Some electrochemically generated elemento-organicradical ions and metal complexes as studied by esr

ESR spectra have been obtained for the radical anions Ph_nEl^XXX , where El = P, Si or As, and also for substituted nitrobenzenes. Radical anions were generated by electrochemical reduction within a microwave cavity. The nature and stability of radical ions and other paramagnetic species were established by the investigation of the electrochemical behaviour of the substances. The spin density distribution shows that atoms of the elements in Ph_nEl^XXX are not to be taken as “isolating bridges”. Spin density distributions have also been established for other radical ions.Paramagnetic complexes Mo^V and W^V have been prepared by electrochemical reduction of appropriate molybdenum and tungsten compounds and their structure and magnetic parameters have been established.     

The molecular recognition of tetra(p-t-butyl)tetrathiocalix[4]arene and its derivatives to heavy metal ions

The molecular recognition of tetra(p-t-butyl)tetrathiocalix[4]arene (I)and its three derivatives to heavy metal ions has been investigated by UV spectroscopy and solvent extraction. These derivatives include 5,11,17,23,-tetra-t-butyl-25,26,27,28-tetrakis(acetylmethoxy)tetrathiocalix[4]arene (II), 5,11,17,23-tetra-t-butyl-25,26,27,28-tetrakis(2'-hydroxypropyloxy) tetrathiocalix[4]arene (III), 5,11,17,23,-tetra-t-butyl-25,27-bis(3'-hydroxy propyloxy)tetrathiocalix[4]arene (IV). The UV spectra and solvent extraction of I show that it has an effective molecular recognition to heavy metal ions, especially to Cd(2+), while IV has a special molecular recognition to Ag(+) ion. These results confirmed the feasibilities for I to be applied in separation for toxic heavy metal ions Pb(2+), Cd(2+) and IV to be used as the sensor compound of Ag(+) ion-selective electrode.     

Synthesis of tetra(1,4-dithiacyclohexene)porphyrazine and its metal complexes

The syntheses of tetra, 1, 4-dithiacyclohexene)porphyrazine and its lithium salt, obtained by reaction of 3,6-dithiahexene-1,2-dicarbonitrile with lithium amylate, are described. A series of metal complexes of tetra(1,4-dithiacyclohexene)porphyrazine has been synthesized starting from 3,6-dithiacyclohexene-1,2-dicarbonitrile and the salts of the corresponding metals as well as from the free ligand and metal chlorides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 603–606, May, 1986.     

Dinuclear group VIB metal carbonyl complexes bridged by bis(diphenylphosphino)alkanes

Reactions of the intermediate W(CO)₅THF, generated photochemically from W(CO)₆ in THF, with Ph₂P(CH₂) _n PPh₂ [ = PP; n = 2 (dppe), 4 (dppb), 6 (dpph), 10 (dppd)] at room temperature in THF solutions gave exclusively bimetallic complexes of the (CO)₅WPPW(CO)₅ type. In addition, complexes bridged by diphosphine ligands of the (CO)₄(pip)MPPM(pip)(CO)₄ type (pip = piperidine; M = Mo, W) were prepared by stirring the (CO)₄M(pip)₂ complexes with bis(diphenylphosphino)alkanes in CH₂Cl₂ solution at ambient temperatures. These new bis(diphenylphosphino)alkane-bridged complexes were characterized by i.r., ¹H- and ³¹P-n.m.r. spectroscopies, as well as by elemental analysis.     

Uptake of alkali and alkaline earth metal ions into electrochemically pretreated glassy carbon fibres by flow-through electrolysis

When glassy carbon fibres are used, alkali and alkaline earth metal ions are adsorbed in the micropores which are created or activated by oxidative treatment of the fibres. The average pore radius was estimated to be 2 nm by nitrogen adsorption experiments. Uptake was studied with a flow system consisting of a flow-through carbon-fibre electrode; a dropping mercury electrode at the end of the flow line monitored changes in the metal ion concentrations. The ions were taken up at negative potentials and released at positive potentials. The amount taken up increased in the sequence Na⁺ < Li⁺ < H⁺, suggesting that the ions were desolvated before entering the pore system.     

Optical and electrophysical properties of metal complexes of tetra(1,4-dithiacyclohexeno)porphyrazine

The optical and electrophysical characteristics of metal complexes of tetra-(1,4-dithiacyclohexeno)porphyrazine were measured. The presence of 1,4-dithi-acyclohexene rings in the molecules of the investigated compounds leads to the appearance of bands corresponding to an n * transition in the absorption spectra. The positions of the long-wave bands corresponding to a * transition are determined by the nature of the metal. All of the complexes have semiconductor properties; the specific electrical conductivities range from 10^–11 to 10^{–9 –1}·cm^–1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1276–1279, September, 1986.     

