A novel copper(ıı) phthalocyanine-modified multiwalled carbon nanotube-based electrode for sensitive electrochemical detection of bisphenol A

A novel copper(ii) phthalocyanine (CuPc)-modified multiwalled carbon nanotube-based electrode was prepared for the sensitive electrochemical detection of bisphenol A, by the modification of a pencil graphite electrode via the adsorption method.

Electrochemical behavior of electrodes modified with metalloporphyrin and multiwalled carbon nanotubes for the reduction of oxygen, proton and carbon dioxide

Iron porphyrin and cobalt porphyrin were respectively modified on glassy carbon (GC) electrodes together with multiwalled carbon nanotubes (MWCNTs), and the modified electrodes were characterized by X-ray photoelectron spectroscopy (XPS). Their electrochemical performance for the reduction of oxygen (O2) , proton (H+) and carbon dioxide (CO2) were respectively investigated and compared by cyclic voltammetry (CV). The results showed that iron porphyrin-MWCNT modified electrode always had a better performance than cobalt porphyrin-MWCNT modified electrode. It is proposed that iron porphyrin-MWCNT modified electrode will have promising application in electrochemical architectures like microbial fuel cells (MFCs) and microbial electrolysis cells (MECs) for its good biocompatibility, easy availability, as well as excellent electrochemical performance.

Nanostructured thin films based on phthalocyanines: electrochromic displays and sensors

The group of the University of Valladolid is a multidisciplinary team formed by chemists, physicists and engineers. The activities of the group are focused to the study of the physicochemical properties of nanostructured Langmuir-Blodgett thin films based on phthalocyanines and their applications. Films of a variety of phthalocyanine molecules including several metallophthalocyanines, lanthanide double decker phthalocyanines and heteroleptic derivatives have been prepared. Their spectroelectrochemical properties have been described in detail and compared with those observed in disordered casted films or microcrystalline evaporated films. The group has dedicated special attention to films based on rare earth double decker compounds due to their unique semiconducting, optical and electrochemical properties. A rich electrochromism has been demonstrated in thin films of this family of compounds. The reversibility is improved in nanostructured Langmuir-Blodgett films. This has permitted development of an electrochromic display that can change its color from blue to green and finally to red. At the present moment, our main objective is the design of sensors able to detect gases and liquids. It has been demonstrated that thin film assemblies based on rare earth bisphthalocyanines modify their conductivity and their optical properties in the presence of electron donor or electron acceptors gases. Changes are also observed when the devices are exposed to Volatile Organic Compounds such as esters, alcohols or aldehydes which are responsible of odors in foods and beverages. Liquid sensors have also been developed. Their working principle is based in the fact that the rich electrochemical properties of phthalocyanine thin films are extremely sensitive to the nature of the electrolytic solution. Arrays of phthalocyanines have been used to construct an electronic nose able to discriminate odors from a variety of foods and beverages. Similarly, phthalocyanines have also been used to construct an electronic tongue based on voltammetric sensors. This is one of the main contributions of the group to the field of sensors.

A spectrophotometric and thermodynamic study of the sitting-atop complex formation from reaction between free base meso-tetraarylporphyrins and zirconyl nitrate in chloroform solution

The sitting-atop complexation of meso-tetraarylporphyrins and its para-substituted derivatives (H(2)t(4-X)pp, X:H, Br, Cl, CH(CH(3))(2), OCH(3), CH(3)), as electron donors, with zirconyl, as an electron acceptor, have been investigated spectrophotometrically in chloroform. The mole ratio studies based on physicochemical techniques were employed clearly and revealed the formation of 1:1 sitting-atop complexes which was confirmed by UV-vis, (1)H NMR and IR spectroscopic data. The value of the formation constant was estimated for each complex using a nonlinear optimization of the complex absorbance vs. mole ratio data by package KINFIT. The results showed that the stability of these complexes decreases with the temperature enhancement. Thermodynamic parameters, DeltaG degrees , DeltaH degrees and DeltaS degrees , of the SAT complexes have been determined from the temperature dependence of formation constants by Van't Hoff equation. Also, the influence of the substituents of the aryl rings in H(2)t(4-X)pp on the stability of the SAT complexes is discussed.

Partially and fully β-brominated Mn-porphyrins in P450 biomimetic systems: Effects of the degree of bromination on electrochemical and catalytic properties

Beta-hexabromo-5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrinatomanganese(III) chloride (Mn(III)(Br6TCMPP)Cl) was prepared by selective Br2-hexabromation of its parent non-brominated manganese complex (Mn(III)(TCMPP)Cl), whereas the octabrominated analogue beta-octabromo-5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrinatomanganese(III) chloride (Mn(III)(Br8TCMPP)Cl) was synthesized via metallation of the corresponding free-base. Beta-octabromo-5,10,15,20-tetrakis(4-carbomethoxyphenyl)porphyrin was obtained by demetallation of its brominated Cu(II) derivative, which, in its turn, was prepared by either a Br2 or an N-bromosuccinimide protocol. Relative to Mn(III)(TCMPP)Cl (E(1/2) = -0.16 V vs. normal hydrogen electrode, CH2Cl2), the Mn(III)/Mn(II) reduction potential of Mn(III)(Br8TCMPP)Cl and Mn(III)(Br6TCMPP)Cl showed anodic shifts of 0.43 and 0.33 V, respectively, which corresponded to a linear shift of 0.05 V per bromine added. These manganese complexes were evaluated as cytochrome P450 mimics in catalytic iodosylbenzene (PhIO)-oxidations of cyclohexane and cyclohexene. In aerobic PhIO-oxidation of cyclohexene, epoxidation and allylic autoxidation reactions were inversely related, competitive processes; the most efficient P450-mimics were the least effective autoxidation catalysts. Mn(III)(Br6TCMPP)Cl was more efficient as epoxidation or hydroxylation catalyst than both its fully and non-beta-brominated counterparts were. There was no linear relationship between the catalytic efficiency and both the number of bromine substituents and the Mn(III)/Mn(II) potential; these observations were compared to Lyons system literature data and discussed. Analogously to enzymatic optimum pH effects, an optimum redox potential effect is suggested as relevant in designing and understanding cytochrome P450 biomimetic catalysts.