First Heterogeneous Sonogashira Coupling Reaction of Aryl Halides with Terminal Alkynes Catalyzed by Diatomite‐Supported Palladium(II) Salophen Complex.

AbstractThe new catalyst is air‐stable and can be reused at least 5 times without any decrease in activity.

Oxovanadium(IV) salophen complex covalently anchored to multi-wall carbon nanotubes (MWNTs) as heterogeneous catalyst for oxidation of cyclooctene

The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, hydroxyl functionalized oxovanadium(IV) Schiff-base; ( N, N-bis(4-hydroxysalicylidene)phenylene-1,2-diamine)oxovanadium(IV), [VO((OH) 2-salophen)]; has been covalently anchored on modified MWNTs. The new modified MWNTs ([VO((OH) 2-salophen)]@MWNTs]) have been characterized by transmission electron microscopy (TEM), atomic absorption spectroscopic (AAS) analysis, X-ray diffraction (XRD), Diffuse reflectance (DRS) UV–vis, FT-IR spectroscopy and elemental analysis. The analytical data indicated a composition corresponding to the mononuclear complex of tetradentate Schiff-base ligand. The characterization of the data showed the absence of extraneous complex, retention of MWNTs and covalently anchored on modified MWNTs. Liquid-phase oxidation of cyclooctene with molecular oxygen to a mixture of cyclooctene-1-one, cyclooctene-1-ol and cyclooctene epoxide in CH 3CN have been reported using oxovanadium(IV) Schiff-base complex covalently anchored on modified MWNTs as catalysts.

Coupling Reaction of Acid Chlorides with Terminal Alkynes Catalyzed by Diatomite-Supported Palladium(II) Salophen Complex

Coupling Reaction of Acid Chlorides with Terminal Alkynes Catalyzed by Diatomite-Supported Palladium(II) Salophen Complex

The first heterogeneous Sonogashira coupling reaction of aryl halides with terminal alkynes catalyzed by diatomite‐supported palladium(II) salophen complex

AbstractWe report here our observation that, using appropriate reaction conditions, the Sonogashira reaction can be performed without the need for copper catalyst and solvent. Our approach involves the use of diatomite‐supported palladium(II) salophen complex as a catalyst and triethylamine as a base. The methodology works, to differing extents, for aryl iodides and bromides. This heterogeneous catalyst can be reused at least five times without any decrease in activity. Copyright © 2011 John Wiley & Sons, Ltd.

Spectrophotometric Study on the Binding of Two Water Soluble Schiff Base Complexes of Mn (III) with ct-DNA

In this work, binding of two water soluble Schiff base complexes: Bis sodium (5-sulfosalicylaldehyde) o-phenylendiiminato) Manganese (III) acetate (Salophen complex) and Bis sodium (5-sulfosalicylaldehyde) 1, 2 ethylendiiminato) Manganese (III) acetate (Salen complex) with calf thymus (ct) DNA were investigated by using different spectroscopic and electrometric techniques including UV-vis, Circular dichroism (CD) and fluorescence spectroscopy, viscommetry and cyclic voltammetry (CV). Both complexes have shown a hyperchromic and a small bathochromic shift in the visible region spectra. A competitive binding study showed that the enhanced emission intensity of ethidium bromide (EB) in the presence of DNA was quenched by the addition of the two Schiff base complexes indicating that they displace EB from its binding site in DNA. Moreover structural changes in the CD spectra and an increase in the CV spectra with addition of DNA were observed. The results show that both complexes bind to DNA. The binding constants have been calculated using fluorescence data for two complexes also K(b) was calculated with fluorescence Scatchard plot for Salophen. Ultimately, the experimental results show that the dominant interactions are electrostatic while binding mode is surface binding then followed by hydrophobic interactions in grooves in high concentration of complexes.