四（2-吡啶基）吡嗪金属配合物的应用研究进展

2,3,5,6-四(2-吡啶基) 吡嗪(tppz)是一类非常具有吸引力的三联吡啶类配体。2,3,5,6-四(2-吡啶基) 吡嗪金属配合物的研究非常重要,在诸多领域如：分子电子、生物化学、磁学、催化和分子传感器等领域具有潜在的应用前景。本文着重对2,3,5,6-四(2-吡啶基) 吡嗪金属配合物近十年应用领域的研究现状进行综述。     

Development of nanomaterial chemosensors for toxic metal ions sensing

Heavy metal ions are harmful to aquatic life and humans owing to their high toxicity and non‐biodegradability, so their removal from wastewater is an important task. Therefore, this work focuses on designing suitable, simple and economical nanosensors to detect and remove these metal ions with high selectivity and sensitivity. Based on this idea, different types of mesoporous materials such as hexagonal SBA‐15, cubic SBA‐16 and spherical MCM‐41, their chloro‐functionalized derivatives, as well as 4‐(4‐nitro‐phenylazo)‐naphthalen‐1‐ol (NPAN) azo dye have been synthesized, with the aim of designing some optical nanosensors for metal ions sensing applications. The mentioned azo dye has been anchored into the chloro‐functionalized mesoporous materials. The designed nanosensors were characterized using scanning and transmission electron microscopy as well as Fourier transform infrared and UV–visible spectral analysis, nitrogen adsorption–desorption isotherms, low‐angle X‐ray diffraction and thermogravimetric analyses. Their optical sensing to various toxic metal ions such as Cd (II), Hg (II), Mn (II), Fe (II), Zn (II) and Pb (II) at different values of pH (1.1, 4.9, 7 and 12) was investigated. The optimization of experimental conditions, including the effect of pH and metal ion concentration, was examined. The experimental results showed that the solution pH had a major impact on metal ion detection. The optical nanosensors respond well to the tested metal ions, as reflected by the enhancement in both absorption and emission spectra upon adding different concentrations of the metal salts and were fully reversible on adding ethylene diamine tetra acetic acid or citric acid to the formed complexes. High values of the binding constants for the designed nanosensors were observed at pHs 7 and 12, confirming the strong chelation of different metals to the nanosensor at these pHs. Also, high binding constants and sensitivity were observed for NPAN‐MCM‐41 as a nanosensor to detect the different metal ions. From the obtained results, we succeeded in transforming the harmful azo dye into an environmentally friendly form via designing of the optical nanosensors used to detect toxic metal ions in wastewater with high sensitivity.     

Radial tetra(ferrocenyl)- and tetra(cymantrenyl)cyclobutadienecobalt complexes: Synthesis and structures

Novel radial tetra(ferrocenyl)- and tetra(cymantrenyl)cyclobutadienecobalt complexes were prepared by metal carbonyls free protocol of [2 + 2] cycloaddition reaction of 1,2-diferrocenyl- or 1,2-dicymantrenylethynes with chlorotris(triphenylphospine)cobalt(I) and carboethoxycyclopentadienide sodium with good yields. The molecular structure of these products was confirmed with X-ray analysis, and their electrochemical behavior was studied.     

Framework coordination polymers of tetra(4-carboxyphenyl)porphyrin and lanthanide ions in crystalline solids

Targeted synthesis of framework coordination polymers was achieved by reacting meso-tetra(4-carboxyphenyl)porphyrin with common salts of lanthanide metal ions. The large size, high coordination numbers and strong affinity for oxo ligands of the latter, combined with favourable hydrothermal reaction conditions in acidic environments, allowed the formation of open three-dimensional single-framework architectures in which the tetra-dentate porphyrin units are inter-coordinated by multinuclear assemblies of the bridging metal ions, which serve as construction pillars, into infinite architectures. Three different modes of coordination polymerisation were characterized by single-crystal X-ray diffraction. They differ by the nuclearity of the metal connectors. All structures exhibit, however, layered organization of the porphyrin-metal domains, and periodically spaced solvent accessible channel voids that penetrate through these layers throughout the corresponding crystals. Thermal analysis provided additional insight into the stability of these polymeric materials.     

An electrochemically prepared sky-blue light emitting ether functionalized polyfluorene as chemosensor for metal ions

Synthesis and electrochemical polymerization of 9,9-bis(2-(2-(2-methoxy ethoxy)ethoxy)ethyl)-fluorene(EO-F)into poly[9,9-bis(2-(2-(2-methoxy ethoxy)ethoxy)ethyl)-fluorene](EO-PF) films are reported. The boron trifluoride diethyl etherate electrolyte enables facile preparation of EO-PF films at lower potential compared to LiClO4/MeCN and the electrochemical polymerizations are discussed. The EO-PF shows good electrochemical behavior and can be dissolved in solvents such as DMSO and THF. The solubility of EO-PF in THF is 2 mg mL 1and the number average molecular weight is35300 with a polydispersity index of 1.65. The side chains on C9position of the monomer maintain unchanged after electrooxidation into corresponding polymer. The EO-PF dissolved in THF under 365 nm ultraviolet light is sky blue light emitting with the Commission Internationale de L Eclairage-CIE coordinates of(0.19, 0.15). The electropolymerized EO-PF is used for the first time in chemosensing metal ions, demonstrating fluorescence quenching for Mn2+and Fe3+while fluorescence enhancement for Cr6+ions.     

