Azlactone molecules can be protonated in acidic media, and the process of protonation is irreversible due to ring opening in solutions A new fully reversible pH sensor has been developed 4-(p-N,N-dimethylamino phenyl methylene)-2-phenyl-5-oxazolone (DPO), an azlactone derivative, embedded in a plasticized PVC polymer film The sensor membrane is completely transparent and exhibits pH induced color change which is capable of measuring of pH in the range 1–7 and has a pKa value of 34 In agreement with crystal phase studies, DPO displays enhanced fluorescence emission quantum yield, Qf=052, and fluorescence emission lifetime, τ f =135 ns , in immobilized PVC film matrix, compared to Qf≅003 and τ f =002–003 ns in solutions Stokes shift decreased to 46 nm in plasticized PVC film, with respect to Stokes shift of 81 nm in acetonitrile solution Singlet energy, E s =604 kcal mol −1 , of DPO in PVC film, which is 11–14 kcal mol−1 lower with respect to solutions, is taken as evidence of lessened singlet–triplet crossings in excited state of DPO in immobilized phase, and result in enhanced fluorescence emissions

Fluorescence emission studies of an azlactone derivative embedded in polymer films: An optical sensor for pH measurements

Absorption and fluorescence wavelengths for a series of a lactones have been measured from acetonitrile solutions that had no pre-light exposure. Fluorescence quantum yields, Qp are found to be in general less than 0.01, excluding the the derivatives with naphthyl and p-dimethylaminophenyl substituents. Previously reported Q F values did not not fit to our results. # On leave of absence from Department of Chemistry, Faculty of Science, Ege University, Izmir (Turkey). ∗∗ Permanent Address: Department of Chemistry, Faculty of Science, Eastern Mediterranean University, Gazi Magosa, North Cyprus, Mersin 10 (Turkey).

NMR, Absorption and Fluorescence Parameters of Azlactones

Experimental and theoretical evaluations have proven that very low fluorescence quantum yields of azlactones in solution are not caused by an efficient inter system crossing from S1*(ππ) to T*(nπ) states, but rather from solvation and steric effects, that result in non-planarity of the molecular system. High fluorescence quantum yields in the solid state are attributed to the planarity of the azlactone molecule upon packing into the crystal lattice. Supporting evidence was found upon observation of the excited state proton transfer (ESIPT) bands of fluorescence emissions of o-hydroxyarylidene derivatives. The photoinstability of azlactones in liquid states are attributed to photochemical E-Z isomerization and cleavage of the hetero ring α to the carbonyl group.

Structure and Luminescent Properties of the 4-Arylidene-2-Aryl-5-Oxazolones(Azlactones)In Solution and Crystalline State

Synthesis of symmetrical 2,2′,4,4′‐tetrasubstituted[4,4′‐bioxazole]‐5,5′(4H,4′H)‐diones and their reactions with some nucleophiles

The reaction of tetracyclone (1) with potassium in THF gave a mixture of benzoic acid (4), tetraphenylfuran (5) and cis-1,2-dibenzoylstilbene (6). The reaction of 1 with potassium in oxygen-saturated THF gave a mixture of 2-hydroxy-2,4,5-triphenyl-3(2H)furanone (3), 4, 5 and 6, whereas the reaction of 1 with potassium superoxide gave a moderate yield of 3,4,5,6-tetraphenyl-2-pyrartone (7), besides 3, 4, 5, and 6. The reaction of tetraphenylfuran (5) itself with potassium in THF gave a mixture of 6, 1,2,3,4-tetraphenylbutan-1-one (9), 2,3-diphenyl-1-indenone (10) and 2,3-epoxy-4-hydroxy-2,3,4-tnphenyltetralone-l (11), whereas practically no reaction occurred on treatment of 5 with potassium superoxide. Treatment of 10 with potassium in THF, however, gave a mixture of 4, dibenzo[a,c]-13-fluorenone (13), 2,3-diphenyl-2-hydroxyl-1-indanone (14) and 2,3-diphenylbenzofuran (15). A similar mixture of products consisting of 4, 13, 14 and 15 was obtained when the reaction of 10 with potassium was carried out in oxygen-saturated THF or when 10 was treated with potassium superoxide. Treatment of 2,3-diphenyl-2,3-epoxy-1-indanone (16) with potassium on the other hand, gave 10 in excellent yield. Cyclic voltammetric studies have been carried out to measure the reduction potentials of 1, 5, 10 and 16 in the generation of their radical anions. The radical anions of 1, 5, 10 and 16 were also generated pulse radiolytically in methanol and their spectra showed absorption maxima in the region 320–380 nm.

Electron transfer reactions. Reaction of tetracyclone, tetraphenylfuran and related substrates with potassium

The reaction of several Δ2-oxazolin-5-ones (1a–c, 12) and bioxazolinones (17, 26) with potassium in THF has been investigated. Treatment of 1a with potassium in THF gave a mixture of dibenzamide (1...

/pdf/electron-transfer-reactions-reaction-of-d2-oxazoline-5-ones-13ckfw6v1s.pdf

Electron transfer reactions. Reaction of Δ2-oxazoline-5-ones and related substrates with potassium

On propose des mecanismes mettant en jeu la formation initiale d'intermediaires sous forme de radicaux anions

R. K. Tikare

Papers

Electron transfer reactions. Reaction of Δ2-oxazoline-5-ones and related substrates with potassium

Electron transfer reactions. Reaction of nitrones with potassium1

Electron Transfer Reactions. Reaction of Sydnones with Potassium.