Hetarylethylene derivatives of 2,5-diaryloxazoles and 2,5-diarloxadiazoles and their luminescence and scintillation properties

A number of new organic luminophores were synthesized via the Wittig reaction from 2-(4-bromomethylphenyl)-5-phenyloxazole or 2-(4-bromomethylphenyl)-5-phenyl-1,3,4-oxadiazole and various heterocyclic aldehydes containing a thiophene ring.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1267–1270, September, 1986.     

Polarographic examination of 5-aryl-2-(2-thienyl)-oxazoles and -1,3,4-oxadiazoles

The polarographic behavior of 5-aryl-2-(2-thienyl)oxazoles and -1,3,4-oxadiazoles has been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1550–1552, November, 1986.     

Spectral and quantum-chemical study of some heteroanalogs of 1,4-bis(5-phenyl-2-azolyl)benzenes

The effect of structural changes in the molecules of thiophene and furan analogs of 1,4-bis(5-phenyl-2-azolyl)benzenes on their electronic spectra was studied by the MO LCAO method within the -electron approximation.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 817–821, June, 1991.     

Synthesis and spectral-luminescence properties of carbonyl derivatives of 2-(2-thienyl)-5-aryloxazoles

Electrophilic substitution reactions in the 2-(2-thienyl)-5-aryloxazole series and the spectral-luminescence properties of the compounds obtained were investigatedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 839–844, June, 1989.     

A New Fluorescent Squaraine Probe for the Measurement of Membrane Polarity

The present study was undertaken to evaluate the sensitivity of newly synthesized squaraine dye 1 to the changes in lipid bilayer physical properties and compared it with the well-known dye 2. Partitioning of the dye 1 into lipid bilayer was found to be followed by significant increase of its fluorescence intensity and red-shift of emission maximum, while intensity of the dye 2 fluorescence increased only slightly on going from aqueous to lipidic environment. This suggests that dye 1 is more sensitive to the changes in membrane properties as compared to dye 2. Partition coefficients of the dye 1 have been determined for the model membranes composed of zwitterionic phospholipid phosphatidylcholine (PC) and its mixtures with positively charged detergent cetyltrimethylammonium bromide (CTAB), anionic phospholipid cardiolipin (CL), and sterol (Chol). The spectral responses of the dye 1 in different liposome media proved to correlate with the increase of bilayer polarity induced by Chol and CL or its decrease caused by CTAB. It was concluded that dye 1 can be used as fluorescent probe for examining membrane-related processes.     

Theoretical study of the pathway for diazine ring formation in a series of 4-dimethylaminonaphthalic acid derivatives under Vilsmeier-Haack reaction conditions

Using the semiempirical quantum-chemical PM3 method, we have studied the formation of a quaternized diazine ring in a series of 4-dimethylaminonaphthalic acid derivatives under Vilsmeier-Haack reaction conditions. We have established that the reaction may occur via a two-step cycloisomerization of the intermediate Vilsmeier adduct, through six-center cyclic transition states. Institute of Single Crystals, National Academy of Sciences of Ukraine, 60 Prospekt Lenina, Khar'kov 310001, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 36, No. 4, pp. 201–205, July–August, 2000.     

Dimethylamino-substituted 7H-Benzo[de]pyrazolo[5,1-a]isoquinolin-7-ones and Their Behavior under Vilsmeier-Haack Conditions

The behavior of dimethylamino-substituted 7H-benzo[de]pyrazolo[5,1-a]isoquinoline-7-ones, synthesized for the first time, under conditions of the Vilsmeier-Haack reaction. It has been shown that, on heating with POCl₃ and DMF, they are converted by electrophilic substitution at the position ortho to the dimethylamino group, followed by cyclization of the iminium adduct to a quinazolinium salt. When an acetyl group is present, the Arnold reaction, leading to the formation of a chloroaryl, accompanies the heterocyclization. The rates and proportion of the reaction products depend on the position of the dimethyl groups relative to the pyrazole ring.     

Configuration of 2-(2-thienyl)-5-aryloxazoles in their ground and excited states

The electronic absorption and emission spectra of a series of 2-(2-thienyl)-5-aryloxazoles in solutions, vapors, and matrices (ethanol-ether, 77 K) have been studied, and the fluorescence quantum yields have been determined. The basicity constants in aqueous solutions in the ground state have been measured spectrophotometrically. The set of spectroscopic data indicate that the configuration of the 2-(2-thienyl)-5-aryloxazoles in the ground state is nearly planar and is practically independent of the temperature and the state of aggregation. Conversely, in the excited state the configuration of these molecules is generally nonplanar and depends on external factors.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 382–387, March, 1989.