Department of Chemistry and the Manitoba Institute for Materials , University of Manitoba , 144 Dysart Road , Winnipeg , Manitoba R3T 2N2 , Canada.
Department of Chemistry , Durham University , Durham , DH1 3LE , United Kingdom.
Inorg Chem. 2018 May 7;57(9):4966-4978. doi: 10.1021/acs.inorgchem.7b03223. Epub 2018 Apr 12.
Benzannulated bidentate pyridine/phosphine ( P^N) ligands bearing quinoline or phenanthridine (3,4-benzoquinoline) units have been prepared, along with their halide-bridged, dimeric Cu(I) complexes of the form ( P^N)Cu. The copper complexes are phosphorescent in the orange-red region of the spectrum in the solid-state under ambient conditions. Structural characterization in solution and the solid-state reveals a flexible conformational landscape, with both diamond-like and butterfly motifs available to the CuX cores. Comparing the photophysical properties of complexes of (quinolinyl)phosphine ligands with those of π-extended (phenanthridinyl)phosphines has revealed a counterintuitive impact of site-selective benzannulation. Contrary to conventional assumptions regarding π-extension and a bathochromic shift in the lowest energy absorption maxima, a blue shift of nearly 40 nm in the emission wavelength is observed for the complexes with larger ligand π-systems, which is assigned as phosphorescence on the basis of emission energies and lifetimes. Comparison of the ground-state and triplet excited state structures optimized from DFT and TD-DFT calculations allows attribution of this effect to a greater rigidity for the benzannulated complexes resulting in a higher energy emissive triplet state, rather than significant perturbation of orbital energies. This study reveals that ligand structure can impact photophysical properties for emissive molecules by influencing their structural rigidity, in addition to their electronic structure.
苯并双齿吡啶/膦（P^N）配体带有喹啉或菲啶（3,4-苯并喹啉）单元，以及它们的卤化物桥联的二聚铜（I）配合物(P^N)Cu。在环境条件下，铜配合物在固态中在橙红色光谱区域具有磷光。在溶液中和固态中的结构表征揭示了一个灵活的构象景观，CuX 核具有钻石状和蝴蝶状两种构象。比较（喹啉基）膦配体的配合物的光物理性质与π-扩展（菲啶基）膦的配合物的光物理性质，揭示了苯并环化的反直觉影响。与关于π-扩展和最低能量吸收最大值红移的传统假设相反，对于具有较大配体π-体系的配合物，发射波长观察到近 40nm 的蓝移，这归因于磷光，基于发射能量和寿命。比较从 DFT 和 TD-DFT 计算优化的基态和三重激发态结构，将这种效应归因于苯并环化配合物的刚性更大，导致更高能量的发射三重态，而不是轨道能量的显著扰动。这项研究表明，配体结构可以通过影响其结构刚性来影响发光分子的光物理性质，而不仅仅是其电子结构。
