Stimuli-Responsive Trimorphs and Charge-Transfer Complexes of a Twisted Molecular Donor

Abstract

Supramolecular self-assemblies and co-assemblies possess multiple noncovalent interactions, highly ordered structures, and multifunctional properties. Yet, the fundamental understanding of their “structure–property relationship” remains very challenging. Herein, two kinetically controlled supramolecular charge transfer (CT) complexes were conceptualized from a trimorphic molecular donor denoted as “twisted aromatic hydrocarbon” (TAH), with p-fluoranil (TFQ) and p-chloranil (TCQ) in water, organic solvent, and solvent-free methods. Elucidating their co-assembling mechanism revealed that segmentation of the TAH with molecules having planar deficient cores spontaneously formed a distinct “H-type mixed stack” and “J-type segregated stack”, regulated by blue/red-shifted charge-transfer and π-π stacking including weak C-H···F and C-H···O noncovalent interactions. By utilizing the structural transformational ability of the self-assembled TAH, the mechanistic aspects for the rapid nanoscopic co-assembly formation were precisely demonstrated experimentally and theoretically. The trimorphs and co-crystals of TAH could be disassembled resulting in turn-on emission by applying various external stimuli and being repeatedly reconfigured, thus providing a unique structure–property relationship and new TAH-based materials. This unique concept offers color-specific polymorphism and CT-complex formation strategy involving a simple class of functional materials having cooperative network forming ability using the twisted molecular donor.

Highly efficient color-tunable organic co-crystals unveiling polymorphism, isomerism, delayed fluorescence for optical waveguides and cell-imaging

“…Previous report on the solid and aggregated state photophysical and morphological properties of TAH donor molecule (Supplementary Fig. 29 ) 42 , provided key evidence to initiate investigations on the aggregation behavior of the afforded TAH co-crystals. Hence, initially, AIE behavior was studied using various fractions of THF/water mixtures.…”

Review on recent trends and prospects in π‐conjugated luminescent aggregates for biomedical applications

“…[58,59] Since the first Nobel Prize on supramolecules was awarded to Pedersen, Cram, and Lehn in 1987, several supramolecular systems were established encompassing guest-host materials, metallacycles, hydrogels, and so on, regulated by weak noncovalent interactions. [60] Among all the noncovalent interactions, π-π interaction is one of the intriguing factors that plays a pivotal role to generate supramolecules with advanced luminescent properties (Figure 1C). However, this interaction became a curse to planar organic molecules due to the notorious ACQ phenomena until the coining of AIE in 2001.…”

Exceptional class of thermally activated delayed fluorescent emitters that display pure blue, near-IR, circularly polarized luminescence and multifunctional behaviour for highly efficient and stable OLEDs

“…73,74 The most common approach to realizing this type of combined multi- This journal is © The Royal Society of Chemistry 2022 functionality was found to be via an orthogonally linked donor (D) and electron-deficient acceptor (A) system with specific molecular arrangements. 75,76 Multifunctional white-emitting TADF compounds are potential candidates for efficient and multi-responsive photoelectric devices. Molecular heredity is the most convenient approach for such materials, to avoid complex molecular design strategies.…”

“…73,74 The most common approach to realizing this type of combined multi-functionality was found to be via an orthogonally linked donor (D) and electron-deficient acceptor (A) system with specific molecular arrangements. 75,76…”