Theoretical Investigation On The Luminescent Properties Of Cu(Ⅰ) Complexes

Transition metal complexes, such as iridium(Ir), platinum(Pt), osmium(Os), gold(Au) and other complexes, have received a great deal of attention due to the high luminous efficiency, brightness, resolution, wide viewing angle and fast response speed, and many other advantages. Their prohibitive cost and less abundant in the earth’s crust hampered the widely application. Cu(I) complexes due to the low cost, environment-benignancy, the lack of non-emissive low-lying MC levels, and various coordination geometries have emerged as particularly promising candidate materials.In this paper, we systematically studied the Cu(I) complexes with quantum-chemical methods and obtained the structures of the ground state and the lowest triplet excited state, energy gaps, absorption, emission spectra and other photophysical properties. The aim of the present work is to provide an indepth understanding of the effect of structure-property relations and offer some guidance for the design of excellent phosphorescent Cu(I) complexes.The main contents are listed as follows:1. Based on the experimental complexes, we analyze the structural and photophysical properties diference between the cationic and neutral Cu(I) complexes. The results show that the loss of a proton and the counterion have an important impact on the energy levels and electron density distribution of the frontier molecular orbitals. The neutral complexes are more likely to have a positive influence on the charge transfer and the transport equilibrium property than the ionic complexes by lacking of the mobile counterion. The neutral complexes have higher photoluminescence quantum yield(PLQY). Furthermore, the results show that introducing the ether linkage together with lacking of a proton and the counterion in complexes will more efficiently increase the PLQY.2. Based on the experimental complexes, we are interested in further exploring the effect of the nitrogen atom number in the five-membered nitrogen heterocycles on the photophysical properties of these Cu(I) complexes. It is found that the emission wavelength blue-shift and PLQY gradually increase when the number of nitrogen atoms is less than three. Furthermore, the PLQY of the complex 4 which has four nitrogen atoms in the five-membered nitrogen heterocycles is lower than the complex 3, but larger than the complex 2. The calculated results show that the PLQY show an apparent dependence on the the nitrogen atom number in the five-membered nitrogen heterocycles, and the increasing number of nitrogen atom is not necessary for increasing PLQY. The complex 3 with 1,2,4-triazole-pyridine-based N^N ligands are believed to be potential emitters with high phosphorescence efficiency.