Synthesis And Properties Of Some Novel Iridium(?)Complexes

In recent years,organic light-emitting devices(OLEDs)have caught more and more attention due to its superiority of self-illumination,high-resolution image,extremely light and thin screen,flexible display and so on.Now OLEDs have been commercialized in smart television,smartphone,smartwatch and solid state lighting.Among various emitting materials used in OLEDs,phosphors have shown great advantages because their theoretical internal quantum efficiency can reach 100%.And compared with many other phosphorescent metal complexes,iridium(?)complexes are particularly outstanding due to their easily modified chemical structures,facile control of photophysical properties,short triplet lifetime and excellent thermal stabilities etc.In this thesis,we designed a series of novel phosphorescent Ir(?)complexes by changing cyclometalated ligands or ancillary ligands with different structures.Crystal structures,thermal stabilities,electrochemical properties,photophysical properties and theoretical calculations of these complexes were analyzed.What's more,devices based on these complexes were fabricated and their performances were further studied.Two main aspects of this research are as follows.1.Two Ir(III)complexes Ir(tfpmd)2(stpip)and Ir(tfpqz)2(stpip)with green and red emissions were synthesized,in which 2-(4-(trifluoromethyl)phenyl)pyrimidine(tfpmd)or 4-(4-(trifluoromethyl)phenyl)quinazoline(tfpqz)was chosen as the cyclometalated ligand and bis(diphenylphorothioyl)amide was used as the ancillary ligand,respectively.The green OLED using Ir(tfpmd)2(stpip)as emitting material displays good performances with a maximum luminance(Lmax)of 39634 cd m-2,a maximum current efficiency(?c,max)of 90.5 cd A-1 and a maximum external quantum efficiency(EQEmax)of 30.8%,respectively.The red OLED with Ir(tfpqz)2(stpip)also shows decent characteristics with a Lmax of 33732 cd m-2,a ?c,max of 28.6 cd A-1 and an EQEmax of 18.3%,respectively.The cyclometalated ligands containing nitrogen heterocycles and ancillary ligand with bulky group both help to improve electron mobility,balance transportation of carriers,broaden the recombination zone and suppress current leakage in the devices.As a result,green and red OLEDs show high efficiencies and extremely low efficiency roll-offs.This work provides an effective idea for designing efficient green and red Ir(?)complexes by introducing a bis(diphenylphorothioyl)amide ancillary ligand.2.Eight new neutral Ir(?)complexes(Irl-Ir8)bearing strong electron withdrawing pentafluorosulfanyl(-SF5)group were synthesized.2-(3/4-(Pentafluorosulfanyl)phenyl)pyrimidine(3/4-pmd),1-(3/4-(pentafluorosulfanyl)phenyl)isoquinoline(3/4-piq)and 2-(3/4-(pentafluorosulfanyl)phenyl)pyridine(3/4-ppy)were designed as cyclometalated ligands and 2,2,6,6-tetramethylheptane-3,5-dione(tma),tetraphenylimidodiphosphinate(tpip)and bis(diphenylphorothioyl)amide(stpip)were chosen as ancillary ligands.These complexes display skyblue,green and red emissions,respectively.And the introduction of-SF5 on the cyclometalated phenyl ring leads to an obvious blue-shift in the emission color compared to the complexes with similar molecular structures except-SF5 unit.The devices based on Ir5/Ir6 were fabricated and from the results it can be seen that the electron-withdrawing ability of-SF5 is far too strong that the electron mobility in the device may be greatly reduced and therefore the electrons and holes cannot be combined effectively.As a result,complexes containing-SF5 are not suitable for conventional OLED devices.Furthermore,taking Ir2 as an example,we also explored its application in ion detection and the preliminary results show that Ir2 could potentially be used to detect Hg2+.