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

Structure-Property Relationships in Mixed Oligoheterocycles Based on End-Capped Oligothiophenes

“…This agrees with a previous optical study on heteroanalogs of the wellknown laser dye 1,4-bis(5-phenyl-2-oxazolyl)benzene with combinations of p-phenylene, furan, oxazole, 1,3,4-oxadiazole, and thiophene units: A decrease in fluorescence intensity was found especially in the systems in which a thiophene unit was incorporated into the center of a pentameric system. [15] Theoretical calculations showed that 80% of the S 0 ǞS 1 * transition is located on the three central rings, and, accordingly, the presence of a thiophene ring in the central position causes a decrease in fluorescence quantum yield as a consequence of the heavy-atom effect. [29] These findings confirm the distinctly higher fluorescence quantum efficiency of oxadiazole pentamer 11 compared to that of the corresponding oligomer 4.…”

“…More electron-deficient systems, represented by trimeric to pentameric combinations of thiophene/thiazole, [12] thiophene/1,3,4-thiadiazole, [13] and thiophene/ 1,3,4-oxadiazole [14] [15] were synthesized as optical brighteners, (laser) dyes, UV protectors, and as model compounds for corresponding polymers. The hypervalent nature of sulfur was taken advantage of, and thiophene and thiophene 1,1-dioxide units were combined to synthesize a series of electron-deficient oligothiophene S,S-dioxides.…”