Design,Synthesis and Properties of Cu(Ⅰ)Complexes with a Nitrogen-containing Spirocycle Ligand for Delayed Fluorescence Materials
In this study,a Cu(Ⅰ)complex luminescent material Cu-P-Spiro2N with thermally activated delayed fluorescence(TADF)properties was successfully designed by combining the donor-acceptor(D-A)type ligand 10-phenyl-10H-spiro[acridine-9,9'-(4,5-diazafluorene)](Spiro2N)with long afterglow emission properties and the auxiliary phosphine ligand bis(2-diphenylphosphinophenyl)ether(POP).The molecular structures of the Cu(Ⅰ)complex were con-firmed by nuclear magnetic resonance spectroscopy,and the crystal structure of the Cu-P-Spiro2N complex was further char-acterized by X-ray single crystal diffraction.Cu-P-Spiro2N belongs to the triclinic crystal system with cell parameters a=90.14(2)°,β=115.43(3)°,y=115.55(3)°,a=15.10(6)nm,b=15.15(4)nm,c=16.62(6)nm.Due to the two mutually or-thogonal π-conjugated planar structures of the ligand molecule Spiro2N,its highest occupied molecular orbital(HOMO)and lowest unoccupied molecular orbital(LUMO)are well separated,but with a relatively large singlet-triplet energy gap(△EsT).After coordination of the metal Cu(Ⅰ)fragment with the ligand Spiro2N,the energy gap between HOMO and LUMO is fur-ther reduced,and the charge transfer(CT)state energy level is further lowered,which makes the complex Cu-P-Spiro2N have a very small △EsT of 0.05 eV.The small △EsT facilitates the reverse intersystem crossing process,thereby achieving TADF emission.The emission of this complex mainly comes from the D-A ligand Spiro2N,which exhibits metal perturbation in-tramolecular ligand charge transfer(ILCT)properties.At room temperature,in the doped polymethylmethacrylate(PMMA)film(10％(w)),the Cu-P-Spiro2N complex exhibits strong yellow light emission with an emission peak at 551 nm,a photo-luminescence quantum efficiency of 49％,and an excited state lifetime of 6.3 μs.The results of this study indicate that by coordinating with Cu(Ⅰ)ions,the excited state energy level of the ligand molecule can be modulated,reducing △EST and thus achieving TADF emission.
Cu(Ⅰ)complexthermally activated delayed fluorescencedonor-acceptor type ligandenergy level tuning
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