Construction, characterization and photophysical study on electrospinning composite fibers doped with phosphorescent Re(I) complex

• A ligand having conjugation chain and electron-accepting group was designed.
• Its Re(I) complex was characterized by single crystal and DFT calculation.
• Its excited state suffered from bad geometric relaxation.
• This geometric relaxation was limited by doping it into a polymer matrix.
• Polymer immobilization effect on emissive performance was confirmed.

This paper reported a diamine ligand 2-(4-bromophenyl)-5-(pyridin-2-yl)-1,3,4-oxadiazole (cited as BrPO for short) having a large conjugation chain and an electron-withdrawing group. Its corresponding Re(I) complex Re(CO)3(BrPO)Br was full characterized, including its single crystal structure and electronic transition nature. It was found that Re(CO)3(BrPO)Br took a distorted octahedral coordination mode. Its photo-induced transitions all showed a mixed character of metal-to-ligand-charge-transfer and ligand-to-ligand-charge-transfer. Experimental data suggested that Re(CO)3(BrPO)Br excited state suffered from bad geometric relaxation. To improve emission performance, Re(CO)3(BrPO)Br was doped into a polymer host using electrospinning method so that this geometric relaxation could be limited. The photophysical comparison between pure sample and composite sample was performed. Results suggested that the immobilization in polymer matrix could effectively suppress such geometric relaxation, giving improved emission performance such as emission blue shift, narrowed emission band, longer excited state lifetime and improved photostability.

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