A. Yu. Tsivadze

Orthophosphoric Acid-;N,N-Dimethylformamide System: IR Study

Interactions in the orthophosphoric acid (H3PO4)-;N,N-dimethylformamide (DMF) system are studied by IR Fourier spectroscopy. A mechanism of interaction between the H3PO4 and DMF molecules was proposed on the basis of the results and the earlier reported viscosimetry data for this system.

Evidence for large hydrogen storage capacity in single-walled carbon nanotubes encapsulated by electroplating Pd onto a Pd substrate

We report a study of hydrogen storage in an alternative material, representing single-walled carbon nanotubes (SWCNTs) encapsulated by thin Pd layers onto a Pd substrate. A synergetic effect resulting in combination of the Pd and the SWCNTs properties with regards to hydrogen has been achieved. Adding SWCNTs increases the H{sub 2} capacity of the Pd-SWCNT composite by up to 25% relative to Pd metal alone under electrochemical loading. This results in a storage capacity of 8-12 wt %. with regard to the added SWCNTs.

Crown-substituted phthalocyanines—components of molecular ionoelectronic materials and devices

This review summarizes the synthetic approaches towards oxa-crown-substituted phthalocyanines (CRPc’s) including various metal complexes of s-, p-, d-, and f-elements. The template cyclotetramerization of phthalonitriles and direct metalation pathways for synthesis of target compounds are discussed and compared. It is demonstrated that obtained results have contributed to coordination, supramolecular, and materials chemistry of phthalocyanines in general. An analysis of the results published to date reveals the challenges of these compounds for their use in high-tech applications.

Photoelectric, nonlinear optical, and photorefractive properties of polymer composites based on supramolecular ensembles of Ru(II) and Ga(III) complexes with tetra-15-crown-5-phthalocyanine

Techniques of the production of polymer nanocomposites based on tetrapyrrole compounds with photoelectric, nonlinear optical, and photorefractive properties are considered. Supramolecular ensembles of Ru(II) and Ga(III) complexes with tetra-15-crown-5-phthalocyanine are found to form upon the deposition of thin films from tetrachloroethane solutions that have undergone several cycles of heating followed by slow cooling. The surface formation of supramolecular ensembles is studied with the use of atomic force microscopy. The assemblage is found to give rise to photoelectric and photorefractive sensitivity in the near-infrared range (measurements were carried out at 1064 and 1550 nm). The quantum yield of thermalized electron-hole pairs at 1064 nm in composites of polyvinyl carbazole and assembled Ga(III) complexes is 20 times as high as that in composites based on Ru(II) complexes. The largest two-beam coupling gain coefficient at 1064 nm (Γ = 120 cm−1 at E0 = 120 V/μm) was also observed for the Ga(III)-complex-containing composite. The third-order dielectric molecular susceptibility measured in tetrachloroethane solutions of the complexes weakly depends on the nature of the central atom and its axial neighborhood and falls in a range of γ = 4−5.2 × 10−32 esu.

Fine structure of polymeric compositions based on latexes modified by water-soluble phthalocyanine

The data of the atomic force microscopy of films and coatings based on the water-soluble polymer binders modified with water-dispersion phthalocyanine (WDP) are considered. In the formation of films from a latex polymer with a low glass-transition point (−17°C) and both nonmodified and phthalocyanine-modified latex particles completely coalesce, which manifests in the high smoothness of the surface and the WDP distribution over the whole volume of the polymer. The surface roughness of an elastic polymer with a glass-transition point below 25°C is observed in the case of polyalkyl (meth)acrylate films that contain WDP. Here, a continuous network of latex particles that contact each other is clearly seen. This type of structure appears at a dispersion-phase WDP concentration of up to 10−3 to 10−2 mol/l when the fluoride is homogeneously distributed in the latex polymer. During the film formation, WDP is localized on the particle surfaces due to the interaction between its amine groups and carboxyl groups of the polymer surface.

Synthesis and structure of heteroleptic triple-decker neodymium, europium, holmium, erbium, and ytterbium crown phthalocyaninates

Two series of heteroleptic crown-substituted tris(phthalocyaninate) complexes (Pc)Ln[(15C5)4Pc]Ln(Pc) and [(15C5)4Pc]Ln[(15C5)4Pc]Ln(Pc), where 15C5 is 15-crown-5, (Pc2−) is the phthalocyaninate dianion, Ln = Nd, Eu, Ho, Er, and Yb, were prepared by the reaction of tetra-15-crown-5-phthalocyanine H2[(15C5)4Pc] with the corresponding lanthanide acetylacetonates and lanthanum bis(phthalocyaninate) La(Pc)2, which was used as a phthalocyaninate dianion donor. The composition and structure of the synthesized complexes were confirmed by MALDI TOF mass spectrometry, UV-Vis absorption spectroscopy, and 1H NMR. Complete assignment of the proton resonance signals of the paramagnetic lanthanide complexes was based on analysis of lanthanide-induced shifts.