Two- and three-dimensional packing diagrams of M(salophen) complexes

For better understanding of two- (2D) and three-dimensional (3D) crystal engineering of metal complexes, the 2D and 3D packing diagrams of metal salophen (=N,N′-o-phenylene-bis(salicylideneimine)) complexes are compared in detail. According to the 3D structures, determined by X-ray crystallography, N,N′-(o-phenylene)bis(4-hexyloxysalicylideneiminato)Cu(II) (1) and N,N′-(o-phenylene)bis(4-decyloxysalicylidene-iminato)Ni(II) (2) have a square-planar coordination geometry. 1 forms a host–guest complex with CH2Cl2 solvent molecule via intermolecular hydrogen bonds. In 2 the interdigitating alkyl chains allow the molecules to be packed in parallel sheets with a zigzag-type pattern while in 1 the molecules are packed in coplanar layers. In both structures the layers are connected by short {M}⋯H contacts (3.07 A in 1, 3.15 A in 2). The molecular packings in planes of the 3D structures are compared with previously determined 2D surface patterns of five equivalent Cu(II), Ni(II) and Co(II) complexes formed at the liquid–solid interface. The structures were studied at the interface by means of scanning tunneling microscopy. It is shown that in the case of 2 the 2D structures observed in the plane of a bulk crystal and at the liquid–solid interface are not comparable. As shown, even the metal ion and the alkyl chain length affect differently on the 2D and 3D packing. The role of molecular planarity on the packing diagrams is addressed by comparing the nearly planar single crystal structures of salophen complexes 1 and 2 to the structure of N,N′-ethylene-bis(4-octyloxysalicylideneiminato)Cu(II) which has a twisted salen moiety.

ChemInform Abstract: Metal—Salophen‐Based Receptors for Anions

AbstractReview: 112 refs.

Non-Centrosymmetric Tetrameric Assemblies of Tetramethylammonium Halides with Uranyl Salophen Complexes in the Solid State

Ditopic salophen-UO(2) receptors 1-4 and 7 co-crystallize with tetramethylammonium (TMA) chloride and fluoride salts producing good quality crystals amenable for X-ray diffraction characterization. The arrangement of the receptor and salt units in the crystal lattice is such that tetrameric ball-shaped assemblies are formed, where an inner cluster of four TMA cations are surrounded by an outer shell of four UO(2)-bound anions. These elaborate architectures, which occur in all cases, regardless of a certain degree of structural modification on the receptors, lead to lattices that belong to non-centrosymmetric (NCS) space groups. Interestingly, the tetragonal symmetry of the tetrameric ball-shaped assemblies is either retained (I4̅) or lost (R3c and I4̅3d) at the lattice level, without compromising the NCS nature of the crystal lattices. The principal X-ray investigation on TMAX (X = Cl/F) co-crystals, that is, 1-(TMA)Cl, 2-(TMA)Cl, 3-(TMA)Cl, 4-(TMA)Cl, 7-(TMA)Cl, and 7-(TMA)F, is accompanied by NMR and electrospray ionization (ESI) mass spectrometry studies to gather additional insight on the modality of formation of the solid state structures observed. The important role of cation-π interactions in the receptor-salt recognition process is renewed and strengthened by comparison with NMR titration data with a novel reference compound, the salophen-UO(2) complex 8. Given the importance of NCS and polar crystalline solids in the development of functional materials, this study shows that this property can be introduced into elaborate host-guest systems, as those which assemble in the architectures described here, thus expanding its field of applicability.

Catalytic oxidation of primary aromatic amines with sodium periodate catalyzed by Mn(III)salophen complex supported on polystyrene-bound imidazole

The catalytic activity of Mn(III)salophen complex supported on polystyrene-bound imidazole, [Mn(salophen)Cl-PSI], was studied in the oxidation of primary aromatic amines in acetonitrile/water, using sodium periodate as an oxygen source. Amines were oxidized efficiently to their corresponding azo derivatives in the presence of this catalyst. The heterogeneous catalyst showed high stability and reusability in the oxidation reactions and could be reused several times without loss of its activity. The effect of different solvents was studied in the oxidation of p-toluidine and CH3CN/H2O was chosen as the solvent.

Specific Supramolecular Interactions between Zn2+-Salophen Complexes and Biologically Relevant Anions

Recognition of inorganic phosphates PO(4)(3-), P(2)O(7)(4-), and P(3)O(10)(5-) and nucleotides AMP(2-), ADP(3-), and ATP(4-) by Zn(2+)-salophen complexes 1 and 2 in ethanol was investigated by different spectroscopic techniques. (31)P NMR and mass spectrometry showed that anions of both series are bound by 1 and 2, while absorption and emission studies revealed that only nucleotides produce relevant changes in the spectral properties of the two hosts. (1)H NMR studies proved that the adenine aromatic group is involved in the complexation, thus pointing out the role of supramolecular ditopic receptors played by salophen derivatives toward this class of biologically relevant substrates. The lifetime of the photogenerated triplet state of the Zn(2+)-salophen compounds was measured by nanosecond laser flash photolysis, and the observed changes upon increasing the concentration of nucleotides allowed the identification of the formation of a 1:0.5 host/guest intermediate complex additionally to the formation of a 1:1 complex.

