Functional microporous materials of metal carboxylate: Gas-occlusion properties and catalytic activities

Copper(II) terephthalate is the first transition metal complex found capable of adsorbing gases. This complex has opened the new field of adsorbent complex chemistry. It is recognized as the lead complex in the construction of microporous complexes. This specific system has been expanded to a systematic series of derivatives of other isomorphous transition metals, molybdenum(II), ruthenium(II, III), and rhodium(II). These complexes with open frameworks are widely recognized as very useful materials for applications to catalysis, separation at molecular level, and gas storage.     

Oral administration of Bis(aspirinato)zinc(II) complex ameliorates hyperglycemia and metabolic syndrome-like disorders in spontaneously diabetic KK-A(y) mice: structure-activity relationship on zinc-salicylate complexes

In recent years, the number of patients suffering from diseases, such as cancer, apoplexy, osteoporosis, hypertension, and type 2 diabetes mellitus is increasing worldwide. Type 2 diabetes, a lifestyle-related disease, is recognized as a serious disease. Various types of pharmaceutics for diabetes have been used. Since the relationship between diabetes and biometals such as vanadium, copper, and zinc ions has been recognized for many years, we have been developing the anti-diabetic metal complexes as new candidates. We found that several zinc(II) (Zn) complexes exhibit glucose-lowering activity for treating type 2 diabetes. High doses of salicylates have been known to reverse hyperglycemia and hyperinsulinemia in type 2 diabetic patients. These findings strongly suggest that the combined use of Zn and salicylates achieves the synergism in treating type 2 diabetes. Because aspirin, acetyl salicylic acid, has a chelating ability, we used it as a ligand to Zn. Several Zn-salicylate complexes were prepared and their biological activities were examined in this study. The complexes with an electron-withdrawing group in the ligand exhibited higher in vitro insulinomimetic activity than those of Zn complexes with an electron-donating group in the ligand. When bis(aspirinato)Zn (Zn(asp)?) complex was orally administered on KK-A(y) mice with hereditary type 2 diabetes, the diabetic state was improved. In addition, this complex exhibited normalizing effects on serum adiponectin level and high blood pressure in metabolic syndrome. In conclusion, Zn(asp)? complex is newly proposed as a potent anti-diabetic and anti-metabolic syndrome agent.     

Novel Synthesis of Cu-Schiff Base Complex@Metal-Organic Framework MIL-101 via a Mild Method: A Comparative Study for Rapid Catalytic Effects

The use of metal complex immobilized/decorated porous materials as catalysts has found various applications. As such, finding a new and mild method for synthesis of metal complex immobilized over porous material is of great interest. Immobilized porous materials for styrene oxidation were reported in this work. Immobilized porous material of Cu-Schiff base complex @MIL-101 were described, in which immobilized Cu-Schiff base complex within super cage of a metal-organic framework (MOF)-based porous material, chromium (III) terephthalate MIL-101. They were systematically characterized by using elemental analysis, powder X-ray diffraction, fourier transform infrared spectroscopy, N₂ absorption-desorption, and so on, also used as catalyst for the selective oxidation of styrene to benzaldehyde. Comparatively, the immobilized heterogeneous catalyst of Cu-Schiff base complex@MIL-101 acted as an efficient heterostructure catalyst in the oxidation of styrene to benzaldehyde up to six cycles, and showed superior activity for styrene oxidation over MIL-101.     

