Polymerization Based on Modified ß-Cyclodextrin Achieves Efficient Phosphorescence Energy Transfer for Anti-Counterfeiting.

Supramolecular polymerization can not only activate guest phosphorescence, but also promote phosphorescence Förster resonance energy transfer and induce effective delayed fluorescence. Herein, the solid supramolecular assemblies of ternary copolymers based on acrylamide, modified ß-cyclodextrin (CD), and carbazole (CZ) are reported. After doping with polyvinyl alcohol (PVA) and dyes, a NIR luminescence supramolecular composite with a lifetime of 1.07 s, an energy transfer efficiency of up to 97.4% is achieved through tandem phosphorescence energy transfer. The ternary copolymers can realize macrocyclic enrichment of dyes in comparison to CZ and acrylamide copolymers without CD, which can facilitate energy transfer between triplet and singlet with a high donor-acceptor ratio. Additionally, the flexible polymeric films exhibit regulable lifetime, tunable luminescence color, and repeatable switchable afterglow by adjusting the excitation wavelength, donor-acceptor ratio, and wet/dry stimuli. The luminescence materials are successfully applied to information encryption and anti-counterfeiting.

Macrocycle γ-Cyclodextrin Confined Polymeric Chromophore Ultralong Phosphorescence Energy Transfer.

A multicolor persistent luminescence solid polymeric system based on macrocycle-confined phosphorescence energy transfer was constructed with γ-cyclodextrin (γ-CD) and poly(vinyl alcohol) modified by triphenylene derivative (TP-PVA). Attributed to the fact that macrocycles effectively suppress the aggregation of guests and form a rigid environment via coassembling with the polymer, the phosphorescence lifetime of the yielded polymeric films is prolonged from 0.22 to 5.84 s, accompanied by a visible afterglow of more than 1 min. Furthermore, upon doping with several commercial dyes, full-color afterglow emissions with a duration of more than 50 s are realized through phosphorescence energy transfer. Notably, the multicolor-emitting-afterglow materials are successfully exploited for noctilucent lighting and anticounterfeiting ink.

Two-Photon Excited Near-Infrared Phosphorescence Based on Secondary Supramolecular Confinement.

Organic phosphorescence materials have received wide attention in bioimaging for bio-low toxicity and large Stokes. Herein, a design strategy to achieve near-infrared (NIR) excitation and emission of organic room-temperature phosphorescence through two-stage confinement supramolecular assembly is presented. Via supramolecular macrocyclic confinement, the host-guest complexes exhibit phosphorescence with two-photon absorption (excitation wavelength up to 890 nm) and NIR emission (emission wavelength up to 800 nm) in aqueous solution, and further nano-confinement assembly significantly strengthens phosphorescence. Moreover, the nano-assemblies possess color-tunable luminescence spanning from the visible to NIR regions under different excitation wavelengths. Intriguingly, the prepared water-soluble assemblies maintain two-photon absorption and multicolor luminescence in cells or vivo.

Highly Reversible Supramolecular Light Switch for NIR Phosphorescence Resonance Energy Transfer.

Although purely organic room-temperature phosphorescence (RTP) has drawn widespread attention in recent years, regulatable phosphorescence resonance energy transfer (PRET) supramolecular switch is still rare. Herein, single molecular dual-fold supramolecular light switches, which are constructed by phenylpyridinium salts modified diarylethene derivatives (DTE-Cn, n = 3, 5) and cucurbit[8]uril (CB[8]) are reported. Significantly, biaxial [3]pseudorotaxane displayed efficiently reversible RTP after binding with CB[8] and the phosphorescence quenching efficiency is calculated up to be 99%. Furthermore, the binary supramolecular assembly can coassemble with Cy5 to form ternary supramolecular assembly showing efficiently PRET, which is successfully applied in switchable near infrared (NIR) mitochondria-targeted cell imaging and photocontrolled data encryption. This supramolecular strategy involving energy transfer provides a convenient approach for phosphorescent application in biology and material fields.

