bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparative Electrochemical Properties of Phthalocyanines Bearing Fc(CH2)n- and/or Alkyl Substituents in Non-Peripheral and/or Peripheral Positions.
Authors: Swarts Jannie C 
Published: February 2020

Phthalocyanines and their metal complexes1have been studied for their interesting chemical, electrochemical, thermal and photochemical properties as well as for the numerous applications they may be used for. These include the vast domain of catalysis, as photosensitizers for photodynamic therapy of cancer, ink-jet printing components and in memory devices. The phthalocyanine macrocycle may be modified by introduction of redox-active moieties (here ferrocene) in peripheral or non-peripheral positions to append the existing macrocycle redox centers (usually four are observable in DCM as solvent). Non-peripherally substituted long alkyl chains also influence the redox and other physical properties such as mesophase behaviour.
It is well known that the redox properties of phthalocyanine macrocycles change depending on the type of metal that is coordinated in the macrocyclic cavity. The tendency of cadmium macrocycles to oligomerise even to heptamers is less known. Further changes in the redox properties of this macrocycle may be induced by systematically changing the “meso” or “outer” nitrogen atoms to CH ultimately to liberate a benzoporphyrin.
In this presentation, the synthesis of the above compounds will be presented very shortly. Thereafter, the influence that alkyl chain length (expressed as R = C10H21 – C18H37 above),2 linker atom X = S or O, metallocenyl chain length ( n = 1 – 4), coordinated metal species, M, and the effect of axial dimerisartion and trimerisation of Cd complexes on especially the redox properties of these unique macrocycles will be highlighted and brief mention will be made of the mesophase behaviour these changes induce. Electrochemical results obtained for the systematical conversion from phthalocyanine to benzoporphyrin will also be presented.
References
1. E. Fourie, J. C. Swarts, I. Chambrier, M. J. Cook, Dalton Trans., 1145-1154 (2009).
2. J. C. Swarts, E. H. G. Langner, N. Krokeide-Hove, M. J. Cook, J. Mater. Chem., 11, 434-443 (2001).

Figure 1
Intermolecular Communication in a Supramolecular Assembly of Porphyrins and Phthalocyanines
Authors: Tanaka Kentaro 
Published: February 2020

Programmable construction of a multiple molecular system is the best measure for bringing out the integrated properties evolved from the intermolecular communications in the molecular assemblies. Especially, controlling sequential and spatial arrangements of building components in the molecular array is crucial for developing novel functions of the designer nanoarchitecture. Since organized assemblies of porphyrins and phthalocyanines are promising for generating higher functionalized systems, we have recently reported the supramolecular arrays in which a porphyrin and a phthalocyanine are connected by four-fold rotaxanes [1-4] and sequential and spatial organization of metalloporphyrins inside a peptide duplex [5].
In this paper, we will present construction of the suplamolecular arrays of a metallo-porphyrin and a metallo-phthalocyanine through four-fold rotaxane formation between a tetradactyl porphyrin with alkylammmonium moieties and a phthalocyanine bearing four crown ethers (Figure 1a) and significant electronic communications between the metal complexes (Figure 1b). Since synthetic strategy for the rotaxane is applicable to pre- and post-metallation of both porphyrin and phthalocyanine centers, the four-fold rotaxane framework is suitable for homo- and hetero-assemblage of metal ions. In a homo-dinuclear Cu2+ complex of the four-fold rotaxane, the Cu2+-porphyrin and the Cu2+-phthalocyanine showed a switching behavior in the spin–spin interaction through change of the spatial distance between the two metal centers induced by protonation and deprotonation.
1) Y. Yamada, M. Okamoto, K. Furukawa, T. Kato, and K. Tanaka, Angew. Chem. Int. Ed.,
51, 709–713 (2012). 2) Y. Yamada, N. Mihara, and K. Tanaka, Dalton Trans., 42, 15873-15876 (2013). 3) Y. Yamada, N. Mihara, S. Shibano, K. Sugimoto, and K. Tanaka, J. Am. Chem. Soc., 135, 11505-11508 (2013). 4) Y. Yamada, M. Okada, and K. Tanaka, Chem. Commun., 49, 11053-11055 (2013). 5) Y. Yamada, T. Kubota, M. Nishio, and K. Tanaka, J. Am. Chem. Soc., 136, 6505-6509 (2014).