Synthesis, magnetic, spectral, and antimicrobial studies of Cu(II), Ni(II) Co(II), Fe(III), and UO2(II) complexes of a new Schiff base hydrazone derived from 7-chloro-4-hydrazinoquinoline

A new hydrazone ligand, HL, was prepared by the reaction of 7-chloro-4-hydrazinoquinoline with o-hydroxybenzaldehyde. The ligand behaves as monoprotic bidentate. This was accounted for as the ligand contains a phenolic group and its hydrogen atom is reluctant to be replaced by a metal ion. The ligand reacted with Cu(II), Ni(II), Co(II), Fe(III), and UO2(II) ions to yield mononuclear complexes. In the case of Fe(III) ion two complexes, mono- and binuclear complexes, were obtained in the absence and presence of LiOH, respectively. Also, mixed ligand complexes were obtained from the reaction of the metal cations Cu(II), Ni(II) and Fe(III) with the ligand (HL) and 8-hydroxyquinoline (8-OHqu) in the presence of LiOH, in the molar ratio 1:1:1:1. It is clear that 8-OHqu behaves as monoprotic bidentate ligand in such mixed ligand complexes. The ligand, HL, and its metal complexes were characterized by elemental analyses, IR, UV-vis, mass, and 1H NMR spectra, as well as magnetic moment, conductance measurements, and thermal analyses. All complexes have octahedral configurations except Cu(II) complex which has an extra square-planar geometry, while Ni(II) mixed complex has also formed a tetrahedral configuration and UO2(II) complex which formed a favorable pentagonal biprymidial geometry. Magnetic moment of the binuclear Fe(III) complex is quite low compared to calculated value for two iron ions complex and thus shows antiferromagnetic interactions between the two adjacent ferric ions. The HL and metal complexes were tested against one stain Gram positive bacteria (Staphylococcus aureus), Gram negative bacteria (Escherichia coli), and fungi (Candida albicans). The tested compounds exhibited higher antibacterial acivities.     

Catalysis of the silica sol-gel process by divalent transition metal bis(acetylacetonate) complexes

Transition metal bis(acetylacetonate) complexes of Co(II), Ni(II), Cu(II), and Zn(II) have been found to be active catalysts for the sol-gel process. The catalytic activity of these complexes decreases in going from Co(II) to Zn(II) and is highest for the acetylacetonate ligand system. 29Si NMR studies show that the complexes act primarily as condensation catalysts and are, in that regard, similar to Br?nsted bases such as hydroxide. Mechanistically, however, they appear to differ significantly from hydroxide in how they induce condensation. This is revealed in the catalyst concentration dependence, which is 1/2 order for the metal complexes and 1st order in hydroxide. Differences are also apparent in the thermochemical parameters that indicate that the metal complexes act to increase the entropy of the transition state leading to condensation. The catalytic activity is proportional to the degree of ligand dissociation of the metal complex, and experiments suggest that the active catalytic species is specifically the first dissociation product, MII(acac)+.     

Synthesis of innovative biochemical active mixed ligand metal(II) complexes with thiazole containing Schiff base: In vitro antimicrobial profile

An unique Schiff base ligand, formed by the condensation reaction of 2‐aminobenzothiazole with curcumin and its Cu(II), Ni(II), Co(II) and Zn(II) complexes incorporating 2,2′‐bipyridine as coligand were synthesised. They were characterized via analytical and spectroscopic methods. The complexes adopt square planar geometry. Their antimicrobial activity and photocatalytic efficiency on Congo red dye molecule were explored. It is found that all the complexes are antimicrobial active and show higher activity than the ligand. The nuclease activity of the above metal complexes was also assessed by absorption titration, fluorescence, viscosity and gel electrophoresis assay. The complexes bind CT DNA through intercalation mode. The data reveal that the above synthesised metal(II) complexes are found to be effective metallonucleases. The gel electrophoresis results exhibit that the metal complexes cleave pBR322 plasmid DNA in presence of hydrogen peroxide effectively compared to the ligand. The synthesised metallonucleases should lead to a new era for the logical sketch of dominant agents for probing and targeting nucleic acids. This exploration reveals that Cu(II) complex has a valued biological and photochemical profile.     

