Influence of medium acidity upon the luminescence properties of 2,5-diphenyl-1,3,4-oxadiazole and 2,5-diphenyl-1,3-oxazole

Synthesis and optical and electrochemical properties of novel polyethers containing isolated distyrylbenzene derivatives and side‐aromatic 1,3,4‐oxadiazole chromophores

“…The absorptions at 250 and 304 nm are due to phenyl and oxadiazole groups, respectively. 20 The absorption maximum ( max ) of P1 locates at 387 nm, whereas those of P2-P4 locate at 380, 378, and 378 nm, respectively. These absorptions arise from the -* transition of the isolated distyrylbenzene derivatives in the main chain.…”

Protonation of Sulfonated Poly(4,4′‐diphenylether‐1,3,4‐oxadiazole) Membranes

“…The protonation led to only one form of conjugated acid, although 1,3,4-oxadiazole has two equal basic centers. [16][17][18][19] In the present work, sulfonated polyoxadiazole dense membranes were treated with sulfuric acid and the protonation conditions (concentration and time) were carefully determined. Besides that, the effect of the acid concentration on the proton conductivity are discussed.…”

“…The presence of the electronwithdrawing oxygen atom in the ring stabilizes the s lone pair of electrons at the nitrogen and this tends to reduce the proton affinity of this base. [16][17][18][19] A theoretical protonation level equal to 1 will be reached when one nitrogen atom from the oxadiazole ring of the polymer repeating unit is protonated. A schematic representation of the SPOD-DPE protonation is proposed in Scheme 2 for three conditions: a) protonation level <1, where one sulfuric acid molecule provides less than one proton for repeating unit of oxadiazole ring, b) protonation level ¼ 1, which leads to a conjugated acid form of oxadiazole ring and c) protonation level >1, which also leads to a conjugated acid form of the oxadiazole ring, and the excess of sulfuric acid favors hydrogen bonds between their molecules in addition to those between them and the sulfonic acid group of SPOD-DPE.…”

Basicity of 2-phenyl-5-R-1,3,4-oxadiazoles

“…We previously determined the basicity constants for a series of 2-aryl-5-phenyl-1,3,4-oxadiazoles, and also quantitatively established the effect of the electronic properties of the benzene ring substituents on the pK BH + of these heterocycles [3]. For 2,5-diphenyl-1,3,4-oxadiazole, we determined the basicity constants in the S 0 and S 1 states, and we also studied the effect of the acidity of the medium on its luminescent spectral properties [4].In this paper, we use the spectrophotometric method to determine the basicity constants of a series of 2-phenyl-5-R-1,3,4-oxadiazoles containing different types of substituents at the 5 position of the heterocycle (1-7), plus 2,2'-diphenyl-5,5'-di-1,3,4-oxadiazole (8). N O N R Ph 1-8 1 R = H; 2 R = Ме; 3 R = CH 2 Ph; 4 R = t-Bu; 5 R = CH 2 Cl; 6 R = CCl 3 ; 7 R = CF 3 ; 8 R = 2-phenyl-1,3,4-oxadiazol-5-yl…”

“…We previously determined the basicity constants for a series of 2-aryl-5-phenyl-1,3,4-oxadiazoles, and also quantitatively established the effect of the electronic properties of the benzene ring substituents on the pK BH + of these heterocycles [3]. For 2,5-diphenyl-1,3,4-oxadiazole, we determined the basicity constants in the S 0 and S 1 states, and we also studied the effect of the acidity of the medium on its luminescent spectral properties [4].…”