Figure 1
Substrate-Dependent Oxidation with Alkyl Hydroperoxide Mediated By Iron Porphyrin Coordinated By Thiolate
Authors: Higuchi Tsunehiko 
Published: February 2020

Alkane and arene hydroxylation by cytochrome P450 is one of the most powerful chemical processes in biological systems. The highly reactive intermediate in cytochrome P450 catalysis has aroused broad interests and has been the subject for extensive investigations. SR complex successfully created by us is the first synthetic heme thiolate complex that retains its thiolate coordination structure during catalytic oxidation reaction. We have focused on the alkyl hydroperoxide-heme thiolate chemistry. We previously found that SR complex efficiently catalyzed one-electron oxidation of 2,4,6-tri-tert-butylphenol (TBPH) with cumene hydroperoxide (CHPO) or tert-butyl hydroperoxide to afford 2,4,6-tri-tert-butylphenoxyl radical (TBP•). Recently, 2-methyl-1-phenylpropan-2-yl hydroperoxide (MPPH) has been used as a mechanistic probe for O-O bond cleavage mode on catalysis of metal complex. MPPH is known to give benzyl radical-derived products and acetone via unstable alkoxyl radical in the case of homolytic O-O bond cleavage whereas it simply affords 2-methyl-1-phenyl-2-propanol (MPPOH) in the case of heterolysis. Here we report the substrate oxidation mechanism with CHPO and MPPH catalyzed by SR complex.
We found that SR complex lost its thiolate coordination after the addition of MPPH (1 equiv. to SR complex) even in the presence of large excess amount of phenol with an electron-withdrawing substituent. On the other hand, the use of TBPH or 2,6-di-tert-butylphenol as a substrate lead to retention of the thiolate coordination.
Next, equilibrium constant K’ values of THF coordination to SRs were determined by Benesi-Hildebrand plot (inverse of absorption spectral change versus inverse of THF concentration). We plot K’ versus reaction rate since correlation between the two factor was expected. The plot clearly showed that the reaction rate was almost proportionate to K’ value from high linearity of the plot in terms of SR complexes. This result suggests that hydroperoxide coordination step is rate-determining step. Putting together these results, alkyl hydroperoxide-heme-thiolate complex is suggested to be an actual active intermediate.
Multi-Step Energy and Electron Transfer in a 'v-Configured' Supramolecular Bodipy-Azabodipy-Fullerene Triad
Authors: D'Souza Francis , Bandi Venugopal , D'Souza Fiona P. , Gobeze Haptom B. 
Published: February 2020

Supramolecular multi-modular donor-acceptor systems are useful for solar-fuel and solar-electricity generation, and also for building optoelectronic devices. In the present contribution, a novel photosynthetic antenna-reaction center model compound composed of covalently linked BF2-chelated dipyrromethene (BODIPY), BF2-chelated azadipyrromethene (azaBODIPY) and fullerene (C60), in a ‘V-Configuration’, has been newly synthesized and characterized using a multi-step synthetic procedure.1 Optical absorbance and steady-state fluorescence, computational, and electrochemical studies were systematically performed in nonpolar, toluene and polar, benzonitrile solvents to establish the molecular integrity of the triad and establish an energy level diagram revealing different photochemical events. The geometry obtained by B3LYP/6-31G* calculations revealed the anticipated V-configuration of the BODIPY-azaBODIPY-C60 triad. The location of the frontier orbitals in the triad tracked the site of electron transfer determined from electrochemical studies. The different photochemical events originated from 1BODIPY* were realized from the energy level diagram. Accordingly, 1BODIPY* resulted in competitive ultrafast energy transfer to produce BODIPY-1azaBODIPY*-C60 and electron transfer to produce BODIPY·+-azaBODIPY-C60
·- as major photochemical events. The charge separated state persisted for few nanoseconds prior populating 3C60
* which in turn revealed an unusual triplet-triplet energy transfer to produce 3azaBODIPY* prior returning to the ground state. These findings delineate the importance of multi-modular systems in energy harvesting, and more importantly, their utility in building multi-function performing optoelectronic devices.