A study of the electrocatalytic oxidation of methanol on a nickel–salophen-modified glassy carbon electrode

Nickel–salophen-modified glassy carbon electrodes prepared by transferring one drop of Ni–salophen complex solution on the electrode surface. This modified electrode has been used for the electrocatalytic oxidation of methanol in alkaline solutions with various methods such as cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The electrooxidation was observed as large anodic peaks, and early stages of the cathodic direction of potential sweep around 20 mV vs. Ag|AgCl|KClsat. A mechanism based on the electrochemical generation of Ni (Ш) active sites and their subsequent consumptions by methanol have been discussed. EIS studies were employed to unveil the charge transfer rate as well as the electrical characteristics of the catalytic surface. For the electrochemical oxidation of methanol at 5.0 M concentration, charge transfer resistance of nearly 0.936 kΩ was obtained, while the resistance of the electrocatalyst layer was about 111.6 Ω.

Cobalt salophen complex immobilized into montmorillonite as catalyst for the epoxidation of cyclohexene by air

Cobalt salophen (N, N′-bis (salicylidene)o-phenylenediamine) complex was immobilized in the montmorillonite. The montmorillonite was characterised by atomic absorption spectroscopic (AAS) analysis, Fourier transform infrared (FT-IR), diffuse reflectance UV–vis, powder-X-ray-diffraction (PXRD) and X-ray photoelectron spectroscopy (XPS) measurements. The catalytic activity of the novel cobalt salophen based materials was tested in the epoxidation of cyclohexene in the isobutyraldehyde/air system using acetonitrile as solvent and very high TOF value (10.1 min − 1 ) was obtained. Various reaction conditions were studied. The experimental results indicated very good catalytic activity and selectivity in the epoxidation of cyclohexene. Repeated runs of the catalysts were carried out five times and the results indicated that the catalyst was stable for the epoxidation of cyclohexene.

Polymeric Membrane Electrodes with High Nitrite Selectivity Based on Rhodium(III) Porphyrins and Salophens as Ionophores

Several porphyrin and salophen complexes with Rh(III) are examined as ionophores to prepare nitrite selective polymeric membrane electrodes. All ionophores tested exhibit preferred selectivity toward nitrite anion. Enhanced potentiometric nitrite selectivity is observed in the presence of either lipophilic anionic as well as cationic sites within the membranes, suggesting that the ionophores can function via either a charged or a neutral carrier response mechanism. Among a range of complexes and membrane formulations examined, optimal nitrite selectivity and reversible response down to 5 x 10(-6) M is achieved using Rh(III)-tetra(t-butylphenylporphyrin) as the ionophore in the presence of lipophilic cationic sites in plasticized poly(vinyl chloride) membrane. Response times are substantially longer than typical membrane electrodes apparently because of a slow nitrite ligation reaction with Rh(III); however, a significant improvement in dynamic EMF response can be realized by optimizing the membrane formulation and increasing the temperature. The selectivity observed with these membranes is greater than the best nitrite selective electrodes reported to date in the literature based on lipophilic Co(III)-corrin complexes, allowing the new nitrite electrodes to be utilized to determine the level of nitrite in meats with good correlation to the colorimetric Griess assay method.

Enantiomerization of Chiral Uranyl−Salophen Complexes via Unprecedented Ligand Hemilability: Toward Configurationally Stable Derivatives

In the search for configurationally stable inherently chiral uranyl-salophen complexes, the newly synthesized compound 3 featuring a dodecamethylene chain was expected to be a promising candidate. Unexpectedly, dynamic HPLC on a enantioselective column showed that it still undergoes enantiomerization at high temperature. By comparison with the dynamic behavior of compounds 4 and 5, it was found that the enantiomerization rate is independent of the size of the ligand. This finding definitely rules out a jump rope-type mechanism for the enantiomerization process and points to reaction pathways involving preliminary rupture of one of the O...U coordinative bonds. This provides unprecedented evidence of the occurrence of ligand hemilability in metal-sal(oph)en complexes. Such findings inspired the synthesis of compound 6 endowed with a more rigid spacer, i.e., that derived from 4,4'-(1,4-phenylenediisopropylidene)bisphenol. DHPLC investigations showed that the new structural motif imparts a higher configurational stability, thus raising the half-life for the enantiomerization to more than 2 months at room temperature. This clearly establishes that this compound represents the first member of a new class of inherently chiral receptors, whose potential in chiral recognition and catalysis now can be feasibly explored.