Enhanced Emission in Self‐Assembled Phenyleneethynylene Derived π‐Gelators

Abstract

Optical properties of π‐systems are of great significance for a wide range of applications in materials and biology. Aggregation and self‐assembly induced emission are one of such phenomena. Herein, the self‐assembly induced modulation of the emission of p‐phenyleneethynylene (PE) chromophores bearing linear achiral (1) or branched chiral (2) alkoxy chains is reported. Self‐assembled structures of both 1 and 2 from n‐decane exhibit enhanced emission with fluorescence quantum yield (ΦF) values of 0.34 and 0.25, respectively, whereas these molecules are less‐emissive in chloroform (ΦF = 0.02). Transmission electron microscopy and fluorescence microscopy studies reveal the formation of entangled blue‐emissive fibers for 1 and supercoiled helical blue‐emissive fiber bundles for 2. At higher concentrations (8.8 × 10−3 m for 1 and 23.6 × 10−3 m for 2) in n‐decane, intense blue‐emitting gels are formed. Significant shift in the emission toward longer wavelength can be seen from solution state to aggregates to the gel state. The wide‐angle X‐ray scattering and fluorescence data indicate that the interdigitated lamellar assembly with weaker π‐stacking and the resultant restriction of rotation of the PE chromophores are responsible for the enhanced emission of the self‐assembled gel state.

Tweaking a BODIPY Spherical Self‐Assembly to 2D Supramolecular Polymers Facilitates Excited‐State Cascade Energy Transfer

“…Upon gradual reduction in temperature from 363 to 283 K, the intensity of the absorption maximum was reduced and the absorption spectrum corresponding to both BODIPY and phenyleneethynylene part became broad (Figure S3a). In contrast, the temperature‐dependent emission studies showed a gradual increase in the intensity when 1 in MCH was cooled from 363 to 283 K, indicating aggregation‐induced enhanced emission behavior (Figure S3b) [2a, 21a] . Since the phenyl ring attached at the meso position of BODIPY chromophore 1 is unsubstituted, rotational and vibrational motions are facilitated at higher temperature, leading to non‐radiative deactivation of the excited state and less emission [20a] .…”

“…Fourier transform‐infrared (FT‐IR) studies have shown that the 2D sheets formed in n ‐decane are stabilized by various non‐covalent interactions (Figure S15). Film state FT‐IR spectrum of 1 obtained from n ‐decane exhibited bands at 3288, 1640 and 1545 cm −1 , suggesting intermolecular H‐bonding [12b, 21a] . On the other hand, the BODIPY 1 in CDCl 3 displayed two bands at 3450 and 3348 cm −1 , assigned as amide A bands.…”

Poly(l-lactide)s with tetraphenylethylene: role of polymer chain packing in aggregation-induced emission behavior of tetraphenylethylene

“…17,18,20–23 This unusual phenomenon has been extensively studied in recent years using many AIE molecules such as tetraphenylethylenes, silole, stilbenes, distyrylanthracene, phenyleneethylenes, etc . 1,23–34 Among these, tetraphenylethylene (TPE) and its derivatives have been widely used to understand the fundamental emissive mechanism. The free rotation of the phenyl rings and partial twisting of the CC bond in TPE lead to the fast nonradiative decay and quench the fluorescence emission in dilute solutions.…”

“…20,22,25,34,36–40 Owing to the structural diversity, the AIE properties of chromophores in these hybrid systems can be tuned in response to external stimuli such as light, heat, pH, solvents, etc . 11,24,28,34,36,37,41 The emission properties of these hybrid materials are sensitive to the packing structure and aggregation of fluorescent molecules. For example, the importance of molecular design in controlling the photophysical and optoelectronic behaviors is investigated in several star-shaped polymers for various applications.…”

Understanding the role of conjugation length on the self-assembly behaviour of oligophenyleneethynylenes

“… 1 Particularly, linear oligomeric π-systems have attracted widespread attention by virtue of their exceptional optical and electronic properties. 2 Examples thereof include oligophenylenes (OPs), 3 oligophenylenevinylenes (OPVs), 4 oligophenyleneethynylenes (OPEs), 5 oligoanilines (OAs) 6 and oligothiophenes. 7 Among them, OPEs have been particularly employed because of their excellent photophysical and electronic properties, which have been exploited for many interesting applications, such as light emitting diodes (LEDs), 8 field-effect transistors (FETs), 9 organic photovoltaic devices, 10 sensing, 11 imaging 12 and thermoelectric materials.…”