Tetrasubstituted Peropyrenes Formed by Reductive Aromatization: Synthesis,Functionalization and Characterization

The chromophore class of 1,3,8,10-tetrasubstituted peropyrenes was effectively synthesized from peropyrenequinone via a Zn-mediated reductive aromatization approach. In one step, a symmetric functionalization of the peropyrene backbone introducing silylethers ( 2 , 3 ), pivaloyl ( 4 ), triflyl ( 5 ) and also phosphinite ( 6 ) groups was established. Furthermore, the potential of using 4 and 5 in transition metal catalysed cross couplings was explored leading to 1,3,8,10-tetraaryl ( 8 - 11 ) and tetraalkynyl ( 7 ) peropyrenes. The influence of various substituents on the optoelectronic properties of these π-system extended peropyrenes was investigated in solid state by means of X-ray crystallography, in solution by means of UV-Vis and fluorescence spectroscopy and by their redox properties studied via cyclic voltammetry. By comparison with DFT and TD-DFT calculations, it could be elucidated that introduction of a broad variety of substituents in such versatile one or two step procedures leads to peropyrenes with easily tunable HOMO and LUMO energies ranging in a gap window of 0.8 eV. The frontier molecular orbital energies identify the target molecules as promising candidates for hole transporting semiconductors.     

Voltammetric Label‐free Immunosensors for the Diagnosis of Cystic Echinococcosis

Cystic echinococcosis (CE) or hydatid disease is a parasitic infection caused by Echinococcus granulosus. Early serodiagnosis and continuous monitoring of the disease is very important for medical treatment. Here, we report the detecting of both echinococcus antigen and antibody for the diagnosis of hydatid disease using square wave voltammetry (SWV)‐based immunosensors. The gold electrodes were functionalized using cysteamine/phenylene diisothiocyanate linkers and used for the immunosensors fabrication. The hydatid antigen and antibody immunosensors were constructed by the immobilization of either purified rabbit polyclonal antibody or recombinant antigen B (AgB), respectively on the functionalized gold electrodes surfaces. The detection in both cases was achieved by following the change in the SWV reduction peak current of the ferro/ferricyanide redox couple upon antibody or antigen binding. These immunosensors enabled the detection of echinococcus antigen and antibody within a concentration range of 1 pg.mL^?1 to 1 μg.mL^?1 with detection limits of 0.4 pg.mL^?1 and 0.3 pg.mL^?1, respectively. A preliminary application of the developed immunosensor was performed in spiked serum sample showing good recovery percentages ranging from 102 to 110 % for both hydatid antibody and antigen detection. This easy‐to‐use, sensitive, and low cost quantitative method holds great promise for the early diagnosis of hydatid disease and thus, better managements and treatment outcomes.     

Structure and photophysical and electrochemical properties of a copper porphyrin complex with a three‐dimensional framework

Porphyrins and metalloporphyrins can generally show attractive structural motifs and interesting properties. A new copper porphyrin, namely poly[[μ‐chlorido‐[μ₅‐5,10,15,20‐tetrakis(pyridin‐4‐yl)‐21H,23H‐porphine]tricopper(I)] [aquadichloridocopper(II)]], {[Cu₃(C₄₀H₂₄N₈)Cl][CuCl₂(H₂O)]}_n ( 1 ), was synthesized by the self‐assembly of copper chloride with 5,10,15,20‐tetrakis(pyridin‐4‐yl)‐21H,23H‐porphine under solvothermal conditions. The structure of this copper porphyrin was characterized by single‐crystal X‐ray crystallography and elemental analysis. The porphyrin macrocycle shows a distorted saddle geometry, with the four pyrrole rings slightly distorted in an alternating mode either upwards or downwards. The copper ions show three‐coordinated triangular and four‐coordinated square‐planar geometries. Every copper–porphyrin unit connects to 12 others via four μ₄‐bridging Cu₂Cl moieties to complete the three‐dimensional framework of compound 1 , with isolated CuCl₂(H₂O) units located in the voids. This copper porphyrin displays a red photoluminescence. Electrochemical measurements showed that compound 1 has two redox waves (E_1/2 = ?160 and 91 mV).     

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.     

Synthesis and Electronic Properties of Novel 5,7-Diazapentacene Derivatives

A route to the synthesis of novel 5,7-diazapentacenes and some preliminary studies on their properties is reported. A single crystal X-ray diffraction study of the dihexyl derivative showed it had formed a dimer during the analysis. The materials possess lower lying frontier orbitals than pentacene and may have potential applications in organic electronic devices. This synthetic method may be applicable to the synthesis of other azaacenes.     

