Towards stabilization of the potential response of Mn(III) tetraphenylporphyrin-based solid-state electrodes with selectivity for salicylate ions

Journal of Solid State Electrochemistry - We report a new type of solid-state electrode (type I) of a simple design with polyvinyl chloride membranes based on Mn(III) tetraphenylporphyrin and with...     

Study of oxidized states in copolymers of ferrocene by the method of γ-resonance spectroscopy

Russian Chemical Bulletin -     

The properties of graphite electrodes modified by the quinone-hydroquinone system

The standard states of quinone and hydroquinone were selected to be those of pure substances, which allowed us to introduce the solubility product of quinhydrone. This selection of the standard state made it possible to interpret both the interval and direction of changes in the oxidation potential of graphite electrodes whose pores were filled by these substances in aqueous solutions with a fixed acidity.     

Basicity of para-substituted tetraphenylporphyrins studied by two-phase spectropotentiometric titration

The basicity constants of a series of para-substituted tetraphenylporphyrins have been determined by two-phase spectrophotometric titration with pH monitoring in the chloroform-aqueous electrolyte solution system; the pH ranges of prevailing of the dication and the neutral forms of the porphyrins have been estimated. With introducing the donor substituents at the para-position of phenyl fragments of porphyrins, the compound basicity increases. Ionization constant of the pyrrole nitrogen atoms depends on the donor-acceptor properties of the substituents according to the Hammett equation. Basing on the derived dependence, theoretical basicity constants of the para-substituted porphyrins bearing strongly donor groups have been predicted.     

Application of solvation excess concept to solutions of 3 : 1 and 1 : 3 electrolytes

Data on water activity in solutions of a series of 3 : 1 and 1 : 3 electrolytes [AlCl₃, Al(NO₃)₃, LaCl₃, La(NO₃)₃, H₃PO₄, NaH₂PO₄] have been generalized in the frame of solvation excesses concept. Solvation excess reflects the distribution of the selected structural elements (ions or solvent particles) in the solution. The computed values have demonstrated the opposite contributions of ion association and hydration of ions and ion associates. Solvation excess concept allows determination of water molecules fraction constituting the excess at ions and their associates. The comparison of results obtained with different choice of model structural units has shown the electrolyte concentration ranges of validity of the respective models.     

Basicity of octa- and dodecamethyl-substituted tetraphenylporphyrins by phase-transfer spectral potentiometric titration

Phase-transfer potentiometric titration with potentiometric pH control in the system chloroform-aqueous electrolyte solution was used to determine basicity constants for octamethyl-substituted tetraphenylporphyrins. The pH ranges were determined, where the dicationic form of octa- and dodecamethylsubstituted tetraphenylporphyrins is prevailing. It was shown that the basicity of tetraphenylporphyrins is increased by methyl substitution of β-hydrogens (formation of octamethyl-substituted tetraphenylporphyrins). Further methylation of the four central nitrogen atoms of the porphyrin (formation of dodecamethyl-substituted tetraphenylporphyrins) extends the dication stability pH range to 12.     

Solvation Excess of Urea over Water in Humic Acid in Three-Component Solutions Saturated with the Biopolymer

Humic acids were extracted from brown coals of the Kara-Keche deposit (Kyrgyzstan) and characterized. The solubility of humic acid in aqueous urea solutions was studied. The solvation excess of urea over water on humic acid in solution was calculated. The possibility of simultaneous binding of urea molecules on three independent centers of humic acids was shown. An estimation of humic acid molecular dimensions in aqueous urea solutions is given.     

A Synthetic Fluorescent Mitochondria‐Targeted Sensor for Ratiometric Imaging of Calcium in Live Cells

Ca²⁺ handling by mitochondria is crucial for cell life and the direct measure of mitochondrial Ca²⁺ concentration in living cells is of pivotal interest. Genetically‐encoded indicators greatly facilitated this task, however they require demanding delivery procedures. On the other hand, existing mitochondria‐targeted synthetic Ca²⁺ indicators are plagued by several drawbacks, for example, non‐specific localization, leakage, toxicity. Here we report the synthesis and characterization of a new fluorescent Ca²⁺ sensor, named mt‐fura‐2, obtained by coupling two triphenylphosphonium cations to the molecular backbone of the ratiometric Ca²⁺ indicator fura‐2. Mt‐fura‐2 binds Ca²⁺ with a dissociation constant of ≈1.5 μm in vitro. When loaded in different cell types as acetoxymethyl ester, the probe shows proper mitochondrial localization and accurately measures matrix [Ca²⁺] variations, proving its superiority over available dyes. We describe the synthesis, characterization and application of mt‐fura‐2 to cell types where the delivery of genetically‐encoded indicators is troublesome.     

The use of the concept of solvation excesses for studying the mutual distribution of solution component particles in the H<Subscript>2</Subscript>O-KCl-NaCl and H<Subscript>2</Subscript>O-KNO<Subscript>3</Subscript>-NaNO<Subscript>3</Subscript> systems

The data on component activities and salt solubilities were analyzed to determine solvation excesses in the H₂O-KCl-NaCl and H₂O-KNO₃-NaNO₃ systems. Some rules governing the solvation of ions were discussed.