Transition metal complexes of isonicotinic acid (2-hydroxybenzylidene)hydrazide

A new series of transition metal complexes of Schiff base isonicotinic acid (2-hydroxybenzylidene)hydrazide, HL, have been synthesized. The Schiff base reacted with Cu(II), Ni(II), Co(II), Mn(II), Fe(III) and UO2(II) ions as monobasic tridentate ligand to yield mononuclear complexes of 1:2 (metal:ligand) except that of Cu(II) which form complex of 1:1 (metal:ligand). The ligand and its metal complexes were characterized by elemental analyses, IR, UV-vis, mass and 1H NMR spectra, as well as magnetic moment, conductance measurements, and thermal analyses. All complexes have octahedral configurations except Cu(II) complex which has an extra square planar geometry distorted towards tetrahedral. While, the UO2(II) complex has its favour hepta-coordination. The ligand and its metal complexes were tested against one strain Gram +ve bacteria (Staphylococcus aureus), Gram -ve bacteria (Escherichia coli), and Fungi (Candida albicans). The tested compounds exhibited higher antibacterial activities.     

Catalytic reactivity of new Ni(II), Cu(II) and Sn(II) complexes for decolorization of indigo carmine in aqueous solution,high efficiency of copper complex

A new Ni(II), Cu(II) and Sn(II) Schiff base complexes were synthesized in this work. The characterization of the new complexes is carried out by elemental analysis, FT‐IR, UV–Visible, ¹H NMR and ¹³C NMR spectroscopy, conductance analysis, magnetic measurements and thermal gravimetric analysis. It was found that the ligand behaves as a dibasic bidentate which coordinated to the metal center through two deprotonated hydroxyl groups to form tetrahedral complex with Ni(II) and octahedral complex with Cu(II). The ligand acts as neutral bidentate through azomethine nitrogen and thiazol sulfur to form octahedral complex with Sn(II). The synthesized complexes are evaluated as catalysts for oxidative degradation of indigo carmine dye using H₂O₂ as oxidant and the efficiency of the catalysts is determined. The copper complex shows the best catalytic action with efficiency 92.17% after 25 min.     

Ligational behavior of a bidentate coumarin derivative towards CoII,NiII, and CuII: synthesis,characterization, electrochemistry,and antimicrobial studies

A series of new Co(II), Ni(II), and Cu(II) complexes of Schiff base derived from coumarin have been prepared and characterized by analytical and spectral methods. The Schiff base is synthesized by the condensation of 2,6-diaminopyridine and 3-acetylcoumarin in 1 : 1 stoichiometric ratio. All complexes have 1 : 1 metal : ligand ratio except the nickel complex, where it was found to be 1 : 2. UV-Vis spectra and magnetic moment studies confirm the existence of tetrahedral and octahedral geometries around cobalt(II) and nickel(II) metal ions, respectively, but copper(II) chloride/nitrate/sulfate complexes have square-planar geometry and copper(II) acetate complex is distorted octahedral. ESR spectra of copper complexes at room temperature and liquid nitrogen temperature were tetragonal. All the complexes were found to be more active against bacteria except Ni(II) complex; only CuLSO₄ and CuL(CH₃COO)₂ have shown the enhanced activity against fungi.     

Synthesis and Application of Ruthenium(II) Alkenyl Complexes with Perylene Fluorophores for the Detection of Toxic Vapours and Gases

A series of new ruthenium(II) vinyl complexes has been prepared incorporating perylenemonoimide (PMI) units. This fluorogenic moiety was functionalised with terminal alkyne or pyridyl groups, allowing attachment to the metal either as a vinyl ligand or through the pyridyl nitrogen. The inherent low solubility of the perylene compounds was improved through the design of poly-PEGylated (PEG=polyethylene glycol) units bearing a terminal alkyne or a pyridyl group. By absorbing the compounds on silica, vapours and gases could be detected in the solid state. The reaction of the complexes [Ru(CH=CH-Per^Im)Cl(CO)(py-3PEG)(PPh₃)₂] and [Ru(CH=CH-3PEG)Cl(CO)(py-Per^Im)(PPh₃)₂] with carbon monoxide, isonitrile or cyanide was found to result in modulation of the fluorescence behaviour. The complexes were observed to display solvatochromic effects and the interaction of the complexes with a wide range of other species was also studied. The study suggests that such complexes have potential for the detection of gases or vapours that are toxic to humans.     

