Synthesis And Luminescence Study Of Platinum(Ⅱ) Complexes With New Phosphine Oxide Derivatives As Ligands

With the bulky phosphine oxide derivatives as the new ancillary ligands,Pt(Ⅱ)complexes and heteronuclear Pt(Ⅱ)complexes have been synthesized.Their structures were characterized by elemental analysis,NMR and X-ray single-crystal diffraction.Their photophysical properties were systematically investigated.The HOMO and LUMO orbitals were obtained from UV-vis absorption spectra and cyclic voltammetry.1、Six novel phosphine oxide derivatives(L1-L6)based on benzimidazole,triazole and tetrazole have been synthesized.The phosphine oxide derivatives based on benzimidazole(L1,L3,L4)show very high quantum yield(Φ)of above 55% at room temperature,of which L1 is especially high(Φ=45.6% in CH2Cl2 solution,Φ=69.4% in solid state),indicating that these novel compounds are good luminescent materials.The introduction of electron-donation substituents on benzimidazole leads to the higher the luminescence quantum yield(Φ)of the compound,and the electron-withdrawing substituents results in blue shift of the emission peak.2、With phosphine oxide derivatives(L1-L5)as new ancillary ligands,five new ppy-type phosphorescent complexes(Pt-L1~Pt-L5)have been synthesized.X-ray crystallographic studies reveal that the platinum(Ⅱ)(Pt-L1~Pt-L4)binds to Lx through a N^O-coordinating mode and froms a square-planar coordination geometry.The closest Pt-Pt distance is 5.839 ?,indicating the absence of metal-metal interactions and pai-pai stacking interactions.A dinuclear complex Pt-L5 was obtainedby using triazole phosphine oxide(L5)as the ancillary ligand.Notably,complex(Pt-L5)exhibit excellent green phosphorescent emission in powder with highly quantum efficiency of 77%.The nature of the substituents in the benzimidazole group have no apparent influence on the emission spectra and HOMO and LUMO energy levels of these complexes.3 、 With the tetrazole phosphine oxide(L6)as the ancillary ligand,six heteronuclear complexes(Pt-L6-M,M= Na、Fe、Zn、Mg、Ca、Cd)have been synthesized.The molecular structure of the complex Pt-L6-Na is quite unique,in which the Pt(Ⅱ)centre is six coordinated forming a distorted octahedral geometry.theThe O atoms of-P=O groups are not involved in the coordination with Pt(Ⅱ)in this series of complexes.These heteronuclear complexes(Pt-L6-M)in powder exhibit excellent luminescent efficiencies at room temperature(Na: 62.5%,Fe: 54.2%,Zn: 54.6%,Mg: 58.9%,Ca: 42.8%,Cd: 41.6%).However,the quantum efficiencies of these complexes Pt-L6-M(M= Na、Fe、Zn、Mg、Ca、Cd)in solution are especially high with values of 55.4%,94.1%,93.7%,94.2%,89.0%,88.6%.respectively.The emission spectra of these complexes at 77 K confirm that the phosphorescent emissions of all the Pt(Ⅱ)complexes are indeed 3LC in nature.