Three new heteroleptic [Cu(NN)P₂]⁺ type cuprous complexes 1–3 were designed and synthesized by utilizing a diimine ligand 5-methyl-2-(2′-pyridyl)-benzoxazole (MePBO) and different phosphine ligands PPh₃ (1), m-Tol₃P (2) and POP (3), (PPh₃=triphenylphosphine, m-Tol₃P=tris(3-methylphenyl)phosphine, POP=bis[2-(diphenylphosphino)phenyl]ether), respectively. All complexes were characterized by single-crystal X-ray diffraction, spectroscopic analysis (IR, UV-Vis), elemental analysis, and photoluminescence study. Single-crystal X-ray diffraction revealed that complexes 1–3 all adopt discrete cation complex structure with a tetrahedral CuN₂P₂ coordination geometry with diverse P−Cu−P angles. Their UV-Vis absorption spectra exhibit a blue-shift sequence under the enlarging of P−Cu−P angle from 3 to 2 then to 1. The PL emission peak wavelengths of 1–3 also present similar blue-shift sequence (3→1/2). Their microsecond PL lifetime indicates that their PL behavior belongs to phosphorescence. TD-DFT calculation and wavefunction analysis illuminate that the S₁ and T₁ states of 1–3 should all be assigned as (ML+L′L)CT states. Their UV-Vis absorption and phosphorescence should be attributed to the charge transfer from the P−Cu−P segment to the MePBO ligand. Therefore, as P−Cu−P angle increases (lower HOMO), the energy of S₁ and T₁ states also increase, following the change of PL color. Additionally, the steric hindrance from substituents of phosphine ligand, as well as extra strong intra-molecular π−π stacking interactions should effectively inhibit nonradiative decay so that an abnormal PL emission blue-shift is observed from 1 to 2.

中文翻译：

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二亚胺 MePBO 配体的杂配亚铜配合物及其对磷光颜色的结构影响：合成、结构表征、性质和 TD-DFT 计算

三个新的杂[铜（NN）p ₂ ] ⁺型亚铜络合物1 - 3被设计，并且通过利用一个二亚胺配体的合成5-甲基-2-（2'-吡啶基） -苯并唑（MePBO）和不同的膦配体PPH ₃ ( 1 )，m-Tol ₃ P( 2 )和POP( 3 )，(PPh ₃ =三苯基膦，m-Tol ₃P=三(3-甲基苯基)膦，POP=双[2-(二苯基膦基)苯基]醚)，分别。所有配合物均通过单晶 X 射线衍射、光谱分析（IR、UV-Vis）、元素分析和光致发光研究进行表征。单晶X射线衍射分析表明，复合物1 - 3均采用离散阳离子配合物结构，其具有四面体寸₂ P ₂具有不同P-Cu-P合金的角度协调的几何形状。它们的紫外-可见吸收光谱在 P-Cu-P 角从3到2再到1的放大下表现出蓝移序列。PL 发射峰值波长为1 – 3也呈现类似的蓝移序列（3 → 1 / 2）。它们的微秒 PL 寿命表明它们的 PL 行为属于磷光。TD-DFT计算和波函数分析照射的S ₁和T ₁的状态的1 - 3都应该被指定为（ML + L'L）CT的状态。它们的 UV-Vis 吸收和磷光应归因于从 P-Cu-P 段到 MePBO 配体的电荷转移。因此，随着 P-Cu-P 角的增加（较低的 HOMO），S ₁和 T ₁的能量随着 PL 颜色的变化，状态也会增加。此外，膦配体取代基的空间位阻以及超强的分子内 π-π 堆积相互作用应有效抑制非辐射衰变，从而观察到异常的 PL 发射蓝移从1到2。