Highly two-photon and X-ray excited long-persistent luminescence in a crystalline host-guest aggregate

Abstract

As a unique type of supramolecular self-assemblies, crystalline host-guest aggregates have attracted extensive interests in multiple application fields. Herein, a crystalline host-guest aggregate LIFM-HG1 was obtained with curcubit[8]uril as the host and carboxypyridinium salt as the guest. Single-crystal structural analysis indicates that the presence of abundant weak interactions in LIFM-HG1 provides a rigid environment for the guest molecule and effectively blocks the external quenchers. Spectral analysis and theoretical calculations confirm the presence of robust triplet energy levels in LIFM-HG1. Even more impressively, the intersystem crossing channels of the guest molecules are greatly opened up after the formation of the crystalline host-guest aggregate, resulting in a large k_isc of 6.70 × 10⁷ s⁻¹ at room temperature for LIFM-HG1 (which is ∼0 for pure guest), leading to fascinatingmultichannel (including one-photon, two-photon, and X-ray) excited LPL properties. In addition, the crystalline LIFM-HG1 has a much higher triplet state luminescence efficiency under X-ray and two-photon excitation than that under single-photon excitation (A_P/A_F = 86.8, 44.8, 10.7 under the three circumstances, respectively). And the phosphorescent emission intensity of LIFM-HG1 is 27.6 times higher than that of the crystalline guest under X-ray excitation. As a result, LIFM-HG1 shows a long afterglow retention time under both single- and two-photon excitation, and an impressive afterglow retention time of 1 s under X-ray excitation. Furthermore, the excellent lysosomal targeting and low cytotoxicity by the formation of host-guest aggregate makes LIFM-HG1 promising to be used as a novel lysosomal-targeted two-photon excited phosphorescent tracer.

Keywords

crystalline host-guest aggregate / long-persistent luminescence / two-photon / X-ray excited

RIGHTS & PERMISSIONS

2023 2023 The Authors. Aggregate published by South China University of Technology; AIE Institute and John Wiley & Sons Australia, Ltd.