Kromer Sarah, Roy Subhangi, Yarnell James E, Taliaferro Chelsea M, Castellano Felix N
Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA.
Dalton Trans. 2023 Mar 28;52(13):4008-4016. doi: 10.1039/d3dt00348e.
Dinuclear d Pt(II) complexes, where two mononuclear square planar Pt(II) units are bridged in an "A-frame" geometry, possess photophysical properties characterised by either metal-to-ligand-(MLCT) or metal-metal-ligand-to-ligand charge transfer (MMLCT) transitions determined by the distance between the two Pt(II) centres. When using 8-hydroxyquinoline (8HQH) as the bridging ligand to construct novel dinuclear complexes with general formula [C^NPt(μ-8HQ)], where C^N is either 2-phenylpyridine (1) or 7,8-benzoquinoline (2), triplet ligand-centered (LC) photophysics results echoing that in a mononuclear model chromophore, [Pt(8HQ)] (3). The lengthened Pt-Pt distances of 3.255 Å (1) and 3.243 Å (2) results in a lowest energy absorption centred around 480 nm assigned as having mixed LC/MLCT character by TD-DFT, mirroring the visible absorption spectrum of 3. Additionally, 1 and 2 exhibit LC photoluminescence with limited quantum yields (0.008) from broad transitions centred near 680 nm. Photoexcitation of 1-3 leads to an initially prepared excited state that relaxes within 15 ps to a LC excited state centred on the 8HQ bridge, which then persists for several microseconds. All the experimental results correspond well with DFT electronic structure calculations.
双核二价铂（II）配合物中，两个单核平面正方形铂（II）单元以“A 形”几何结构桥连，其光物理性质由两个铂（II）中心之间的距离决定，表现为金属到配体的电荷转移（MLCT）或金属-金属-配体到配体的电荷转移（MMLCT）跃迁。当使用 8-羟基喹啉（8HQH）作为桥连配体来构建通式为[C^NPt(μ-8HQ)]的新型双核配合物时，其中 C^N 为 2-苯基吡啶（1）或 7,8-苯并喹啉（2），三线态配体中心（LC）光物理结果与单核模型发色团[Pt(8HQ)]（3）中的情况相似。1 的铂-铂距离延长至 3.255 Å，2 的铂-铂距离延长至 3.243 Å，这导致最低能量吸收集中在 480 nm 左右，通过 TD-DFT 确定其具有混合 LC/MLCT 特征，与 3 的可见吸收光谱相似。此外，1 和 2 表现出 LC 光致发光，从以 680 nm 附近为中心的宽跃迁中获得有限的量子产率（0.008）。对 1 - 3 进行光激发会产生一个初始制备的激发态，该激发态在 15 ps 内弛豫到以 8HQ 桥为中心的 LC 激发态，然后持续数微秒。所有实验结果与 DFT 电子结构计算结果吻合良好。
