Aggregation and Tunable Color Emission Behaviors of l‐Glutamine‐Derived Platinum(II) Bipyridine Complexes by Hydrogen‐Bonding, π–π Stacking and Metal–Metal Interactions

• Published in: Chemistry : a European journal 2019-04, Vol.25 (20), p.5251-5258
• Main Authors: Ai, Yeye, Li, Yongguang, Fu, Heidi Li‐Ki, Chan, Alan Kwun‐Wa, Yam, Vivian Wing‐Wah
• Format: Article
• Language: English
• Subjects: Agglomeration; Chemistry; Disruption; Emissions; Excimers; Functional groups; gels; Glutamine; Honeycomb construction; Hydrogen; Metals; Morphology; Nanospheres; NMR; Nuclear magnetic resonance; photophysics; Platinum; self-assembly; Solvents; Stacking; Temperature effects
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201805901

An l‐glutamine‐derived functional group was introduced to the bis(arylalkynyl)platinum(II) bipyridine complexes 1–4. The emission could be switched between the 3MLCT excited state and the triplet excimeric state through solvent or temperature changes, which is attributed to the formation and disruption of hydrogen‐bonding, π–π stacking, and metal–metal interactions. Different architectures with various morphologies, such as honeycomb nanostructures and nanospheres, were formed upon solvent variations, and these changes were accompanied by 1H NMR and distinct emission changes. Additionally, yellow and red emissive metallogels were formed at room temperature due to the different aggregation behaviors introduced by the substituent groups on bipyridine. The thermoresponsive metallogel showed emission behavior with tunable colors by controlling the temperature. The negative Gibbs free‐energy change (ΔG) and the large association constant for excimer formation have suggested that the molecules undergo aggregation through hydrogen‐bonding, π–π, and metal–metal interactions, resulting in triplet excimeric emission. A series of bis(arylalkynyl) platinum(II) complexes with l‐glutamine‐derived functional group was investigated. These complexes show various spectroscopic properties and aggregation behaviors. The emission could be switched between the 3MLCT excited state and the triplet excimeric state through different solvents or temperatures; the changes were attributed to the formation and disruption of hydrogen‐bonding, π–π stacking and metal–metal interactions. The formed thermoresponsive metallogel showed emission behavior with tunable colors by controlling the temperature. The negative Gibbs free‐energy change (ΔG) and the large association constant for excimer formation suggest that the molecules undergo aggregation through hydrogen‐bonding, π–π stacking and metal–metal interactions, resulting in triplet excimeric emission.