Electrochemistry of Cobalta Bis(dicarbollide) Ions Substituted at Carbon Atoms with Hydrophilic Alkylhydroxy and Carboxy Groups

In this study we explore the effect on the electrochemical signals in aqueous buffers of the presence of hydrophilic alkylhydroxy and carboxy groups on the carbon atoms of cobalta bis(dicarbollide) ions. The oxygen-containing exo-skeletal substituents of cobalta bis(dicarbollide) ions belong to the perspective building blocks that are considered for bioconjugation. Carbon substitution provides wider versatility and applicability in terms of the flexibility of possible chemical pathways. However, until recently, the electrochemistry of compounds substituted only on boron atoms could be studied, due to the unavailability of carbon-substituted congeners. In the present study, electrochemistry in aqueous phosphate buffers is considered along with the dependence of electrochemical response on pH and concentration. The compounds used show electrochemical signals around −1.3 and +1.1 V of similar or slightly higher intensities than in the parent cobalta bis(dicarbollide) ion. The signals at positive electrochemical potential correspond to irreversible oxidation of the boron cage (the C2B9 building block) and at negative potential correspond to the reversible redox process of (CoIII/CoII) at the central atom. Although the first signal is typically sharp and its potential can be altered by a number of substituents, the second signal is complex and is composed of three overlapping peaks. This signal shows sigmoidal character at higher concentrations and may be used as a diagnostic tool for aggregation in solution. Surprisingly enough, the observed effects of the site of substitution (boron or carbon) and between individual groups on the electrochemical response were insignificant. Therefore, the substitutions would preserve promising properties of the parent cage for redox labelling, but would not allow for the further tuning of signal position in the electrochemical window.     

Anthracene Substituted Co (II) and Cu (II) phthalocyanines; Preparations,Investigation of Catalytical and Electrochemical Behaviors

An approach to investigation of catalytical behaviors of Co (II) and Cu (II) phthalocyanines is reported that is based on changing any parameter to effect these behaviors. Towards this end, new anthracene substituted Co (II) and Cu (II) phthalocyanines were prepared and characterized spectroscopic methods. New cobalt (II) and copper (II) phthalocyanines were used as catalyst for oxidation of different phenolic compounds (such as 2,3‐dichlorophenol, 4‐methoxyphenol, 4‐nitrophenol, 2,3,6‐trimethylphenol) with different oxidants. Then, electrochemical characterization of cobalt (II) and copper (II) phthallocyanines were determined by using cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. Although copper (II) phthalocyanine showed similar Pc based electron transfer processes, cobalt (II) phthalocyanine showed metal and ligand based reduction reactions as expected.     

Preparation,characterization of new Co(II) and Cu(II) phthalocyanines and their catalytic performances in aerobic oxidation of substituted phenols

The host–guest inclusion complex of meta-cresol (m-cresol, liquid at room temperature, guest molecule) is synthesized with β-cyclodextrin (β-CD, host molecule). The inclusion complex is characterized by various techniques like nuclear magnetic resonance, powder X-ray diffraction, field emission scanning electron microscopy and spectroscopic (steady state as well as time-resolved) techniques. To the best of our knowledge, no literature data is available on the photophysical properties (especially fluorescence upon photoexcitation) of m-cresol in liquid media till date. Our spectroscopic studies exhibit some interesting photophysical properties of m-cresol and its inclusion complex with β-CD in different liquid media. The present work is important in view of the various potential applications of m-cresol in science, technology and medicine.     

Synthesis,characterization and catalytic activity of peripherally tetra‐substituted Co(II) phthalocyanines for cyclohexene oxidation

New 3,3‐diphenylpropoxyphthalonitrile (5) was obtained from 3,3‐diphenylpropanol (3) and 4‐nitrophthalonitrile (4) with K₂CO₃ in DMF at 50 °C. The novel cobalt(II) phthalocyanine complexes, tetrakis‐[2‐(1,4‐dioxa‐8‐azaspiro[4.5]dec‐8‐yl)ethoxy] phthalocyaninato cobalt(II) (2) and tetrakis‐(3,3‐diphenylpropoxy)phthalocyaninato cobalt(II) (6) were prepared by the reaction of the phthalonitrile derivatives 1 and 5 with CoCl₂ by microwave irradiation in 2‐(dimethylamino)ethanol for at 175 °C, 350 W for 7 and 10 min, respectively. These new cobalt(II)phthalocyanine complexes were characterized by spectroscopic methods (IR, UV–visible and mass spectroscopy) as well as elemental analysis. Complexes 2 and 6 are employed as catalyst for the oxidation of cyclohexene using tert‐butyl hydroperoxide (TBHP), m‐chloroperoxybenzoic acid (m‐CPBA), aerobic oxygen and hydrogen peroxide (H₂O₂) as oxidant. It is observed that both complexes can selectively oxidize cyclohexene to give 2‐cyclohexene‐1‐ol as major product, and 2‐cyclohexen‐1‐one and cyclohexene oxide as minor products. TBHP was found to be the best oxidant since minimal destruction of the catalyst, higher selectivity and conversion were observed in the products. Copyright © 2012 John Wiley & Sons, Ltd.     

Cobalt-modified nickel–zinc catalyst for electrooxidation of methanol in alkaline medium

Cobalt-modified nickel-zinc catalyst CuNi(Zn)Co is prepared on a copper substrate by using electrodeposition. Its catalytic efficiency for methanol oxidation is studied with cyclic voltammetry, chronoamperometry, and chronopotentiometry techniques. The surface morphology and chemical composition of catalyst are characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The oxidation kinetic parameters activation energy (Ea), active species on the surface (Γ), and rate constant (k) are determined from cyclic voltammograms which are performed at different methanol concentrations and temperatures. The results show that Ni(Zn)Co catalyst has higher catalytic activity than Ni, Co, and NiZn coatings as a composite catalyst for a promising choice of methanol electrooxidation in the alkaline medium.     

