title: Rotational energy barrier of 2-(2',6'-dihydroxyphenyl)benzoxazole: a case study by NMR.
abstract: 2-(2'-Hydroxyphenyl)benzoxazole (HBO) derivatives represent an important class of luminescent materials, as they can undergo excited state intramolecular proton transfer (ESIPT). The material's ESIPT properties are dependent on the ratio of two different rotamers, whose interconversion is poorly understood. By using HBO derivative 4, the rotational energy barrier of 2- (2',6'-hydroxyphenyl)benzoxazole is determined to be 10.5 kcal/mol by variable-temperature NMR. Although a HBO derivative typically exhibits two rotamers with O···H-O (e.g., 1a) and N···H-O bonding (e.g., 1b), correlation of NMR with fluorescence data reveals that the rotamer with N···H-O bonding is predominant in the solution.
authors: Department of Chemistry & Maurice Morton Institute of Polymer Science, The University of Akron, Akron, Ohio 44325, United States.
authors: Weihua
authors: W
authors: Chen
authors: Eric B
authors: EB
authors: Twum
authors: Linlin
authors: L
authors: Li
authors: Brian D
authors: BD
authors: Wright
authors: Peter L
authors: PL
authors: Rinaldi
authors: Yi
authors: Y
authors: Pang