Study on Semi-Glycinecresol Red complexes with bivalent metal ions

Semi-Glycinecresol Red (SGCR or H(3)SGCR) was purified by means of chromatography on cellulose and by cation-exchange. A potentiometric, spectrophotometric and ESR study on the complex formation equilibria of several bivalent metal ions with SGCR was performed. The acid-base and metal-ligand stoichiometries were determined, and the formation constants, lambda(max) and absorptivities of the visible-region absorption spectra of the corresponding proton and metal complexes were determined. The copper complexes were examined by ESR spectroscopy. Each metal ion was found to form the 1:1 and 1:2 (metal:ligand) complex species, MSGCR(-) and M(SGCR)(4-)(2), in alkaline solution. However, only Cu(II) was found to form the protonated complexes, CuHSGCR and Cu(HSGCR)(2-)(2), in weakly acidic media. SGCR is suitable as an indicator for Cu(II) in a weakly acidic solution and for Cu(II), Zn(II) and Pb(II) in alkaline solution.     

Octahedral and trigonal prismatic structure preferences in a bicyclic hexaamine cage for zinc(II), cadmium(II) and mercury(II) ions

The synthesis and characterisation of complexes of the hexaamine cage ligand facial-1,5,9,13,20-pentamethyl-3,7,11,15,18,22-hexaazabicyclo[7.7.7]tricosane (fac-(Me)(5)-D(3 h)tricosaneN(6)) with Zn(II), Cd(II) and Hg(II) is reported. Single crystal X-ray structural analyses of the Cd(II) and Hg(II) complexes reveal that the coordination spheres of both cations have an unusual trigonal prismatic stereochemistry organised by the ligand substituents and cavity size. This is unprecedented for hexaamine complexes of these metal ions, and in stark contrast to the distorted octahedral stereochemistry found previously for the analogous Zn(II) complex. An X-ray structural analysis of single crystals of the diprotonated ligand [fac-(Me)(5)-D(3h)tricosaneN(6) - 2H](CF(3)SO(3))(2) shows that it also prefers to adopt a trigonal prismatic structure. The (13)C NMR spectra of the metal complexes indicate that their structures are preserved at 20 degrees C in solution. However, heating the Zn(II) complex to approximately 130 degrees C appears to convert it to the trigonal prismatic form. In contrast cooling the trigonal prismatic Hg(II) complex to -80 degrees C does not convert it to the octahedral structure. The results are also compared to the structures of various other transition metal ion complexes of the same or similar ligands. This comparison yields overall an appreciation of the factors that determine the final structures of complexes formed with such tricosaneN(6) ligands.     

Spectral, thermal and electrical properties of some new azo complexes

Cobalt(ll), nickel(II) and copper(II) acetates react with thymine compound (H2L) to form complexes having the general formula [MH2L(OAC)2(H2O)2]nH2O. However, the interaction of iron(III) chloride with thymine in acetic acid-water medium yields a new complex of the type [FeH2L(OAC)2H2O]OAC.H2O. All the thymine complexes have been characterized by elemental analyses, spectral and magnetic studies where thymine acts as a neutral ligand and the acetate ion behaves as a strong nucleophile during complexation. 6-aryl and thiazolylazo thymine compounds and their metal complexes were synthesized and characterized where the ligands act as a bidentate dibasic. The azo group is not involved in the structure. Thermal decomposition studies of the azo complexes were explained to give more information on the structure of the investigated materials. The effect of some transition metal cations such as Co11, Ni11 and CuII on the electrical behaviour of 6-(2-thiazolylazo)thymine compound is studied. The data obtained obeyed the relation sigma = sigma degrees exp ( - E/2kT) over the temperature range 30-150 degrees C. The observed conductivities of the different complexes follow the order Co < Ni < Cu. It is clear that this trend is depending on the decreasing of the ionic radii and the increasing stability of metal complexes. The calculated mobility of charge carriers is ranged from 10(-5) to 10(-9)cm2/V s suggesting that the conduction of the studied complexes takes place by hopping mechanism.     

