Fine Tuning of Emission Behavior, Self-Assembly, Anion Sensing, and Mitochondria Targeting of Pyridinium-Functionalized Tetraphenylethene by Alkyl Chain Engineering

Abstract

Compared to the many studies that focus on the development of novel molecular frameworks pertaining to functionalized fluorescent materials, there is lesser emphasis on side chains even though they have a significant impact on the properties and applications of fluorescent materials. In this study, a series of pyridinium-functionalized tetraphenylethene salts (TPEPy-1 to TPEPy-4) possessing different alkyl chains are synthesized, and the influence of chain length on their optical performance and applications is thoroughly investigated. By changing the alkyl chain, the fluorogens exhibit opposite emission behavior in aqueous media because of their distinct hydrophobic nature, and their solid-state emission can be fine-tuned from green to red owing to their distinct molecular configuration. In addition, by increasing the chain length, the microstructure of the self-assembled fluorogens converts from microplates to microrods with various emission colors. Moreover, TPEPy-1 exhibits dual-mode fluorescence “turn-on” response toward NO3 – and ClO4 – in aqueous media because the anions induce the self-assembly of fluorogens. Furthermore, the fluorogens display cellular uptake selectivity while the proper alkyl chain impels the fluorogens to penetrate the cell membrane and accumulate in the mitochondria with high specificity.

A side-chain engineering strategy for constructing fluorescent dyes with direct and ultrafast self-delivery to living cells

“…In addition, some piecemeal reports also indirectly supported the applicability of the SCES we have proposed. [37][38][39] For example, in a previous study, we found that the molecule LAD-1 with methyl always needs a longer time to enter cells in comparison to the molecule LAD with butyl. 36 Moreover, commercial probes such as TMRM and TMRE with two methyls can cross the plasma membrane more rapidly than rhodamine 123 without an alkyl chain.…”

Self‐Assembly of Aggregation‐Induced‐Emission Molecules

“…Recently, Zhao and Tang et al. reported that changes to the alkyl chain length can be an approach to manipulate the self‐assembly of AIEgens . They synthesized a series of pyridinium‐functionalized TPE salts (TPEPy) with different alkyl chains (Figure ).…”

“… Effect of alkyl chain length on the self‐assembly, emission, anion detection, and cell imaging of TPEPy‐ n ( n =1, 4, 7, 10) …”

“…Recently,Z hao and Ta ng et al reported that changes to the alkyl chain length can be an approacht om anipulate the selfassemblyo fA IEgens. [13] They synthesized as eries of pyridinium-functionalized TPE salts (TPEPy) with different alkyl chains ( Figure 4). As the alkyl chain length was increased, the self-assembled structure changed from microplates to microrods, and the emission color was blueshifted from red to green.…”

“…Effect of alkyl chainlength on the self-assembly,emission, anion detection,a nd cell imagingofT PEPy-n (n = 1, 4, 7, 10). [13] Figure 6a is an example of the introductiono fA IEgensi nto an amphiphilic block copolymer through RAFT polymerization. [19b] Ac rosslinkable AIE dye (R-E) with two vinyl end groups was copolymerized with the amphiphilic monomer PEGMA.T he resultant copolymer showed typical amphiphilic properties.…”