Deliberate control of intermolecular interactions in fluorene- and benzofluorene-cored oligomers was attempted via introduction of different-length alkyl moieties to attain high emission amplification and low amplified spontaneous emission (ASE) threshold at high oligomer concentrations. Containing fluorenyl peripheral groups decorated with different-length alkyl moieties, the oligomers were found to express weak concentration quenching of emission, yet excellent carrier drift mobilities (close to 10−2 cm2/V/s) in the amorphous films. Owing to the larger radiative decay rates (>1.0 × 109 s−1) and smaller concentration quenching, fluorene-cored oligomers exhibited down to one order of magnitude lower ASE thresholds at higher concentrations as compared to those of benzofluorene counterparts. The lowest threshold (300 W/cm2) obtained for the fluorene-cored oligomers at the concentration of 50 wt % in polymer matrix is among the lowest reported for solution-processed amorphous films in ambient conditions, what makes the oligomers promising for lasing application. Great potential in emission amplification was confirmed by high maximum net gain (77 cm−1) revealed for these compounds. Although the photostability of the oligomers was affected by photo-oxidation, it was found to be comparable to that of various organic lasing materials including some commercial laser dyes evaluated under similar excitation conditions.
Treatment of ambident sodium salt of 2-methylsulfanyl-4(3H)-quinazolinone with methyl bromoacetate resulted in N (3) -alkyl ester formation. Reaction of the resulted ester with hydrazine hydrate gave 2-methylsulfanyl-4-oxo-3(4H)-quinazolinyl)acetohydrazide, which underwent intramolecular cyclization under heating in dimethylformamide to give 1-aminoimidazo[2,1-b]quinazoline-2,5(1H,3H)-dione. The latter took place in acylation reaction and in condensation with aromatic aldehydes.
Fused pyrimidine derivatives R 0515 Synthesis and Intramolecular Cyclization of 2-Methylsulfanyl-4-oxo-3(4H)-quinazolinyl Acetohydrazide. -Products (IV), (IX) and (XIa) exhibit antiinflammatory activity for 35-39%. -(BURBULIENE*, M. M.; BOBROVAS, O.; VAINILAVICIUS, P.; J.
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