Ionization and Anion−π⁺ Interaction: A New Strategy for Structural Design of Aggregation-Induced Emission Luminogens

Abstract

Recent years have witnessed the significant role of anion-π interactions in many areas, which potentially brings the opportunity for the development of aggregation-induced emission (AIE) systems. Here, a new strategy that utilized anion-π interactions to block detrimental π-π stacking was first proposed to develop inherent-charged AIE systems. Two AIE-active luminogens, namely, 1,2,3,4-tetraphenyloxazolium (TPO-P) and 2,3,5-triphenyloxazolium (TriPO-PN), were successfully synthesized. Comprehensive techniques such as single-crystal analysis, theoretical calculation, and conductivity measurement were used to illustrate the effects of anion-π interactions on the AIE feature. Their analogues tetraphenylfuran (TPF) and 2,4,5-triphenyloxazole (TriPO-C) without anion-π interactions suffered from the aggregation-caused emission quenching in the aggregate state, demonstrating the important role of anion-π interactions in suppressing π-π stacking. TriPO-PN was biocompatible and could specifically target lysosome in fluorescence turn-on and wash-free manners. This suggested that it was a promising contrast agent for bioimaging.

Strong Solid‐state Luminescence Enhancement in Supramolecular Assemblies of Polyoxometalate and “Aggregation‐Induced Emission”‐active Phospholium

“…Thisn ovel strategy takes advantage of both the size of the POMs and their highly nucleophilic oxygen surfaces to jointly block p-p stacking interactions between the cationic luminophores andt o drastically restrictt heir intramolecular motions, via numerous noncovalent interactions. [5] Besides, considering that POMs can also exhibit intrinsic photophysical properties, these new results thus pave the way toward novel multifunctional hybrid materials.…”

“…This nicely extends the scopeo f anion-p + engineering to develop solid-state emitters. [5] Finally, as POMs can also exhibit intrinsic photoactive, redox or magnetic properties, this work opens the way towardst he design of novel multifunctional hybrid systems.…”

“…For example, Ta ng et al recently reported that anion-p + interactions between cationic AIE-oxazoliums and classical PF 6 À counter-ionsacting as spacers efficiently reduces the detrimental ACQ effect. [5] In this context, p-conjugated P-heterocycles [6] such as phospholiums appear as promising cationic P-emitters to furthere xtend this approachb ecause they can also exhibit AIE activity when ionically assembled with usual counter-ions (Cl À ,B F 4 À ,O Tf À ). [7,8] To go furtheri nd irecting favorably the AIE/ACQ balance in these moleculars ystems, the use of highly nucleophilic anions able to develop strong H-bonding interactions with phospholiums could be envisioned to strengthen their rigidity,a nd hence to exalt the AIE effect.…”

Time-dependent Photodynamic Therapy for Multiple Targets: A Highly Efficient AIE-active Photosensitizer for Selective Bacterial Elimination and Cancer Cell Ablation

“…We were initially motivated by the influence of anion-p + interactions on triggering the AIE effect, [10] and consequently, we designed and prepared an AIE-based PS called 4TPA-BQ by ao ne-step synthesis.T he inherent positive charge of 4TPA-BQ endows the molecule with modest water solubility for bioapplications.S imultaneously,4 TPA-BQ demonstrates an aggregation-induced ROS generation (AIROSG) effect, with a 1 O 2 quantum yield up to unity.U nprecedentedly, time-dependent PDT for multiple targets was achieved by controlling the incubation time of 4TPA-BQ with various targets.O ni rradiation with white light for 15 minutes, 4TPA-BQ eliminated drug-resistant E. coli infection efficiently,l eaving host tissues unaffected. When the incubation time was lengthened to 12 hours,4 TPA-BQ was able to kill cancer cells with only slight harm to normal cells (Scheme 1).…”

Bis‐Naphthalene Cleft with Aggregation‐Induced Emission Properties through Lone‐Pair⋅⋅⋅π Interactions

“…[5] New noncovalenti nteractionsw ould lead to new AIEgens.F or example,K im and co-workers [6] reportedahalogenated aromatic carbonyl compound that showss urprisingly efficient solid-statep hosphorescence. This was attributedt or estricted molecular motion in the solid state through strong intermolecular halogen bonds;T ang and co-workers [7] reported an inherently charged AIEgen whose luminescence in the solid state was achieved through anion···p + interactions to restrict the intramolecular motionsa nd block the detrimental p···p stacking.…”