Structure of sterically hindered aryl derivatives of five-membered nitrogen containing heterocyclicortho-analogs of POPOP

Дорошенко, А. О.; Patsenker, L. D.; Баумер, В. Н.; Chepeleva, L. V.; Vankevich, A. V.; Kirichenko, Alexander; Yarmolenko, Sergey; Scherschukov, V. M.; Mitina, V. G.; Ponomaryov, O. A.

doi:10.1007/bf01003759

Cited by 15 publications

(10 citation statements)

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“…[19] From phenacyl chloride, the first two steps yielded ammonium salts 2 via the hexamethylene tetramine adduct 1 (Dele Â pine reaction). [20] In the presence of a base (pyridine [21] or aqueous sodium carbonate [22] ) 2 reacted with 4-substituted benzoic acid chlorides to form amides 3. Dehydration thereafter led to R-substituted PPOs: R F (4 a), Cl (4 b), Br (4 c), CH 3 (4 d).…”

Section: Resultsmentioning

confidence: 99%

“…Dichloromethane was also less toxic. In the preparation of 3 a ± 3 d toluene was used as a solvent and aqueous sodium carbonate was used as a base [22] instead of pyridine. [21] In the biphasic system the concentration of base was kept low so that the concentration of free amines was also low, leading to fewer by-products and slightly higher yields.…”

Section: Resultsmentioning

confidence: 99%

“…[21] In the biphasic system the concentration of base was kept low so that the concentration of free amines was also low, leading to fewer by-products and slightly higher yields. Use of POCl 3 [21] rather than sulfuric acid [22] in the dehydration of 3 to form 4 was found to be advantageous, since the workup was facilitated. The yield of 5 prepared from 4 d has been reported to be 98 % [23] , but we obtained only 55 ± 60 % in several attempts.…”

Section: Resultsmentioning

confidence: 99%

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Water-Binding Solid Scintillators: Synthesis, Emission Properties, and Tests in3H and14C Counting

Meyer

Wolff

2000

Chem. Eur. J.

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Spectral and time-resolved fluorescence properties as well as relative fluorescence quantum yields of carbodiimide derivatives of 2.5-diphenyloxazole (PPO) (prepared by H2S elimination from the corresponding thioureas), of some intermediates in the preparation, and of several other PPO derivatives were investigated in solution and in the solid state to test their suitability as solid scintillators. The carbodiimides reacted slowly with water under acidic conditions to yield ureas. These systems were compared with solid mixtures of other PPO derivatives with sodium sulfate as a drying agent, as chemically water-binding solid scintillators in 3H and 14C counting. Both the chemically and the absorptive water-binding scintillators proved capable of counting 3H and 14C decay, and open a way to the counting of aqueous samples by solid scintillators without a drying step.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Water-Binding Solid Scintillators: Synthesis, Emission Properties, and Tests in3H and14C Counting

Meyer

Wolff

2000

Chem. Eur. J.

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“…Presence of two bulky heterocyclic substituents in 1,2-positions of the ortho-POPOP central benzene ring results in a significant sterical hindrance. This hindrance is manifested by a prominent non-planarity of ortho-POPOPs both in the crystalline state (Doroshenko, 1994) and in solutions (Doroshenko, 1996(Doroshenko, , 2002a. All the already examined crystal structures of the ortho-analogs of POPOP are characterized by essentially different angles between the planes of the central phenylene and each of the attached heterocyclic rings.…”

Section: Methodsmentioning

confidence: 99%

“…For background to the practical applications of 1,2-bis-(5phenyl-oxazol-2-yl)benzene (ortho-POPOP) analogs (spectroscopic and fluorescence kinetics data), see: Doroshenko et al (1996Doroshenko et al ( , 1999Doroshenko et al ( , 2000aDoroshenko et al ( ,c, 2002a, Kirichenko et al (1998). For related structures, see: Doroshenko et al (1994Doroshenko et al ( , 1997Doroshenko et al ( , 2000bDoroshenko et al ( , 2002b. Table 1 Hydrogen-bond geometry (Å , ).…”

Section: Related Literaturementioning

confidence: 99%

5-(4-Fluorophenyl)-2-[2-(5-phenyl-1,3-oxazol-2-yl)phenyl]-1,3-oxazole

et al. 2010

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In the title compound, C24H15FN2O2, the dihedral angles between the central benzene ring and the oxazole rings are 10.7 (6) and 64.1 (5)°. The dihedral angles between the oxazole rings and their pendant rings are 2.0 (3) and 24.3 (2)°. The F atoms are disordered over two sites with occupancies of 0.627 (3) and 0.373 (3) in the phenylene–oxazolyl–phenyl and in oxazolyl–phenyl fragments, respectively. In the crystal structure, molecules are linked through a network of C—H⋯F and weak π–π stacking interactions.

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Molecular structural features of unsymmetrical ortho analogs of POPOP

Дорошенко¹,

Баумер²,

Kirichenko³

et al. 1997

Chem Heterocycl Compd

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and its acid chloride used in the synthesis of the ortho POPOP analogs. In the series of unsymmetrical ortho POPOP analogs there arises a unique possibility for changes in the structure of the oxadiazole part of the molecule to affect the position of the spectral emission almost without affecting the long wavelength absorption band in the process. There were thus prepared efficient organic luminophores having an anomalously large Stokes fluorescence shift.One of the problems in the physical chemistry of organic luminophores is the preparation of efficiently fluorescing compounds characterized by minimal overlap of absorption and emission spectra and, thus, an increased value of the Stokes fluorescence shift [1]. Its resolution must overcome a number of technical problems concerned with the decreased light output resulting from reabsorption of the emitted light and also the possible absorption by impurities or the products of photodecomposition arising from the use of organic luminophores (e.g., serving as active dye laser agents, in plastic and liquid scintillators, and as tracers and probes in medico-biological research).From our viewpoint, a promising means of obtaining luminescence with an anomalously large Stokes shift is the,.use of rapid processes of structural relaxation in the excited state, characteristic for sterically hindered aromatic compounds. Among these we have investigated in this report the ortho analogs of POPOP (1,4-bis(5-phenyloxazol-2-yl)benzene).In previous work we used x-ray structural analysis to investigate the structure of a series of ortho POPOP analogs in the crystalline state [2]. It was found that these compounds exist in a nonplanar and unsymmetrical conformation characterized by different angles between the planes of the central phenylene and the arylazole fragments in the 1,2 position. Vibrational methods (IR, Raman) [3] and ultraviolet spectroscopy together with quantum chemical calculations [4] have shown that the conformation characterizing the crystalline state is also retained in the solution state. We have also studied the spectroluminescence properties and the dynamics of the process of structural relaxation (flattening) of the ortho POPOP analogs in the excited state.

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Structure of sterically hindered aryl derivatives of five-membered nitrogen containing heterocyclicortho-analogs of POPOP

Cited by 15 publications

References 5 publications

Water-Binding Solid Scintillators: Synthesis, Emission Properties, and Tests in3H and14C Counting

Water-Binding Solid Scintillators: Synthesis, Emission Properties, and Tests in3H and14C Counting

5-(4-Fluorophenyl)-2-[2-(5-phenyl-1,3-oxazol-2-yl)phenyl]-1,3-oxazole

Molecular structural features of unsymmetrical ortho analogs of POPOP

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