Unusual Aggregation/Gelation-Induced Phosphorescence of Propeller-type Binuclear Platinum(II) Enantiomers

Fei Gou, Jinghui Cheng, Xiaohong Zhang, Guangyu Shen, Xiangge Zhou, and Haifeng Xiang*

European Journal of Inorganic Chemistry, Eur. J. Inorg. Chem. 2016, 4862–4866.

Three binuclear cyclometalated Pt(II) complexes, [(ppy)Pt(m-SA)Pt(ppy)] (ppy = 2-phenylpyridine, SA =salicylaldehyde azine), have been synthesized and characterized. Owing to the blockageof intramolecular rotation of bridging SA ligands, all the complexes exhibit propeller-type enantiomers and aggregation-induced phosphorescence consequently. Interestingly, one complex with -NEt₂ groups instead of long alkyl chains, amide, urea peptides,cholesterol, sugar or steroidal groups was found to show strong phosphorescence enhancement gated by the gelation process. This unusual gelation behaviour is rarely encountered, as the metallogel has no any intermolecular hydrogen bonding and Pt-Pt interaction. We contribute the driving forces of gelation behaviour to its propeller-types tructure, optimally balanced solubility of -NEt₂ groups,enantiomer-induced p-p stacking interactions, and strong multiple intermolecular H-C, H-O, and H-H interactions.