Abstract
The aggregation behaviour of Au(I) complexes in condensed phases can affect their emission properties. Herein, aggregation-induced room-temperature phosphorescence (RTP) is observed from the crystals of trinuclear Au(I) complexes. The RTP is highly sensitive to the crystal structure, with a slight difference in the alkyl side chains causing not only a change in the crystal structure but also a shift in the RTP maximum. Furthermore, in nanocrystals, reversible RTP colour changes are induced by phase transitions between crystal polymorphs during crystal growth from solution or the pulverisation of bulk crystals. The colour change mechanism is discussed in terms of intermolecular interactions in the crystal structure of the luminescent aggregates. The results suggest that the behaviour in nanocrystals may differ from that in bulk crystals. These insights will advance the fundamental understanding of crystallisation mechanisms and may aid in the discovery of new materials properties for solids with nano- to micrometre sizes.
Highlights
The aggregation behaviour of Au(I) complexes in condensed phases can affect their emission properties
The crystal structures of some of the investigated Au complexes depend on the crystal size; the luminescence colour can be altered by varying the crystal size, allowing us to observe the early stage of the crystallisation process and the polymorphic behaviour during crystal growth
During observations of the room-temperature phosphorescence (RTP) behaviour in the CH2Cl2/methanol mixed solvent system to confirm the aggregation-induced emission (AIE) activity, we found that the RTP colour and spectrum of the complexes in the mixed solvent, in which small crystals were suspended, were considerably different from those of the bulk crystals prepared by conventional recrystallisation (Supplementary Note 1 and Supplementary Fig. 8)
Summary
The aggregation behaviour of Au(I) complexes in condensed phases can affect their emission properties. A fascinating feature of nanocrystals is the dependence of the materials properties on the crystal size, with drastic differences observed between single molecules and bulk states. We synthesise three Au complexes bearing alkyl side chains with slightly different lengths Using these complexes, we determine the relationship between the crystal structure and the luminescence properties in terms of the intermolecular interactions and utilise this relationship to investigate the crystallisation process from solution. The crystal structures of some of the investigated Au complexes depend on the crystal size; the luminescence colour can be altered by varying the crystal size, allowing us to observe the early stage of the crystallisation process and the polymorphic behaviour during crystal growth
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