Supramolecular Purely Organic Room-Temperature Phosphorescence.

In recent years, purely organic room-temperature phosphorescence (RTP) has aroused wide concern and promotes the development of the supramolecular phosphorescence. Different from organic crystallization, polymerization, or matrix rigidification, supramolecular strategy mainly takes advantage of the synergy between supramolecular co-assembly and strong binding by macrocyclic host compounds (cucurbit[n]urils, cyclodextrins, etc.) to overcome deficiencies such as poor processability and water solubility and improves RTP materials' quantum efficiency and lifetime in the solid state or in an aqueous solution. Meanwhile, it expands application, especially in aqueous solution, in cell imaging. Therefore, supramolecular phosphorescence will become a new growth point and will have broad application prospects in chemistry, biology, and material science.This Account focuses on the uniquely synergetic advantages of co-assembly and host-guest interaction from macrocyclic hosts for enhancing RTP. This Account starts with a brief introduction of the recent development of organic RTP materials as well as the host-guest interaction and co-assembly. Then, we introduce a supramolecular solid-state RTP strategy involving an ultrahigh phosphorescent quantum yield via the tight encapsulation of macrocyclic host cucurbit[6]uril, an ultralong lifetime via changing the substituents of phosphors, and long-lived and bright RTP by the synergy of host-guest interaction and polymerization. Meanwhile, the applications of solid-state RTP materials for anti-counterfeiting and data encryption are presented. The third part will be the water-phase supramolecular phosphorescence systems constructed by water-soluble macrocyclic host cucurbit[8]uril. Host-guest interaction and polymerization worked together toward efficient phosphorescence in aqueous solution, and the multi-stage assembly promoted phosphorescent applications such as cell targeted imaging and energy transfer. A humidity sensor and data encryption by the conversion of supramolecular hydrogels and xerogels are also involved. In the summary section, we present perspectives and possible research directions for supramolecular phosphorescence.Furthermore, on the basis of previous research, we would like to conclude and propose the developing concept of "macrocycles enhance guest's phosphorescence", and this concept not only means that the macrocyclic host limits the movement of the guest compound or promotes interactions between guest compounds but also involves the synergetic enhancement centered on macrocyclic compounds via multi-stage supramolecular assembly which further improves the efficiency of RTP, water solubility, and biocompatibility. And we believe that this concept will be able, together with theory of "assembly-induced emission" and "aggregation-induced emission", to accelerate the development of purely organic RTP materials.

Supramolecular Pins with Ultralong Efficient Phosphorescence.

Constructing ultralong organic phosphorescent materials possessing a high quantum yield is challenging. Herein, assemblies of purely organic supramolecular pins composed of alkyl-bridged phenylpyridinium salts and cucurbit[8]uril (CB[8]) are reported. Different from "one host with two guests" and "head-to-tail" binding, the binding formation of supramolecular pins is "one host with one guest" and "head-to-head," which overcomes electrostatic repulsion and promotes intramolecular charge transfer. The supramolecular pin 1/CB[8] displays afterglow with high phosphorescence quantum yield (99.38%) after incorporation into a rigid matrix, which is the highest yield reported to date for phosphorescent materials. Moreover, multicolor photoluminescence can be obtained by different excitation wavelengths and ratios of host to guest. Owing to the redshift of the absorption, the supramolecular pins are applied for targeted phosphorescence imaging of mitochondria. This work will provide a reasonable supramolecular strategy to achieve redshifted and efficient phosphorescence both in the solid state and in aqueous solution.

A twin-axial pseudorotaxane for phosphorescence cell imaging.

A twin-axial pseudorotaxane is constructed using a phenylpyridine salt with diethanolamine (DA-PY) and cucurbit[8]uril (CB[8]), and it not only displays phosphorescence in aqueous solution but it can also be used for targeted cell-imaging.