Studies On The Design Of D⁸/d¹⁰ Heteronuclear Metal Alkynyl Complexes And Their Electroluminescence

Organic light-emitting diodes(OLEDs)display huge application potential in flat panel display and solid-state lighting.One of the most key components in OLEDs is emitting material.Since strong spin-orbital coupling affords large singlet-triplet energy gap in phosphorescent heavy metal complexes,both singlet and triplet excitons can be fully utilized to emit electroluminescence.Over these years,various phosphorescent heavy metal complexes with iridium(?),platinum(?),Os(?),Au(?)and copper(?)etc have been intensely investigated as emitting materials in OLEDs.Compared with most of mononuclear cyclometallated iridium(?)and platinum(?)complexes used in OLEDs,many polynuclear metal cluster complexes are more readily available in mild conditions and exhibit higher thermal and photochemical stability due to additional metal-metal interaction with the energy comparable to hydrogen bond(25-40 kJ mol-1).Nevertheless,phosphorescent metal cluster complexes have been much less investigated as emitting materials in OLEDs.In this thesis,designed synthesis of five triphosphine-supported PtAg2 and PtAu2 heterotrinuclear complexes with phenothiazine or carbazole functionalized acetylides were carried out.These phosphorescent heterotrinuclear cluster complexes were used as light-emitting materials in OLEDs to achieve high-efficiency green,yellow and orange electroluminescence through solution process.This thesis includes two sections.(1)Three highly phosphorescent cationic PtAg2 heterotrinuclear complexes with different positioned 9-ethylcarbazole-acetylide ligands were prepared.As demonstrated by X-ray crystallography,the PtAg2 structure supported by dual bis(2-diphenylphosphinomethyl)-phenylphosphine(dpmp)is highly stabilized by the formation of four five-membered coordination rings as well as significant Pt-Ag interaction.The doped films with host materials exhibit intense phosphorescent emission at 527,547 and 509 nm with quantum yields of 64.4%,45.5%and 38.9%for compounds 1-3,respectively.Taking advantage of doped films with blended host as light-emiting layers,solution-processed OLEDs gave maximum current and external quantum efficiencies of 67.4 cd/A and 17.4%,58.4 cd/A and 15.3%,and 25.2 cd/A and 6.8%for PtAg2 complexes with 9-ethylcarbazole-2-acetylide,9-ethylcarbazole-3-acetylide and 9-ethylcarbazole-4-acetylide to afford green,yellow-green and green electrophosphorescence,respectively.(2)Triphosphine-participated PtAu2 heterotrinuclear complexes with phenothiazine-functionalized acetylides were prepared.The crystal structural dermination indicates that PtAu2 heterotrinuclear array is supported by double triphosphine ligands with substantial Pt-Au intermetallic contact in view of a short Pt-Au distance of 2.95 ?.The PtAu2 complexes shows moderate phosphorescent emission in fluid solution and powder state as well,but intense phosphorescence in doped PMMA films with quantum yields of 73.7%and 48.9%for orange and yellow emitting complexes,respectively.Utilizing blended host materials composed of both hole-transport TAPC/TCTA and electron-transport OXD-7 doping with 8%phosphorescent PtAu2 complex as emitting layer,solution-processed OLEDs gave orange electroluminescence with the highest current efficiency of 35.4 cd/A and external quantum efficiency of 18.7%.