V. Bandi, F. P. D’Souza, H. Gobeze, F. D’Souza, Chem. Eur. J. 2015, in press.
Polar Self-Assembled Subphthalocyanine Columnar Stacks
Authors: González-Rodríguez David , Torres Tomas , Guilleme Julia 
Published: February 2020

Subphthalocyanines (SubPcs) are singular cone-shaped molecules with unique physicochemical properties that render them promising light-harvesting and/or donor units for photovoltaic and light-emitting applications. We were very interested in studying if such molecules could be organized in columnar stacks, both in solution and liquid-crystalline phases by hydrogen-bonding and p-p stacking interactions. The columnar aggregation of these non-planar molecules with axial dipole moments represents in itself a challenging task. Our motivation comes from the possibility of obtaining supramolecular chiral nanofibers and condensed phases that can be aligned in the presence of electric fields, yielding nanomaterials with permanent polarization and unusual ferroelectric and piezoelectric properties.

Figure 1
Advances in Voltammetric Sensors Using Combinations of Phthalocyanines with Nanoparticles and/or Biomolecules in LB and LbL Films
Authors: Rodriguez-Mendez Maria Luz , Medina-Plaza Cristina , Garcia-Hernandez Celia , Garcia-Cabezon Cristina , Martin-Pedrosa Fernando , Muñoz Raquel , de Saja Jose Antonio 
Published: February 2020

Electrochemical sensors have been prepared using a range of materials and using a variety of methods. The selection of phthalocyanines or nanoparticles as sensing materials in electrochemical sensors was inspired in their electrocatalytic properties1. In turn, nanostructured sensors prepared using the Langmuir-Blodgett (LB) or the electrostatic Layer-by-Layer (LbL) techniques have the advantage of the enhanced number of active sites that has a reflect in the increase in the intensity. The control of molecular architectures afforded by these techniques can led to the development of a variety of devices where synergy is achieved by combining distinct materials, including organic-inorganic hybrids2.
In this work combinations of phthalocyanines with nanoparticles and/or biomolecules in LB and LbL films have been developed and their structures have been analyzed. The films have been used as voltammetric sensors for the detection of compounds of interest in the food industry (i.e. phenols or organic acids). The role of the molecular interactions in the electrocatalytic properties or as biomimetic systems to immobilize biomolecules has been studied and the existence of synergistic effects has been evidenced. For instance, the combination of phthalocyanines with gold nanoparticles in LB films produced an increase in the sensitivity towards phenols and detection limits of 10-7 mol.L-1 were attained. Similar detection limits could be obtained by combining phthalocyanines with silver nanoparticles in LbL films. LB and LbL films combining phthalocyanines and amphiphilic molecules provided biomimetic environments where enzymes could preserve their functionality. Detection limits as low as 10-8 mol.L-1 towards phenols were attained.
References:

1M.L. Rodríguez-Méndez, C. Medina, J.A. de Saja, C. Apetrei, R. Muñoz sensor arrays based on phthalocyanines: new developments on nanostructured and biomimetic electrochemical sensors. In Multisensor systems for chemical analysis: materials and sensors. Eds. L. Lvova, D. Kirsanov, C. Di Natale, and A. Legin. PAN STANFORD PUBLISHING. Chapter 4, 70-109 (2012)

2F. J. Pavinatto, E. G. R. Fernandez, P. Alessio J..C. Constantino, J. A. de Saja, V. Zucolotto,d O. N. Oliveira Jr. C. Apetrei, M. L. Rodriguez-MendezOptimized architecture for Tyrosinase-containing Langmuir-Blodgett films to detect pyrogallol J. Materials Chemistry 21, 4995-5003 2011
Figure 1: LB film formed by phthalocyanins/amphiphiles and nanoparticles

Figure 1
Power Spectral Density Analysis of the Corrosion Potential Fluctuation of Stainless Steel 316L in Early Stages of Exposure to Caribbean Sea Water
Authors: Espinosa Carlos , Veleva Lucien Petrova , Lopez Juan Luis 
Published: February 2020