Electrochemical methods for analysing and controlling charge transfer at the electrode–tissue interface

There have been rapid advances in the development of new materials for use in electrode–tissue interfacing. The development of conducting polymers, conducting hydrogels, carbon nanotubes, graphene and other conducting materials has provided a rich landscape for controlling charge transfer at the electrode–tissue interface and hence to monitor and manipulate cell behaviour. These materials have been used in tissue-engineered constructs to direct and control cell proliferation, growth and differentiation. However, their translation to clinical devices has been less successful. In this review, the use of electroanalytical techniques to develop an understanding of charge transfer at the electrode–tissue interface is discussed. In particular, the impact of solution and electrode conditions on charge injection capacity is demonstrated. The importance of standardised testing methods and the correlation of electrochemical and electrophysiological performance show the limitations of empirical studies and help define key electrode properties for clinical devices. The development of a sound theoretical basis for charge transfer at this increasingly important interface is being advocated to improve clinical outcomes and device lifetime and reduce power usage.     

Synthesis and electrochemical properties of copper(II), manganese(III) phthalocyanines bearing chalcone groups at peripheral or nonperipheral positions

In this study, new chalcone compound 1 , new phthalonitrile derivatives 2 and 3, new copper(II), manganese(III) phthalocyanines bearing chalcone groups at peripheral or nonperipheral positions were synthesized. Electrochemistry of tetra-(4-{(2 E )-3-[2-fluoro-4-(trifluoromethyl)phenyl]prop-2-enoyl}phenoxy) substituted Co(II)Pc and Mn(III)Pcs were studied with cyclic voltammetry (CV) to determine the redox properties of the phthalocyanines. According to the results, while the CuPcs 2a and 3a showed two Pc based reduction reactions and one Pc based oxidation reaction, MnPcs 2b and 3b gave two metal-based reduction reactions. All the redox processes are shifted toward positive potentials as a result of the increased electron-withdrawing ability of the trifluoromethyl substituents.     

Antioxidant behaviour of 2′‐hydroxy‐chalcones: a study of their electrochemical properties

The electrochemical behaviour of 13 chalcone analogues was systematically studied by means of cyclic voltammetry and chronoamperometry at a glassy carbon (GC), gold and platinum working electrodes using two different supporting electrolyte/solvent combinations. It was found that chalcone analogues can be easily oxidized at both GC and gold working electrodes, but not at a platinum electrode. Principal component analysis was further employed to reveal similarities/dissimilarities between oxidation potentials, chronoamperometric signals and ability of the compounds to scavenge the reactive oxygen species H₂O₂. The study reveals the inverse proportional relationship between the scavenging ability of H₂O₂, expressed as IC₅₀, and chronoamperometric signal at 800 mV using gold as working electrode. Copyright © 2012 John Wiley & Sons, Ltd.     

Cyclic voltammetry study of electrodeposition of CuGaSe2 thin films on ITO-glass substrates

The electrodeposition mechanism of CuGaSe₂ (CGS) thin films on ITO substrates has been investigated using cyclic voltammetry technique. The cyclic voltammetric study was performed in unitary Cu, Ga and Se systems, binary Cu–Se, Ga–Se systems and ternary Cu–Ga–Se system. The electrodeposition metallic Ga from Ga unitary electrolytes is impossible due to its low reduction potential. No reduction peak was found for the reduction of Ga³⁺ to Ga in the cyclic voltammogram of unitary system. However, in the cyclic voltammogram of ternary Cu–Ga–Se system, reduction peak at −0.6 V was observed with addition of GaCl₃. Also, current density of the peak was increased with increasing concentration of GaCl₃. It is corresponded to the formation of gallium selenides and/or copper–gallium–selenium compounds. The contents of Ga in the films were significantly changed from −0.4 V to −0.6 V. SEM and XRD analysis also showed that surface morphology and crystalline phase of films were significantly changed with increasing Ga content.     

Electroreduction of cationic fluorene complexes of manganese

Using cyclic voltammetry method, the reduction of cationic η⁶-fluorene complexes of manganese [(η⁶-9-R-C₁₃H₉)Mn(CO)₂L]PF₆ (L = CO, R = H (1 ⁺); L = CO, R = CH₃ (2 ⁺); L = PⁿBu₃, R = H (3 ⁺); L = CO, R = ^tBu (4 ⁺)) is studied. It is shown that, depending on the nature of a substituent in the position 9 of the fluorene ligand, the reduction occurs either with the detachment of an H atom from position 9 to give zwitterion compounds (complexes 1 ^±, 2 ^±, 3 ^±) or with the attachment of an H atom into the coordinated ring of the fluorene ligand to given η⁵-cyclohexadienyl complex (η⁵-9-^tBu-C₁₃H₉)Mn(CO)₃ (5).