Solid‐State TICT‐Emissive Cruciform: Aggregation‐Enhanced Emission, Deep‐Red to Near‐Infrared Piezochromism and Imaging In Vivo

Abstract

Near‐infrared piezochromic materials presenting fluorescence responses with clear color differences and good penetrability have important potential applications, but a few such organic compounds are developed. Twisted intramolecular charge transfer (TICT) emission is versatile in solutions, especially for preparing bio/chem‐sensing materials due to the excellent sensitivity of the emission to alterations in the external environment. By analogy, the solid‐state TICT‐emissive chromophores are probably excellent candidates for the environmentally responsive material. Herein, X‐shaped π architectures that exhibit solid‐state TICT emission are developed, and their luminescent chromism and bioimaging properties are investigated. Initially, the cruciform fluorophore exhibits anomalous aggregation‐enhanced emission (AEE) and dual emission due to the existence of a TICT state. Interestingly, TICT emission is observed even in the aggregated state because the spacious environment around the bulky triphenylamine allows for rotation. During the compression process, the TICT‐based fluorophore demonstrates deep‐red to near‐infrared piezochromic behavior with a remarkable redshift (162 nm) and high sensitivity (15.1 nm GPa−1). The bioimaging performance of the TICT‐emissive dye suggests its potential utility as a fluorescent probe for biological applications.

Switching Pathways of Triplet State Formation by Twisted Intramolecular Charge Transfer

“…Existence of dual emission from LA17b in polar solvents (including ethanol and hexane binary mixtures, see below) and strong red-shifted fluorescence together with long lifetimes in polar solvents (1.1 ns in ethanol) are argumentations for the ICT state being of twisted intramolecular charge transfer (TICT) character. − Similarity of TA spectra of the film with LA17b in hexane (where no TICT exists) is an additional proof for the above assignment. Similar phenomena have also been observed for other molecular twisted charge-transfer systems. ,− …”

TICT-Based Near-Infrared Ratiometric Organic Fluorescent Thermometer for Intracellular Temperature Sensing

“…These traditional organic fluorescent thermometers, however, usually resulted in an aggregation-caused quenching (ACQ) problem in a concentrated solution or solid state, resulting in a decrease in the fluorescence quantum yield, − whereas construction of a TICT fluorescence dye with a twisted structure may help in avoiding the ACQ effect because the large steric hindrances could reduce the intermolecular Π–Π interactions and even enhance the fluorescent emission via the restricted intramolecular motion mechanism to achieve aggregation-induced emission (AIE) in the aggregate state. − Near-infrared (NIR) fluorescent dyes in the 650–900 nm emission wavelength can efficiently reduce disturbance from biological tissue autofluorescence and acquire high detection penetration depth in bioimaging applications. Fluorescence dyes with twisted donor (D)–acceptor (A) structures can achieve far-red/NIR emission with TICT characteristics in aqueous solutions because polar solvents facilitated intramolecular electron delocalization, leading to the reduced band gap of molecules. − However, there is almost no study on the organic ratiometric fluorescent thermometer with AIE, TICT-based NIR emission, and temperature-dependent luminescence properties for cellular temperature sensing.…”

Fascinating Supramolecular Assembly through Noncovalent Interactions Involving Anions in Organic Ionic Crystals

“…According to the literature studies, − for π-stacking systems, the broadened and red-shifted absorption bands indicates the pressure-induced decrease in intermolecular distances and revolving of the molecular planes. These changes can further affect the intermolecular interactions in these ionic crystal systems.…”