V. V. Shamanin

Organic materials for photovoltaic and light-emitting devices

Materials for organic photovoltaic cells and light-emitting devices are reviewed. Dye-sensitized systems represent the most studied of these materials as they offer high efficiency of photoelectric energy conversion. Systems demonstrating efficient luminescence were identified; they are based on conjugated polymers, complexes of rare-earth elements with organic ligands, and dyes. To achieve efficient photoelectric conversion, different types of sensitizing dyes will be tested. Phthalocyanines and pentacenes are of special interest. Phthalocyanines are the most promising materials: they are easily synthesized and nontoxic, and their electric characteristics are widely investigated. Harnessing the unique electron-acceptor properties of the C60 molecule, one can attain considerable enhancement in the efficiency of solar-energy conversion into electricity. Organic photovoltaic cells are often made on the basis of aromatic and heterocyclic polymers—poly(p-phenylene-vinylene), polyanilines, polypyrroles, and polythiophenes. Organic photoconducting materials offer high photosensitivity and low dark current. They are readily available and can be easily deposited on a substrate, which make them suitable for the fabrication of relatively cheap photovoltaic cells.

Aggregation in Hydroxylated Endohedral Fullerene Solutions

This paper presents some useful results filling the gap in the knowledge about the aggregation of hydroxylated endohedral fullerene Gd@C82(OH)18(contrast agent for magnetic resonance imaging) in aqueous solutions at different pH. A supramolecular ordering study by small-angle neutron scattering has shown that fullerenols exist in cluster form (correlation radius RC ∼ 20–30 nm, fractal dimension D). At pH increasing from 4–5 to 7–8 there was observed a transition from dense branched structures (D ∼ 2.5) to rare coil-like objects (D ∼ 1.5).

Tautomerism and conformational isomerism of mercaptoacetylhydrazones of aliphatic and aromatic aldehydes

Mercaptoacetylhydrazones of aliphatic and aromatic aldehydes exist in the solutions as tautomeric mixtures of open-chain and cyclic 1,3,4-thiadiazine forms. The linear hydrazone form consists of a set of isomers due to the configurational and conformational isomerism. At growing bulk of the alkyl substituent at the C=N bond of the aliphatic aldehydes derivatives decreases the fraction of the cyclic tautomer; therewith the logarithms of the constants of the chain-ring tautomeric equilibrium correlate with the steric constants of the alkyl substituents. In the series of the aromatic aldehydes mercaptoacetylhydrazones the linear tautomer prevails, and the equilibrium position is insignificantlyt affected at variation of the electronic characteristics of the substituents in the aromatic ring.

MRI-Contrasting System Based on Water-Soluble Fullerene/Gd-Metallofullerene Mixture

The gadolinium endometallofullerene/empty fullerene hydroxylated mixtures were prepared and studied as MRI-contrasting agents. The mixtures were prepared with metallofullerene enrichment of more than 80 mol.% by simple liquid extraction. The hydroxylation was performed by H2O2 oxidation at elevated temperature. Nanoaggregation of mixed fullerenes in water solution was studied by SANS. It was observed that at pH = 7 the cluster correlation diameter is 25 nm. NMR tomography in-vivo reveals that contrasting action of hydroxylated gadofullerene mixtures is 15–30 times its commercial “Gadovist” contrasting agent.

Correlation dependences in infrared spectra of metal phthalocyanines

Metal-phthalocyanine (MPc) complexes CoPc, CuPc, CuPcCl15–16, CuPc(4-NO2-5-OPh)4, CuPc(4-CH2-phthalimide)4, CuPc(4-NO2-5-NHPhBr)4, PdPc, MgPc, PbPc, EuOAcPc, SmOAcPc, SmPc2, and YOAcPc were obtained and studied using IR spectroscopy. The correlation between the shift of the absorption band maximum in the range of 1100–1600 cm−1 and the atomic radius of template metal is found. It is shown that the planarity of the macrocycle of peripherally substituted CuPc can be estimated from the characteristics of the IR spectra.

Photosensitive structures based on single-crystal silicon and phthalocyanine CuPc: Fabrication and properties

Vacuum thermal deposition of phthalocyanine CuPc onto the surface of crystalline silicon and subsequent magnetron sputtering of ZnO:Al are used to form n-ZnO:Al-p-CuPc-n-Si photosensitive structures for the first time. The highest photosensitivity of these structures SUm≈20 V/W is attained if the ZnO side of the structure is illuminated and is observed in the photon-energy range 1–3.2 eV at T=300 K. An induced photopleochroism is observed if the linearly polarized light is incident obliquely on the ZnO side; the magnitude of the photopleochroism oscillates as a result of the interference of linearly polarized light in the ZnO film. It is concluded that the suggested structures have prospects for use in broadband photoconverters of natural light and in rapidly tunable photoanalyzers of linearly polarized light.

Structure of the condensation products of 3-sulfanylpropionic acid hydrazide with aldehydes, ketones, and aldoses

Condensation products of aliphatic aldehydes with 3-sulfanylpropionic acid hydrazide exist in solution as mixtures of linear hydrazone and cyclic 1,3,4-thiadiazepine tautomers. Hydrazones derived from 3-sulfanylpropionic acid hydrazide and aromatic aldehydes and ketones have mostly linear structures of different stereoisomers arising from Z-E isomerism with respect to the double C=N bond and restricted rotation about the C(O)-N bond. Condensation products of 3-sulfanylpropionohydrazide with a series of aldoses give rise to ring-chain-ring tautomeric equilibrium between α,β-isomeric pyranose structures, open-chain aldose hydrazone tautomer, and two diastereoisomeric seven-membered cyclic 1,3,4-thiadiazepine forms.

Ring-chain tautomerism of 2-aryl-6-oxohexahydropyrimidine-4-carboxylic acid sodium salts

It was shown by 1H and 13C NMR spectroscopy that the 2-aryl-6-oxohexahydropyrimidine-4-carboxylic acid sodium salts existed in D2O solution as a tautomeric mixture of cyclic and linear forms. The cyclic form consisted of two (2RS,4S)-stereoisomers, differing in the aryl substituent configuration at the pyrimidine ring C-2 atom.

Structure of products of aldoses condensation with thioglycolic acid hydrazide

Condensation products of thioglycolic acid hydrazide with aldoses (L-arabinose, D-xylose, L-rhamnose, D-galactose, D-glucose, D-mannose) exist in the D2O solution as a tautomeric mixture of α,β-pyranose form and six-membered 1,3,4-thiadiazine form present as two diastereomers.

Structure of aldose condensation products with 2-hydroxyand 2-sulfanylbenzohydrazides

The structure of the condensation products of 2-hydroxy- and 2-sulfanylbenzohydrazides with a series of aldoses (L-arabinose, D-ribose, L-ramnose, D-galactose, D-glucose, D-mannose) was studied by 1H and 13C NMR spectroscopy. The condensation products of monosaccharides with 2-hydroxybenzohydrazide in DMSO-d6 solution exist as equilibrium mixtures of linear hydrazone and cyclic pyranose and furanose forms, the cyclic tautomers being represented by two stereoisomers (α- and β-anomers). The aldose condensation products with 2-sulfanylbenzohydrazide in the crystalline state have cyclic 1,3,4-benzothiadiazepine structure, while in DMSO-d6 solution they undergo complete or partial isomerization into cyclic pyranose tautomer.