Transformation of Nonporous Adaptive Pillar[4]arene[1]quinone Crystals into Fluorescent Crystals via Multi-Step Solid–Vapor Postsynthetic Modification for Fluorescence Turn-on Sensing of Ethylenediamine

Abstract

Organic solid-state fluorescent crystals have received extensive attention owing to their remarkable and promising optoelectronic applications in many fields. Current methods to obtain organic fluorescent crystals usually involve two steps: (1) solution phase organic synthesis and (2) crystallization of target fluorescent compounds. Direct transformation from nonfluorescent organic crystals to fluorescent organic crystals by postsynthetic modification (PSM) might be a potential alternative to the traditional methods. Although it is common to implement PSM for porous frameworks, it remains a huge challenge for nonporous organic crystals. Herein, we report a novel method of multistep solid−vapor PSM in nonporous adaptive crystals (NACs) of a pillar[4]arene[1]quinone (M1) to prepare organic solid-state fluorescent crystals. Fluorescent organic crystals can be simply generated when guest-free M1 crystals were exposed to ethylenediamine (EDA) vapor. However, only nonemissive crystals of a thermodynamically metastable intermediate M2 are obtained through solid−vapor single-crystal-to-single-crystal transformation of CH 3 CN-loaded M1 crystals. Solution-phase reaction of M1 with EDA affords three distinct compounds with different fluorescent properties, which are demonstrated to be the main components of the fluorescent organic crystals that are generated by the solid− vapor PSM. Mechanistic studies show that the pillararene skeleton not only induces the solid−vapor PSM by physical adsorption of EDA but also facilitates the fluorescent emission in the solid state by restricting intermolecular π−π interactions to avoid aggregation-caused quenching (ACQ). Furthermore, this interesting phenomenon is applied for facile fluorescence turn-on sensing of EDA vapor to distinguish EDA from other aliphatic amines.

Solvent-Driven Chirality Switching of a Pillar[4]arene[1]quinone Having a Chiral Amine-Substituted Quinone Subunit

“…Despite the CD signals at 310 nm, new Cotton effects appeared in the region of 300–400 nm of 1a and 2a , which could be ascribed to the transition of 2,5-bis(alkyl/arylamino)-1,4-benzoquinones ( Martini and Nachod, 1951 ; Li et al, 2020 ). In addition, strong Cotton effects in CT transition in the wavelength region of 400–700 nm were observed ( Wang H. J. et al, 2020 ).…”

“…Synthesis of chiral pillar[5]arenes without the complicated chiral resolution processes should be more convenient and valuable for studying supramolecular chirality switching. It has been reported that 1,4-benzoquinone undergoes the Michael addition reaction with aliphatic or aromatic amines to selectively afford 2,5-bis(alkyl/arylamino)-1,4-benzoquinones ( Almeida Barbosa et al, 2010 ; Strutt et al, 2014a ; Li et al, 2018 ; Kiruthika et al, 2020 ; Li et al, 2020 ). In this work, we report the synthesis of several new chiral pillar[4]arene[1]quinone derivatives and their unique chiroptical properties.…”

Pagoda[5]arene with Large and Rigid Cavity for the Formation of 1∶2 Host–Guest Complexes and Acid/Base-Responsive Crystalline Vapochromic Properties

“…The development of new macrocyclic hosts has enriched the scope of vapochromic crystals in recent years. [56][57][58][59][60] The special feature of supramolecular vapochromic crystals is that the vapor-responsive detection can be achieved by changing the host-guest interactions. Based on the presence or absence of ICT interaction between P5 and G1 and from weak to strong ICT interaction between P5 and G10, obvious acid/base-responsive switchable processes with color changes visible to the naked eye could be achieved in solution.…”

Fluorescence-Based Sensing of Pesticides Using Supramolecular Chemistry

“…They are similar to calixarenes, but the linkages between the phenols lead to pillar-like, highly symmetrical structures (Behera et al, 2020). Pillararenes have been used in a variety of supramolecular applications, including for the binding and removal of organic toxicants from contaminated aqueous environments (Fernando et al, 2019); as components of solidstate crystalline structures (Li et al, 2020a); and as nanochannels for biomimetic research (Sun et al, 2020). Like the macrocycle classes previously discussed, pillararenes rely primarily on hydrophobic association to bind small-molecule hydrophobic guests (Shen et al, 2018), with particular examples reported using electrostatic interactions (Liu et al, 2019b) and/or intermolecular hydrogen bonding (Han et al, 2020a) as cooccurring mechanisms.…”