Basicities and transformations of pyrylium and pyridinium salts containing p-aminophenyl substituents

On the basis of the measured basicity constants of pyrylium and pyridinium salts containing p-aminophenyl substituents it is shown that the positive charge in the pyrylium cation is considerably higher than in the pyridinium cation. The constants of the pyrylium and pyridinium substituents, which show that the magnitude of the electronic effect of the pyrylium ring is considerably higher than that of the pyrydinium ring, were calculated. The reaction of the indicated pyrylium salts with some electrophilic and nucleophilic reagents was examined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1025–1028, August, 1976.     

5-amino-3,4-dihydro-2h-1,2,4-triazole-3-thiones. synthesis and chemosensor properties

The reaction of 4-arylalkyl- and 4-arylthiosemicarbazides with aroyl isothiocyanates gave substituted 1,2-bis(thiocarbamoyl)hydrazines, which readily cyclize to give previously unreported 4-aroyl 5-arylalkyl- and 4-aroyl-5-arylamino-2H-1,2,4-triazole-3-thiones, respectively. A spectral study of 9-anthrylmethylthiosemicarbazides and derived dihydrotriazolethione indicated the chemosensor activity of these compounds relative to a cation series.     

Chemosensor properties of mono- and bisthioureas based on 9-anthrylmethyl-substituted alkylamines and diamines

Mono- and bisthioureas were synthesized based on N-(9-anthrylmethyl)-substituted alkylamines and diamines. Their luminescent and complexing properties were studied by the electronic, IR, and NMR ¹H spectroscopy. N-(9-Anthrylmethyl)-N-(6-{9-anthrylmethyl[(phenylamino)carbothioyl]amino}hexyl)-N′-phenylthiourea was shown to be a highly effective fluorescent chemosensor for Hg²⁺ cations.     

Interfacial composition, structural parameters and thermodynamic properties of water-in-oil microemulsions

The formation and structural characteristics of water-in-oil microemulsions comprising hexadecylpyridinium chloride (CPC), alkanols (C₄–C₆) and alkanes (C₅, C₈–C₁₀) have been investigated by the method of dilution. The compositions of the surfactant and the cosurfactant in the interfacial region (interphase) of the microemulsion droplets have been determined. The thermodynamics of transfer of the cosurfactants (alkanols) from the continuous oil (alkane) phase to the interface have been evaluated from dilution measurements at different temperatures. The structural parameters, radii of the droplet and the waterpool, aggregation numbers of CPC and the alkanols in the interphase of a droplet, and the nanoparticle density of solution have been estimated assuming monodispersity of the droplets. The thermodynamics and structural parameters have been examined in terms of the chain lengths of the alkanols and alkanes. Received: 12 September 2000 Accepted: 27 October 2000     

Photochemical properties and structures of substituted norbornadienes

The spectral and photochemical properties of 3-phenylnorbornadiene-2-(N-phenyl)aldimine and 3-phenyl-2-(2,2-dicyanovinyl)norbornadiene have been studied, and their structures have been established by X-ray analysis. It was found that the C(2)=C(3) bonds in these compounds are longer than those in unsubstituted norbornadienes. It was established that long-wave absorbtion boundaries and quantum yields of the photoisomerization of 2,3-disubstituted norbornadienes to give the corresponding quadricyclanes increase as the C(2)=C(3) bond length increases and as the bond order decreases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–508, March, 1995.This work was supported by the International Science Foundation (grant No. RNC 000).     

The proapoptotic G41S mutation to human cytochrome c alters the heme electronic structure and increases the electron self-exchange rate

The naturally occurring G41S mutation to human (Hs) cytochrome (cyt) c enhances apoptotic activity based upon previous in vitro and in vivo studies, but the molecular mechanism underlying this enhancement remains unknown. Here, X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations have been used to identify the structural and electronic differences between wild-type (WT) and G41S Hs cyt c. S41 is part of the hydrogen bonding network for propionate 7 of heme pyrrole ring A in the X-ray structure of G41S Hs cyt c and, compared to WT, G41S Hs cyt c has increased spin density on pyrrole ring C and a faster electron self-exchange rate. DFT calculations illustrate an electronic mechanism where structural changes near ring A can result in electronic changes at ring C. Since ring C is part of the solvent-exposed protein surface, we propose that this heme electronic structure change may ultimately be responsible for the enhanced proapoptotic activity of G41S Hs cyt c.     

Structure of indoline spiropyrans containing a fused coumarin fragment: Quantum-chemical investigation

In order to examine the way of fusion of the coumarin fragment to the 2H-pyran part of indoline spiropyrans the relative stability was estimated of the cyclic and merocyanine forms by means of calculations in the framework of DFT in B3LYP/6-31G(d,p) approximation. In agreement with the experimental data the relative stabilization of the spirocyclic isomer correlates with the length of the bond where the fusion occurs.