Design, synthesis, spectroscopic characterization, biological screening, and DNA nuclease activity of transition metal complexes derived from a tridentate Schiff base

A new series of transition metal complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), Cd(II), Hg(II), and VO(IV) have been designed and synthesized from the Schiff base derived from cinnamidene-4-aminoantipyrine and 2-aminophenol by involving the carbonyl group of 4-aminoantipyrine. The structural features have been arrived from their elemental analyses, magnetic susceptibility, molar conduction, FAB mass, IR, UV-Vis, ¹H NMR and ESR spectral studies. The data show that the complexes have composition of the ML₂ type. The UV-Vis, magnetic susceptibility, and ESR spectral data of the complexes suggest an octahedral geometry around the central metal ion except the VO(IV) complex, which has a square-pyramidal geometry. The redox behavior of the copper and vanadyl complexes has been studied by cyclic voltammetry. The antimicrobial activity of the ligand and its complexes has been extensively studied on microorganisms such as Salmonella typhi, Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus niger, and Rhizoctonia bataicola. It has been found that most of the complexes have higher activities than that of the free ligand. The nuclease activity of the above metal complexes shows that the complexes cleave DNA through redox chemistry. In the presence of H₂O₂, the complexes are capable of cleaving calf thymus DNA. The text was submitted by the authors in English.     

Formation of 1 D and 3 D coordination polymers in the solid state induced by mechanochemical and annealing treatments: bis(3-cyano-pentane-2,4-dionato) metal complexes

Bis(3-cyano-pentane-2,4-dionato) (CNacac) metal complex, [M(CNacac)(2)], which acts as both a metal-ion-like and a ligand-like building unit, forms supramolecular structures by self-assembly. Co-grinding of the metal acetates of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with CNacacH formed a CNacac complex in all cases: mononuclear complex was formed in the cases of Mn(II), Cu(II) and Zn(II), whereas polymeric ones were formed in the cases of Fe(II), Co(II) and Ni(II). Subsequent annealing converted the mononuclear complexes of Mn(II), Cu(II) and Zn(II) to their corresponding polymers as a result of dehydration of the mononuclear complexes. The resultant Mn(II), Fe(II), Co(II), Ni(II) and Zn(II) polymeric complexes had a common 3 D structure with high thermal stability. In the case of Cu(II), a 1 D polymer was obtained. The Mn(II), Cu(II) and Zn(II) polymeric complexes returned to their original mononuclear complexes on exposure to water vapour but they reverted to the polymeric complexes by re-annealing. Co-grinding of metal chlorides with CNacacH and annealing of the mononuclear CNacac complexes prepared from solution reactions were also examined for comparison. [Mn(CNacac)(2)(H(2)O)(2)], [M(CNacac)(2)(H(2)O)] (M=Cu(II) and Zn(II)) and [M(CNacac)(2)](infinity) (M=Mn(II), Fe(II) and Zn(II)) are new compounds, which clearly indicated the power of the combined mechanochemical/annealing method for the synthesis of varied metal coordination complexes.     

