具有膦配体的异核d10-d8配合物结构: Au-Pt配合物激发态性质的理论研究

采用MP2和DFT方法优化一系列d10-d8配合物, MM’(CN)2(PH2CH2PH2)2]＋M＝AuI, M′＝PtII (1), PdII (2), NiII (3); M’＝PtII, M＝AgI (4), CuI (5)]的基态结构, 其中BH&;H方法得到的金属间距离最接近相应的实验值. 对于经典Au-Pt配合物: 使用多种方法优化AuPt(CN)2(PMe2CH2PMe2)2]＋(1Me)的结构以验证取代基近似的合理性, 采用单激发组态相互作用方法优化了1的两个低能三重激发态并且考查了环境效应(抗衡离子和溶剂分子)对其较低能激发态发射光谱的影响. 计算结果显示1的两个低能三重激发态分别产生399和234 nm发射, 属于金属中心(Metal-centered, MC)跃迁和分子内电荷转移(Intramolecular Charge Transfer, ICT)的混合性质; 由于电子激发到成键轨道, 使得激发态金属间距离相对基态变短; 环境效应使得较低能的MC/ICT激发态的发射光谱红移, 如1•ClO的发射在473 nm处, 与实验测得AuPt(CN)2(PCy2CH2PCy2)2]•ClO4的451 nm固体发射相对应.

Theoretical Studies on Heterobimetallic d10-d8 Complexes with Phosphine Ligands: Excited-state Properties of the Au-Pt Analogue

The ground-state structures of heterobimetallic d10-d8 complexes, MM’(CN)2(PH2CH2PH2)2]＋M＝AuI, M’＝PtII (1), PdII (2), NiII (3); M’＝PtII, M＝AgI (4), CuI (5)], were optimized using density functional theory (DFT) and ab initio (MP2) methods. It was shown that the M—M’ distances calculated with the BH&;H functional are closest to the corresponding experimental values. The attempts of methods and substituent effects on the Au-Pt complex confirm the present calculations reasonable. The CIS calculations reveal that 1 features two excited states with the combined characters of MC (metal-centered) transition and ICT (intramolecular charge transfer). They give rise to the phosphorescent emissions at 399 and 234 nm, respectively, along with the promotion of electrons into bonding orbitals that results in the decrease of the Au-Pt distances in going from the ground state to the excited states. Optimizations on the lower-energy MC/ICT excited states of AuIPtII(CN)2(PH2CH2PH2)2]＋•X (1•X) (X＝Cl, Br, I, ClO, HCN and MeCN) indicated that the environment effect (counterion and solvent) results in a red shift of emission wavelength. Among these, the emission of 1•ClO was predicted at 473 nm, agreeing with 451 nm of AuPt(CN)2- (PCy2CH2PCy2)2]•ClO4 in the solid state in the experiment.