On the synthesis and characterization of Ru(II)-doped polymer fibers: Polymer immobilization effect on Ru(II) emitter photophysical performance and singlet oxygen generation

Abstract

Low dimensional nanostructures has been considered as a research hotspot. Electrospinning is a classic method for synthesizing one-dimensional nanostructures. In this paper, a representative electro-acceptor group (trifluoromethyl phenyl) and a representative electron-donor group (thiophen-2-yl) were cooperated into a diamine ligand. Corresponding Ru(II) complexes were synthesized as well, so that the correlation between emission performance of these Ru(II) complexes and ligand structure could be tentatively discussed. Their geometric structure and electronic structure were discussed by their single crystals and density functional theory calculation. These Ru(II) complexes were doped into a polystyrene (PS) matrix via electrospinning method. A full comparison between pure Ru(II) complexes and their composite nanofibers was performed, including emission wavelength, emission quantum yield, emission lifetime and stability. The 1O2 generation performance was tentatively discussed as well. The PS polymer immobilization effect on these Ru(II) complexes was confirmed, including emission blue shift, improved emission quantum yield, longer emission lifetime and better photostability. An improved 1O2 generation performance was observed as well. On the other hand, the polymer immobilization effect on photophysical performance in these Ru(II) complexes, especially emission blue shift, was not as obvious as that in Cu(I) complexes. This was attributed to the heavy participation of metal d orbital in frontier molecular orbitals. An electron-accepting group (trifluoromethyl phenyl) decreased the metal contribution, resulting in a wider energy gap between HOMO and LUMO, and a more obvious polymer immobilization effect.