A Tris-Cyclometalated Iridium(III)Complex of 2-(5,5-Dioxido-dibenzothiophen-3-yl)pyridine:Synthesis,Structural,Redox and Photophysical Properties

摘要

The first cyclometalated dibenzothiophene S,S-dioxide derivative,namely[fac-2-(5,5-dioxidodibenzothiophen-3-yl)-pyridine]iridium(III)(3)has been synthesised in high yield and characterised by X-ray crystallography,solution electrochemistry,absorption and emission spectroscopy.The Ir atom has a fac-octahedral coordination with three chelating li-gands(A,B and C);each Ir-N bond is in trans position to an Ir-C bond.In cyclic voltammetry experiments in dichloro-methane,complex 3 undergoes a reversible metal-centred Ir~(III)/Ir~(IV)oxidation at E_(1/2)~(ox)=+1.04 V vs.Ag/Ag~+reference electrode.Complex 3 exhibits bright green photolumines-cence(lambda_(amx)=525 nm in toluene)from mixed 3MLCT/3 pi->pi* states with quantum yield(PHI_(PL))of 0.26 in toluene solution.The phosphorescence emission decay follows first order kinetics,with a lifetime of 4.9 mu s.A comparison of complex 3 with analogues 1 and 2,where the dibenzothiophene S,S-dioxide unit is replaced by 9,9-dihexylfluorene and N-hexyl-carbazole respectively,establish that the substituent para to the Ir metal atom,i.e.CR2 in 1,NR in 2 and SO2 in 3,has a major influence on the redox and emission properties in this series.Organic light-emitting diodes(OLEDs)were fabricated by spin-coating techniques using a polyspirobifluorene copolymer(PSBF)as a host and complex 3 as dopant.In a single-layer blend configuration ITO/PEDOT:PSS/PSBF:3(8 wt.-%)/Ba/Al OLEDs showed pale blue/white light emission(CIE coordinates:x=0.29,y=0.31)arising from a combination of fluorescence from the host copolymer(lambda_(max)=450 nm)and phosphorescence from 3(lambda_(max)=530 nm).