Optically switchable chelates: optical control and sensing of metal ions

This study introduces new concepts in the design, synthesis, and in vitro and in vivo characterization, manipulation, and imaging of organic chelates whose association with metal ions is rapidly and reversibly controlled by using light. Di- and tricarboxylic group bearing photochromes, nitrobenzospiropyran (nitroBIPS), undergo rapid and reversible, optically driven transitions between their spiro (SP) and fluorescent merocyanine (MC) states. The MC state of nitroBIPS-8-DA binds tightly to various metal ions resulting in specific shifts in absorption and fluorescence, and the dissociation constant for its Gadolinium complex in water is measured at approximately 5 microM. The metal-bound MC state is converted to the weaker-binding SP state with use of 543 nm light, while the SP to MC transition is complete with use of 365 or 720 nm (2-photon) light within several microseconds. Fluorescence imaging of the MC state of nitroBIPS-8-TriA was used to quantify the rate and efficiency of optical switching and to provide a real-time readout of the state of the optically switchable chelate within living cells.     

Two-dimensional carboxylate bridged network of europium(III)-transition metal(II) glutarate compounds

Four new heterometallic glutarate coordination polymers, [Eu2M(H2O)4][O2C(CH2)3CO2]4.2H2O (M = Mn (1), Fe (2), Co (3) and Ni (4)) have been obtained under hydrothermal synthesis. The single-crystal X-ray diffraction analyses showed that they have two-dimensional frameworks based on the linear polyhedral chains consisting of two nine-coordinated Eu(III)O9 and a six-coordinated M(II)O6. These 1-D MO6-Eu2O16 chains are cross-linked by glutarate ligands as an interchain pillared architecture, whose conformations vary depending upon the transition metals. The magnetic behavior of the compounds show a weak antiferromagnetic interaction, in which shielding of the 4f electrons by the outer shell electrons effectively precludes significant coupling interactions between the Eu-4f electrons and transition metal (M)-3d electrons.     

Radiotracer studies on ion-selective electrode membranes containing metal complexes of a nonylphenoxypoly(ethyleneoxy)ethanol in poly(vinyl chloride) matrices

Radiotracer studies with (133)Ba, (45)Ca and (36)Cl are reported for PVC matrix membranes containing 2-nitrophenyl phenyl ether and the tetraphenylborate of a barium (or calcium) complex with a nonylphenoxypoly(ethyleneoxy)ethanol (NP), Antarox CO880. The results show that there is very limited permeation of radioactive barium and calcium ions through the membrane systems. However, the continued uptake (with time) of radioactive barium ions by the membranes (the uptake of calcium ion is less) suggests that in relation to selective electrode response the stabilization of ions by the NP ligand within the membrane is important in addition to the simple availability of membrane pathways for primary-ion transport through the membrane. Permselectivity to counter-ions is indicated by the non-permeation of radioactive chloride ions.     

Phthalocyanine-centred and naphthalocyanine-centred aryl ether dendrimers with oligo(ethyleneoxy) surface groups

The synthesis of the 1st, 2nd and 3rd generation phthalocyanine-centred and naphthalocyanine-centred poly(aryl ether) dendrimers possessing oligo(ethyleneoxy) surface groups is described. These materials are soluble in polar protic solvents. For both types of macrocycle, the tendency of the non-polar phthalocyanine core towards intermolecular cofacial aggregation is not reduced by peripheral dendritic substitution. However, the prohibition of cofacial aggregation can be achieved by placing the dendritic substituents at the axial sites of the silicon-containing macrocycle. A single crystal X-ray diffraction analysis of one of these compounds beautifully illustrates this concept.     

Aligned nanogold assisted one step sensing and removal of heavy metal ions

We depict a novel strategy exploiting the chemistry of metal ion adsorption for detection and sequestration of toxic heavy metal from processed water using gold nanoparticles capped with 4-aminothiophenol. The interaction between 4-aminothiophenol capped gold nanoparticles and heavy metal ions was studied as a function of time and concentration using TEM, HRTEM, SEM, EDS, and I-V characterization. Experiments confirmed that pH is one of the crucial controlling parameters. Adsorption capacity was monitored using AAS, UV-vis spectroscopy and I-V measurement. In the absence of any alloy formation between Au and heavy metal ions, the desorption of the heavy metal ions from 4-aminothiophenol capped gold nanoparticles surface by pH modulation serves as a mean of collection of heavy metal ions. Experiments revealed that the concentration of heavy metal ions in processed water after adsorption is below the maximum permissible limit set by the WHO.