Effects of the π-conjugation length of bipyridyl ligand on the photophysical properties of binuclear organotin(IV) complexes: Synthesis and characterization of dimethyltin(IV) complexes with bipyridyl

•Two organotin(IV) complexes were prepared and used for fabrication of OLEDs devices.•Effect of ligands on electroluminescence properties of the OLED was investigated.•Correlation exists between the π-conjugation length and emission wavelength.

The dimethyltin(IV) complexes of rigid bipyridyl-based ligands, 4,4′-bipyridine (4,4′-bipy) and 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene (4-bpdb), were prepared and characterized by 1H, 13C and 119Sn NMR, IR, and UV spectroscopies, single-crystal X-ray diffraction and elemental analysis. The prepared complexes were used as green and yellow-orange electroluminescence dopant materials to fabricate organic light-emitting diodes (OLEDs) with a general configuration of ITO/PEDOT:PSS(90 nm)/PVK:PBD:tin-complexes (80 nm)/Al(200 nm). The effects of long and rigid bipyridyl-based ligands on the electroluminescence properties of the complexes were investigated. The maximum emission peaks showed that a good correlation exists between the π-conjugation length of bipyridyl ligands and emission wavelength. Replacing 4-bpdb with the long π-conjugation length, 4,4′-bipy, resulted in red shifts in both absorption and fluorescence spectra and moderately enhanced the photoluminescence intensity and the fluorescence quantum yield. Furthermore, complex of dimethyltin(IV) with 4-bpdb ligand was doped into a PVK:PBD blend as the host in two different concentrations. It was found that the high concentration of dopant caused a trap effect in the current voltage and led to a self-quenching of emission and reduced the efficiency of the device.

Graphical abstractTwo binuclear organotin(IV) complexes were prepared and characterized by 1H, 13C and 119Sn NMR, IR, and UV spectroscopes and single-crystal X-ray diffraction. The prepared complexes were used as green and yellow-orange EL dopant materials to fabricate organic light-emitting diodes (OLEDs).Figure optionsDownload full-size imageDownload as PowerPoint slide