Design And Synthesis Of Organic Phosphorescent Materials With Aggregation-induced Phosphorescence Based On Phenylphosphonium And Phenylsulfide And Their Applications In Sensing

Aggregation-induced luminescence refers to a photophysical phenomenon in which an organic molecule emits weak light in a solution but its luminescence is remarkably enhanced in aggregate state or solid state.Since the property of organic aggregation-induced luminescence materials can effectively overcome the problem of fluorescence quenching caused by the aggregation of traditional organic fluorescent dyes,they have broad application prospects in the fields of solid-state photovoltaic devices,chemical sensing and biological imaging.At present,the aggregation-induced luminescence organic materials have made great progress,and the fluorescent molecular probes from the visible to the near-infrared full-spectrum emission have been realized through structural design;however,most of the current aggregation-induced luminescent organic probes are short-lived.Fluorescent probes,therefore,are unable to effectively eliminate or attenuate autofluorescence and stray light from biological systems in combination with time-gated luminescence techniques.However,due to the limitation of spin law,the design of organic room temperature phosphorescent materials has great difficulties and challenges.In this context,the combination of aggregation-induced luminescence and organic room temperature phosphorescence is expected to achieve long-lived high-efficiency room temperature organic phosphorescence.The development of long-lived aggregation-induced organic phosphorescent materials will provide a superior class of probes for time-gated luminescence imaging.Long-life phosphorescent probes enable ultra-sensitive detection and super-resolution imaging in complex biological systems by eliminating autofluorescence.In this paper,we propose a design rule for organic phosphorescent materials based on the electronic acceptor-electron donor modularization,and prepare a variety of organic aggregation-inducedphosphorescence materials based on tetraphenylphosphonium and polysubstituted phenylene sulfide benzene compounds.The introduction of groups has developed a variety of phosphorescence enhancement methods for important ions such as iodide,perchlorate and calcium ions,and combined with time-gated luminescence technology to achieve sensitive detection and super-resolution imaging of these ions in complex biological systems.This article is divided into the following three parts:?1?It is very challenging to acquire pure organic materials with bright phosphorescence because of the lack of valid design strategies.Herein,we report an effective and general design strategy to achieve highly efficient phosphorescence of organic crystals by exploring and analyzing extremely distinct photoluminescence behaviors of tetraphenylphosphonium halides depending on different halide anions.Crystal structural analysis reveals ultralong organic afterglow is promoted by strong intermolecular electronic coupling in specific crystals.The extremely bright phosphorescence of tetraphenylphosphonium iodide?TPP I?and theoretical analysis demonstrate that the tremendous boost of the phosphorescence is caused by the coupling effects of significant heavy atom effect from iodine atoms and a small energy difference between the first singlet and triplet states in the crystal.Both the involvement of heavy iodide ions and accessible ionic interaction-induced organic crystals contribute to the accomplishment of a very high phosphorescence quantum yield?0.42?for TPP I.This specific iodide-triggered bright organic phosphorescence enables the development of a first time-gated detection method for iodide ion in the luminescence turn-on manner,and further offers an opportunity to establish a smart platform controlled by external stimuli.Excellent performance of this probe in imaging iodide in live cells and intriguing use in double encryption illustrate versatile and broad application prospects of highly efficient organic ionic crystals in various areas.?2?It is a formidable challenge to achieve highly efficient organic afterglow and readily tune transient and persistent phosphorescence of organic materials because of the lacking valid design principles for organic room-temperature phosphorescence and unknown generation mechanism of organic afterglow.Herein,we report the regulation of transient and persistent room-temperature phosphorescence of organic ionic crystals containing tetraphenyphosphonium?TPP?cations by the alteration of anions,and unique size-depending ultalong afterglow of tetraphenylphosphonium perchlorate?TPP ClO₄?crystals at ambient conditions.Three organic ionic crystals show sharply distinct triplet emissions based on three heavy-atom free anions due to enormous promotion from the first excited state to its neighboring triplet state by proper construction of donor-acceptor pattern in the crystals.TPP ClO₄ crystals not only exhibit ultrabright transient phosphorescence but also equivalently bright afterglow lasting for several seconds after ceasing the irradiation with an ultrahigh phosphorescence quantum yield of 0.56.The gradual intensifying of the afterglow with its crystal size proves the generation of ultralong afterglow from aggregates with strong intermolecular interactions in the crystals.Simultaneous boost of transient and persistent phosphorescence of TPP ClO₄ enables the development of sensitive detection and imaging of perchlorate in vivo,and offers the opportunity of time-dimensional anti-counterfeiting of school badges and banknote.These results greatly contribute to the general design principles of highly efficient room-temperature phosphorescence and their regulations by rational design.?3?The spatial and temporal monitoring of calcium ion mainly relies on fluorescent molecular probes currently;however,poor photostability of most Ca²⁺probes are not suited for long-term live-cell imaging.Herein,we designed a molecular probe with aggregation-induced phosphorescence?AIP?property for calcium ion-specific detection and imaging in vivo.The probe CaP1 was designed based on an AIPgen with a new recognition unit differing with the traditional1,2-bis?o-aminophenoxyl?ethane-N,N,N'N'-tetraacetic acid?BAPTA?group and iminodiacetate group.This recognition unit consisting of cyan and carboxylic acid groups shows specificity to calcium ions as highly as those of the traditional probes possess.The long-lived phosphorescence caused by calcium-triggered aggregation enables to establish a first time-gated detection method for calcium ions.The excellent imaging performance of CaP1 in Arabidopsis thaliana demonstrates that CaP1 has the same capability of monitoring calcium ions in live-cell imaging,and furthermore CaP1 exhibits much better photostability than Fluo 4-Am and thereby greater potential in long-term imaging.