A Theoretical Investigation Into The Homo-and Heteroleptic Cu(Ⅰ) Phosphorescent Complexes

The transition metal complex as organic electrophosphorescent material can use triplet and singlet excitons at the same time,which greatly improves the luminous efficiency.Especially the rare precious metals iridium,platinum,osmium and other organic metal complexes have excellent performance,but their application is limited due to their disadvantages such as not environmentally friendly and high price,so it is urgent to develop new alternative materials.Cu(Ⅰ)complexes are ideal candidates for metal complex luminescent materials due to their low price,environmental friendliness,and lack of low-energy metal center(MC)d-d * transitions.In this paper,DFT / TDDFT methods are used to study the ground and excited state structures of a series of Cu(Ⅰ)complexes,the radiative transition rate,and the factors affecting the non-radiative transition rate,through the study of this series of complexes,the effects of the ligands from N^N to P^P in Cu(Ⅰ)complexes on the electronic structure and light-emitting properties are explained.The studies of the radiative transition process have shown : Molecule 1 has the highest MLCT ratio,which results in a larger orbital coupling effect than other molecules,which in turn leads to the highest radiation transition rate;Molecule 2 also has the highest triplet excitation energy and a high degree of coordination between the oscillator strength and the spin-orbit coupling matrix element,so it has a larger radiative transition rate;Molecule 4,its single-electron single-center rotation-orbit integral is zero,the radiation transition rate is zero.That means the acceptor type ligand(N^N)makes the metal participate in transition(MLCT)with a higher proportion;and the donor type ligand(P^P)makes the ratio of ligand to ligand transition(LLCT)high.The studies of the non-radiative transition process shown: molecule 2 effectively inhibits the bending vibration of the N^N ligand due to the steric effects between the N^N ligand and the P^P ligand,so it has a smaller recombination energy,resulting in the reduction of non-radiation rate.For the heteroleptic molecule 3,due to the addition of the2phenyl-phosphorus structure in the NP ligand,the conjugate nature of the original N^N ligand was destroyed,and there was no large steric effects ligand fills this coordination space,causing the rocking vibration of the benzene ring connected to the P atom in the NP ligand to increase,resulting in molecule 3 with the largest recombination energy and a bigger non-radiative transition rate.This paper theoretically illustrated the effect of different coordination structures on the luminescent properties of Cu(Ⅰ)complexes,explained the reason why the heteroleptic complex with both donor and acceptor ligends has better development prospects,provided a valuable reference for the structure control of Cu(Ⅰ)complex luminescent materials.