Synthesis,characterization, NLO study,and antimicrobial activities of metal complexes derived from 3-(3-(2-hydroxyphenyl)-3-oxoprop-1-enyl)-4H-chromen-4-one and sulfanilamide

A series of metal(II) complexes ML (where M?=?Cu(II), Co(II), Ni(II), Zn(II), Mn(II), Cd(II), and VO(II)) have been prepared from 3-(3-(2-hydroxyphenyl)-3-oxoprop-1-enyl)-4H-chromen-4-one and sulfanilamide. The structures of the complexes have been investigated by elemental analysis, magnetic susceptibility, molar conductance, IR, UV-Vis, NMR, mass, and ESR spectral studies. Conductivity measurements reveal that the complexes are non-electrolytes, except the oxovanadium complex. Spectral and other data show square pyramidal geometry for oxovanadium and octahedral for the other complexes. The redox behaviors of the copper and vanadyl complexes have been studied through cyclic voltammetry. Antimicrobial activities of the compounds against several microorganisms indicate that some complexes have higher activity than free ligand. The compounds may serve as photoactive materials as indicated from their characteristic fluorescence properties. The second harmonic generation efficiency of the ligand was found to be higher than that of urea and KDP.     

Microporous manganese formate: a simple metal-organic porous material with high framework stability and highly selective gas sorption properties

Novel microporous metal-organic framework material composed of Mn(II) and formate ions displays permanent porosity, high thermal stability, and size-selective gas sorption behavior. The framework is stable enough to maintain single crystallinity after the complete guest removal at 150 degrees C under a reduced pressure. Most importantly, it selectively adsorbs H2 and CO2 but not N2 and other gases with larger kinetic diameters, which appears to be due to the small aperture of the channels. Despite a moderate H2 storage capacity, which is however still higher than that of any zeolite, its H2 surface coverage is one of the highest among the known microporous materials. Thus this new zeolite-like material made of a simple organic building block may find useful applications in gas separation and sensor.     

Coordination chemistry of a pi-extended, rigid and redox-active tetrathiafulvalene-fused Schiff-base ligand

A pi-extended, redox-active tetradentate tetrathiafulvalene-fused salphen [salphen = N,N'-phenylenebis(salicylideneimine)] compound (L) was prepared via a direct Schiff-base condensation of the corresponding diamine-tetrathiafulvalene (TTF) precursor with salicylaldehyde. Its chelating coordination ability has been demonstrated by the formation of the corresponding transition metal complexes in the presence of M(OAc)2.nH2O (M = Co(II), Ni(II), Cu(II)) and FeCl3.6H2O. Three complexes have been characterized by single-crystal X-ray diffraction analysis showing that the TTF-salphen ligand coordinates to the metal ions in a planar mode through the nitrogen and oxygen atoms in a N2O2 cis-configuration. In the case of Fe(III), a dinuclear oxo-bridged Fe(III) complex is formed. These paramagnetic complexes are promising building blocks for the construction of dual functional materials due to their unique structural features (planarity and rigidity) as well as their inherent redox properties.     

Synthesis,characterization, DFT modeling and biological studies of new Co(II), Ni(II) and Cu(II) 4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile complexes

Three new metal complexes of 4,6-bis(4-chlorophenyl)-2-amino-1,2-dihydropyridine-3-carbinitrile (L) with Co(II), Ni(II) and Cu(II) were synthesized and characterized with physicochemical and spectroscopic techniques. The data suggest that (L) acts as a bidentate ligand bound to the divalent metal ions through amino N and carbinitrile N atoms having [M(L)₂(H₂O)₂]²⁺ formula (M = metal ions). The theoretical parameters, model structures, charges and molecular orbitals of all possible complexes have been determined using density functional theory. The energy gap of free ligand is ?E = 0.12565 eV, and this value is greater than energy gap of complexes, which indicates that the complexes are more reactive than free ligand. Also, ?E of Co(II) complex is lower than other complexes, which indicates that Co(II) complex is more reactive than Ni(II) and Cu(II) complexes. The antibacterial and antifungal activities of the ligand, metal salts and its complexes were tested against some microorganisms (bacteria and fungi). The complexes showed increased antibacterial and antifungal profile in comparison with the free ligand.     

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.