Stainless Steel 316 L samples were exposed for one month to Caribbean sea water. The fluctuations of the free corrosion potential values (Ecorr at o.c.p.), considered as electrochemical noise (EN), were correlated with the stainless steel pitting corrosion in sea water. Ecorr fluctuation analysis was carried out using the power spectral density (PSD) vs frequency. Figure 1 presents the initially changes of Ecorr with time vs frequency in bilogarithmic scale. For the first three days, the PSD slopes present a negative β exponent (β > 1) at lower frequencies [0.002 – 0.05 Hz], indicating a release of spontaneous energy from the steel surface (corrosion). However, at major frequencies β tends to values close to zero (0.12 – 0.07). At later stages the PSD slopes show a unique value close to zero (0.02 – 0.06), in all range of frequencies [0.002 – 1 Hz]. The exponent β is associated with persistent processes (forces) in data series (216) over time. The calculated Hurst coefficient based on β values suggested that initially the localized corrosion process occurs with the contribution of fractional Brownian motion (fBm) and fractional Gaussian noise (fGn). After the first three days, the Ecorr fluctuations were only dominated by fGn (H≈0.5), which corresponds to the special case when the corrosion occurs at the border between anti-persistent (H<0.5) and persistent (H>0.5) processes. The Ecorr fluctuations were correlated with the data surfaces provided by SEM-EDS and XRD.

Figure 1
Modification of Bbituminous Coatings to Prevent Stress Corrosion Cracking of Carbon Steel
Authors: Ignatenko Vasiliy Eduardovich , Maleeva Marina Alekseevna , Petrunin Maxim Andreevich , Shapagin Alexey Viktorovich , Sherbina Anna Anatol'evna 
Published: February 2020

Stress corrosion cracking (SCC) is the most dangerous kind of pipelines corrosion. The SCC appears on the stressed metal due to contact with aggressive media through the rupture of polymer coating. Inhibition of the SCC is one of the urgent tasks of corrosion protection of underground pipelines. The research reports the method of inhibiting the SCC of pipe steels by modification of polymer protective coatings.
With help of slow strain rate test (SSRT) the effect of general corrosion inhibitors and surfactants on the propensity X70 pipe steel to the SCC in aggressive electrolytes has been investigated. The vinyl-containing silane (VS) is shown to be an effective inhibitor of SCC of steel.
The VS has been proposed as a modifying additive to a bitumen coating (DEKOM-GAZ type). Modification of coating should provide both satisfactory adhesion and exit of the SCC inhibiting compounds to electrolyte under film and their adsorption onto the metal surface in the case of mechanical damage or loss of adhesion.
Peel shear test at an angle 90° away from steel plate has been used for evaluation of adhesive properties of modified coating. It has been shown that the additive of the VS does not impair the adhesion of the protective coating. Using FTIR microscopy output of the inhibitor molecules from the polymer matrix to solution and their adsorption onto the metal surface was evaluated. The aqueous extract obtained by exposure of the polymer coating with the addition of the VS in contact with water for 30 days has been investigated. IR-spectra analysis showed that predominantly the VS goes from the coating into solution and adsorbs on the metal surface.
Thus the modified polymer coating, the use of which will prevent the development of SCC of carbon steel, has been developed.
Control the Corrosion of Magnesium for Implant Application By Hydrothermally Deposited Biodegradable Calcium Phosphate Coating
Authors: Kaabi Falahieh Asl Sara , Nemeth Sandor , Tan Ming Jen 
Published: February 2020

The corrosion protection of hydrothermally deposited calcium phosphate coatings on AZ31 magnesium alloy was studied in simulated body fluid (SBF) solution for their potential use as biodegradable implants. The coating mainly consisted of bioresorbable monetite phases. Potentiodynamic and electrochemical impedance spectroscopy (EIS) confirmed that the coatings provided varying levels of corrosion protection depending on the coating deposition temperature. By increasing the deposition temperature and corresponding growth in coating thickness the corrosion current density of the coated magnesium was 10,000 fold lower compared to the bare metal; indicating significantly enhanced corrosion performance of Mg substrate, reaching the corrosion protection requirement for magnesium implant. The barrier effect of Ca-P layers was further supported by the observed magnitude of anodic and cathodic Tafel slopes. Coated samples displayed much larger slopes than bare Mg substrate.
EIS results showed that the size of capacitance loops and the absolute impedance value (|Z|) increases. By increasing the deposition time the corrosion mechanism was changed as a result of partial delamination of top surface of coating. In agreement with the electrochemical experiments, immersion tests in SBF also indicated large improvement in corrosion protection as the mass loss was reduced almost three times when coating was applied as compared to the bare metal.
The uncoated Mg substrate undergoes severe and non-uniform corrosion after 28 days immersion in SBF solution; while, the coated samples displayed intact coating and no obvious pits were observed on the coating surface.
The described biocompatible and biodegradable coatings significantly improved corrosion resistance of Mg substrate and can be promising candidate for biomedical application.
Keywords: Magnesium, Calcium-Phosphate coating, Corrosion resistance, EIS
Protein Interactions with Corroding Metal Surfaces
Authors: Virtanen Sannakaisa 
Published: February 2020