Laser-ellipsometric monitoring of corrosive attack

The problems under consideration are related to the development and practical application of laser, reflectometric, and ellipsometric methods of diagnostics of corrosion damage both at the micro and macro level. The following basic methods of probe laser and ellipsometric studies of corrosion electrochemical processes are considered: automatic and return-path ellipsometry, microscopic and video ellipsometric techniques, methods of light scattering, fluctuation and noise reflectometry, probe noise ellipsometry, microlocalized electrochemical processes, remote ellipsometry, laser and spectral tomography, and information optical 3D technologies for reconstructing the 3D structure of heterogeneous near-electrode layer. The primary attention was focused on the problems of application of laser and ellipsometric methods in the practice of real corrosion electrochemical studies.

Fundamental problems of lithium-ion rechargeable batteries

A brief review of the main scientific problems related to the improvement of lithium-ion rechargeable batteries and works carried out in the field at the Frumkin Institute of Physical Chemistry and Electrochemistry is given.

Orientation-induced redox transformations in Langmuir monolayers of double-decker cerium bis[tetra-(15-crown-5)-phthalocyaninate] and multistability of its Langmuir-Blodgett films

The spectral, electrochemical, and optical properties of Langmuir-Blodgett films (LBFs) and cast films from a solution of new double-decker cerium bis[tetra-(15-crown-5)-phthalocyaninate] (Ce(R4Pc)2) are studied. Based on analysis of compression isotherms and quantum-chemical calculations, schemes of the organization of Ce(R4Pc)2 molecules at different states of its monolayers are proposed. Correlation dependences are determined in order to relate the optical and electrochemical characteristics of monolayers and LBFs of sandwich-type lanthanide phthalocyaninates to the ionic radii of their metal centers. The valent state of Ce ions in a monolayer-forming complex is determined, and a sequence of redox transformations occurring in LBF uppon appliance of a potential is proposed, one of the transformations being associated with the Ce3+/Ce4+ redox transition. Orientation-induced intramolecular electron transfer is revealed in the planar supramolecular system. It is shown that, during the formation of a monolayer from a Ce(R4Pc)2 solution, a tetravalent metal center passes to a trivalent state. Monolayer compression to a high surface pressure reverts the complex to the electronic state typical of the solution. The reversible transformations observed upon the monolayer compression result from intramolecular electron transfer from the 4f-orbital of Ce to the phthalocyanine ring and backwards. The high operation rate and the reversibility of switching between the stable states, which are determined by means of the surface plasmon resonance technique, upon a stepwise change in the electrode potential within the range of 200–850 mV may underlie the development of optoelectronic systems. With a large number of molecules in a stacking aggregate, changes in the distance between the decks of the complex that occur with changes in the oxidation level of the metal center can substantially modulate the sizes of molecular ensembles. A supramolecular device capable of performing mechanical work can be developed based on this effect.

Photoelectric, nonlinear optical, and photorefractive properties of composites based on poly(N-vinylcarbazole) and gallium phthalocyaninate

Poly(N-vinylcarbazole) layers containing tetra-5-crown-5-gallium phthalocyaninate (R4Pc)Ga(OH) are shown to possess photoelectric and photorefractive sensitivity at a wavelength of 1064 nm. This effect is associated with the formation of supramolecular ensembles of (R4Pc)Ga(OH) molecules with electronic optical absorption in the near-IR range and nonlinear optical properties. For the composite containing 5 wt % (R4Pc)Ga(OH) supramolecular ensembles, the dependence of the quantum efficiency of mobile-charge photogeneration on electric field E0 is well fit by the Onsager equation expanded to E03 at a quantum yield of electron-hole pairs of φ0 = 0.9 s with an initial separation radius of r0 = 9.8 A susceptibility χ(3) equal to 1.85 × 10−10 esu is measured via the well-known method of electric-field-induced second-harmonic generation. Two-beam-coupling gain coefficient Γ is found to be 80 cm−1 at E0 = 120 V/μm.