Clustering-triggered emission strategy towards tunable multi-color persistent phosphorescence
A clustering-triggered emission (CTE) strategy, namely the formation of heterogeneous clustered chromophores and conformation rigidification, for achieving tunable multicolor phosphorescence in single-component compounds is proposed. Nonconventional luminophores comprising of mere oxygen functionalities and free of π-bonding, i.e. D-(+)-xylose (D-Xyl), pentaerythritol (PER), D-fructose (D-Fru) and D-galactose (D-Gal), were adopted as a simple model system with explicit structure and molecular packing to address the hypothesis. Their concentrated solutions and crystals at 77 K or ambient conditions demonstrate remarkable multicolor phosphorescence afterglows in response to varying excitation wavelengths, owing to the formation of diverse oxygen clusters with sufficiently rigidified conformations. The intra- and intermolecular O…O interactions were definitely illustrated by both single crystal structure analysis and theoretical calculation. These findings shed new lights on the origin and facile achievement of tunable multicolor phosphorescence in single-component pure organics, and afford strong implications to the emission mechanism of nonconventional luminophores in turn.