Low-corrosion resistant metals, such as Mg or Fe based alloys, have been in the focus of intensive research activities in recent years to be used in biodegradable implants. A general challenge is to tailor the materials and surfaces to achieve the desired and controlled corrosion rate for the targeted applications. A further challenge is to elucidate the influence of the complex biological environment on the corrosion mechanisms of these materials. A vast majority of the studies in this field have been carried out on Mg based materials; far less attention has been given to Fe. A comparison of the behavior of Fe and Mg based alloys in simulated biological environments is on one hand side of practical interest in view of possible biomedical applications of these materials. Moreover, from mechanistic point of view, a direct comparison may aid in elucidating mechanisms of interactions between the constituents of the biological environment and the corroding metal surfaces in more detail. In the present study, we are investigating the influence of proteins on the corrosion behavior of Mg and Fe by electrochemical and surface analytical techniques. Proteins in solution can have multiple effects on corrosion reactions: on one hand side, protein adsorption layers can block electrochemically active surface sites and therefore slow down corrosion. Protein adsorption will be influenced by the surface chemistry of the metals (e.g., wettability, type of oxides/hydroxides formed on the surface, and the resulting surface charges) - therefore different interactions may be expected for Mg and Fe. On the other side, complexation of metal cations can take place by proteins (and amino acids), thereby reducing the free cation concentration and possibly accelerating corrosion. Also this effect depends on the nature of the metal cations; for Fe and Mg dissolution products different strength of interactions can be expected. Electrochemical studies indeed indicate very different interactions of proteins (bovine serum albumin, BSA) on Mg as compared with Fe. For Mg, inhibition of corrosion in presence of albumin in solution can be observed for short-term experiments. For Fe, a slight increase of corrosion by addition of albumin in solution takes place. In general, the influence of BSA on the corrosion behaviour of Mg is much stronger than that observed for Fe. Surface analytical studies (XPS and ToF-SIMS) demonstrate stronger adsorption of albumin on Mg than on Fe. Moreover, protein adsorption on Mg and Fe varies for different proteins (for instance: albumin vs. lysozyme). Possible mechanisms and critical factors of protein interactions with corroding Fe and Mg surfaces will be discussed.
Effect of Boron Addition on Oxide Scale Formation of Ni-Base Superalloys
Authors: Nowak Wojciech , Jałowicka Aleksandra , Young David John , Naumenko Dmitry , Quadakkers Willem J. 
Published: February 2020

Ni-base superalloys are commonly used as construction materials for high temperature components e.g. in the hottest sections of aero engines and industrial gas turbines due to a combination of excellent creep and high-temperature oxidation resistance at elevated temperature. Apart from major alloying elements such as Cr, Co, Al, Mo, W, Ti, modern Ni-based superalloys contain minor (between 0.01 and 1 at.%) additions of elements such as Hf, Zr or B for obtaining improved mechanical properties, in particular grain boundary strengthening. However, these minor elements also form thermodynamically very stable oxides and can therefore participate in the oxidation process. Whereas several investigations are available on the effect of Hf and Zr additions on the oxidation behaviour of high temperature alloys, hardly any publications deal with studies related to the effect of B additions on oxide formation mechanisms.
In the present investigation the air oxidation behaviour of two commercially available B containing Ni base alloys (Rene80, CM247) was studied at temperatures in the range 850°C to 1050°C. After various exposure times up to 100h the oxidized samples were investigated with a number of analysis methods, including glow discharge optical emission spectroscopy (GD-OES), optical and scanning electron microscopy (SEM combined with EDX/WDX and EBSD) as well as X-Ray diffraction.
B was found to become incorporated into the oxide scale whereby the participation in the oxidation process strongly depended on alloy composition. The oxidation of B resulted in its depletion from the bulk alloy and was found to be dependent on the exposure conditions, being stronger at higher exposure temperatures and longer exposure times. A modelling approach is presented to correlate B incorporation in the surface oxidation process with its depletion in the bulk alloy.