Voltammetric and Impedimetric Detection of Interaction Between Dacarbazine and Nucleic Acids

Dacarbazine (DTIC) is a chemotherapy drug that is used for the treatment of Hodgkin's lymphoma, malignant melanoma, childhood solid tumors and soft tissue sarcoma. The surface confined interaction between DTIC and nucleic acids was investigated for the first time in this study by using both differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) in combination with disposable pencil graphite electrodes. The oxidation signals of DTIC and guanine were measured before and after interaction process using DPV technique. The interaction of DTIC with nucleic acids; poly[A], poly[G], or double stranded of poly[A]‐poly[T] and poly[G]‐poly[C] was also examined using DPV. Furthermore, EIS technique was utilized for detection of the interaction between DTIC and nucleic acids; ssDNA/dsDNA, poly[A], poly[G], or double stranded poly[A]‐poly[T] and poly[G]‐poly[C].     

Accelerated screening of phage-display output with alkaline phosphatase fusions

When using multiple targets and libraries, selection of affinity reagents from phage-displayed libraries is a relatively time-consuming process. Herein, we describe an automation-amenable approach to accelerate the process by using alkaline phosphatase (AP) fusion proteins in place of the phage ELISA screening and subsequent confirmation steps with purified protein. After two or three rounds of affinity selection, the open reading frames that encode the affinity selected molecules (i.e., antibody fragments, engineered scaffold proteins, combinatorial peptides) are amplified from the phage or phagemid DNA molecules by PCR and cloned en masse by a Ligation Independent Cloning (LIC) method into a plasmid encoding a highly active variant of E. coli AP. This time-saving process identifies affinity reagents that work out of context of the phage and that can be used in various downstream enzyme linked binding assays. The utility of this approach was demonstrated by analyzing single-chain antibodies (scFvs), engineered fibronectin type III domains (FN3), and combinatorial peptides that were selected for binding to the Epsin N-terminal Homology (ENTH) domain of epsin 1, the c-Src SH3 domain, and the appendage domain of the gamma subunit of the clathrin adaptor complex, AP-1, respectively.     

New type of tetrazine‐substituted metallophthalocyanines by microwave irradiation: Synthesis and characterization

5,6‐bis(4‐methylphenyl)‐2,3‐dihydro‐1,2,3,4‐tetrazine 2 was synthesized by the dimerization of ethyl p‐methylbenzoateformylhydrazone 1 in hydrazinehydrate solution. 2,3‐bis(4‐methylphenyl)‐6,7,14,15‐tetrahydro[1,2,3,4]tetrazino [2,3d][1,8, 4,5]benzodithia‐diazecine‐10,11‐dicarbonitrile 4 was sythesized by cyclization reaction of tetrazine monomer 2 onto 1,2‐bis‐(2‐iodoethylmercapto)‐4,5‐dicyanobenzene 3 . Co(II) and Cu(II) phthalocyanine complexes were prepared by reaction of the dinitrile compound ( 4 ) with the chlorides of Co(II), Cu(II), and DMAE at 175°C, 350 W in a microwave oven for 10 min. Zn(II)‐phthalocyanine complex was prepared by reaction of the dinitrile compound 4 with the acetate of Zn(II) and DMAE at 175°C, 350 W in a microwave oven for 10 min. The new compounds were characterized by a combination of IR, ¹H‐NMR, ¹³C NMR, UV‐vis, elemental analysis, and MS spectral data. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:456–461, 2010; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20623     

Probing mixed valence in a new tppz-bridged diruthenium(III,II) complex {(mu-tppz)[Ru(bik)Cl]2}3+ (tppz=2,3,5,6-tetrakis(2-pyridyl)pyrazine, bik=2,2'-bis(1-methylimidazolyl)ketone): EPR silence, intervalence absorption, and nu(CO) line broadening

The complex dication of the diruthenium(II) compound {(mu-tppz)[Ru(bik)Cl]2}(ClO4)2 can be oxidized and reduced in two one-electron steps each. In CH3CN/0.1 M Bu4NPF6, the odd-electron intermediates{(mu-tppz)[Ru(bik)Cl]2}n+, n=1 and 3, have comproportionation constants of 7x10(8) and 1x10(5), respectively. Both exhibit near-infrared absorptions, in the case of n=3 the 1640 nm band (epsilon=1200 M-1 cm-1, Deltanu1/2=1560 cm-1) is attributed to an intervalence charge-transfer transition. While the mixed-valent intermediate (n=3) is EPR silent even at 4 K, the n=1 form shows g(parallel) 2.005 and g( perpendicular) 1.994 at that temperature, signifying a diruthenium(II) complex of the tppz*- radical anion. The variation of energy and intensity of nuCO and of the ring vibration band around 1590 cm-1 has been monitored not only for {(mu-tppz)[Ru(bik)Cl]2}n+, n=0-4, but also for the mononuclear {(tppz)Ru(bik)Cl}n+, n=0-2. In the dinuclear complex the carbonyl stretching bands of the spectator ligand bik are shifted by about 15 cm-1 on each one-electron-transfer step, increasing with the positive charge. The mixed-valent {(mu-tppz)[Ru(bik)Cl]2}3+ shows a perceptibly broader nuCO band, suggesting incomplete valence averaging (partial localization).