Comparative study on bulk and composite fibrous samples photophysical feature: synthesis and characterization of a fluorine-containing Re(I) complex and its electrospinning fibers.

This paper reported a diamine ligand 2-(4-fluorophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (referred to as FPOZ) owing two typical electron-withdrawing moieties of an oxidiazole group and a fluorine atom, as well as its corresponding Re(I) complex Re(CO)3(FPOZ)Br. Geometric structure and electronic nature of Re(CO)3(FPOZ)Br were explored and discussed by single crystal analysis and theoretical calculation, which suggested that Re(CO)3(FPOZ)Br took a distorted octahedral coordination field. The onset electronic transitions owned a mixed character of metal-to-ligand-charge-transfer (MLCT) and ligand-to-ligand-charge-transfer (LLCT). Re(CO)3(FPOZ)Br was then doped into a polymer host. Photophysical difference between resulting composite fibers and bulk Re(CO)3(FPOZ)Br was carefully performed, so that the correlation between emissive performance and electron-withdrawing group/geometric relaxation could be investigated. It was found that the immobilization in polymer matrix could repress MLCT excited state geometric relaxation, leading to improved PL parameters such as emission blue shift, longer excited state lifetime and higher photostability.