Improved photophysical property from electrospinning composite fibers doped with Re(I) complex: Construction, characterization and photophysical features

In this paper, a diamine ligand 2-(4-chlorophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (denoted as PPYO) and its corresponding Re(I) complex Re(CO)3(PPYO)Br which had a large conjugation plane and an electron-accepting group in its molecular structure were synthesized. Single crystal analysis revealed its successful synthesis, as well as its geometric structure. Density functional theory calculation on Re(CO)3(PPYO)Br suggested that the onset of electronic transitions owned mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer, which suffered badly from structural relaxation. Then, Re(CO)3(PPYO)Br was doped into a polymer host by electrospinning method to repress the structural relaxation, hoping to achieve improved emissive performance. Photophysical comparison between bulk Re(CO)3(PPYO)Br and composite fibers was carried out. It was found that polymer matrix immobilization could effectively repress the structural relaxation, showing improved emissive parameters, including emission blue shift, increased excited state lifetime, narrowed emission spectrum and good photostability.