Intrinsic and Extrinsic Heavy-Atom Effects on the Multifaceted Emissive Behavior of Cyclic Triimidazole |
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Authors: | Dr Elena Lucenti Dr Alessandra Forni Dr Chiara Botta Dr Clelia Giannini Dr Daniele Malpicci Dr Daniele Marinotto Dr Andrea Previtali Dr Stefania Righetto Prof Elena Cariati |
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Institution: | 1. ISTM-CNR, INSTM RU, Via Golgi 1, 20133 Milano, Italy;2. ISMAC-CNR, INSTM RU, Via Corti 12, 20133 Milano, Italy;3. Department of Chemistry, Università degli Studi di Milano and INSTM RU, Via Golgi 19, 20133 Milano, Italy |
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Abstract: | Considering that heavy halogen atoms can be used to tune the emissive properties of organic luminogens, the understanding of their role in photophysics is fundamental for materials engineering. Here, the extrinsic and intrinsic heavy-atom effects on the photophysics of organic crystals were separately evaluated by comparing cyclic triimidazole ( TT ) with its monoiodo derivative ( TTI ) and its co-crystal with diiodotetrafluorobenzene ( TTCo ). Crystals of TT showed room-temperature ultralong phosphorescence (RTUP) originated from H-aggregation. TTI and TTCo displayed two additional long-lived components, the origin of which is elucidated through single-crystal X-ray and DFT/TDDFT studies. The results highlight the different effects of the I atom on the three phosphorescent emissions. Intrinsic heavy-atom effects play a major role on molecular phosphorescence, which is displayed at room temperature only for TTI . The H-aggregate RTUP and the I⋅⋅⋅N XB-induced (XB=halogen bond) phosphorescence on the other side depend only on packing features. |
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Keywords: | co-crystals halogen bonding phosphorescence photophysics time-resolved spectroscopy |
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