A general supramolecular strategy for fabricating full-color-tunable thermally activated delayed fluorescence materials.

Developing a facile and feasible strategy to fabricate thermally activated delayed fluorescence materials exhibiting full-color tunability remains an appealing yet challenging task. In this work, a general supramolecular strategy for fabricating thermally activated delayed fluorescence materials is proposed. Consequently, a series of host-guest cocrystals are prepared by electron-donating calix[3]acridan and various electron-withdrawing guests. Owing to the through-space charge transfer mediated by multiple noncovalent interactions, these cocrystals all display efficient thermally activated delayed fluorescence. Especially, by delicately modulating the electron-withdrawing ability of the guest molecules, the emission colors of these cocrystals can be continuously tuned from blue (440 nm) to red (610 nm). Meanwhile, high photoluminescence quantum yields of up to 87% is achieved. This research not only provides an alternative and general strategy for the fabrication of thermally activated delayed fluorescence materials, but also establishes a reliable supramolecular protocol toward the design of advanced luminescent materials.

A novel thermally activated delayed fluorescence macrocycle.

A novel luminescent macrocycle has been conveniently synthesized, which displays flexible conformations and interesting solid-state host-guest properties. Besides, the macrocycle exhibits excellent thermally activated delayed fluorescence (TADF) emission with a photoluminescence quantum yield of 80%, which represents the highest value among reported TADF macrocycles.

Adsorptive separation of picoline isomers by adaptive calix[3]acridan crystals.

The exploration of macrocycle-based nonporous adaptive crystals (NACs) for adsorption and separation has been one of the hotspots in supramolecular chemistry and crystal engineering. Herein, we developed calix[3]acridan-based NACs to separate industrially important 4-picoline from its isomer mixtures with over 93.8% purity.

A Calix[3]acridan-Based Host-Guest Cocrystal Exhibiting Efficient Thermally Activated Delayed Fluorescence.

A supramolecular strategy to construct thermally activated delayed fluorescence (TADF) materials through host-guest charge transfer interactions was proposed. Consequently, a new class of macrocycle namely calix[3]acridan was conveniently synthesized in 90 % yield. The host-guest cocrystal formed by calix[3]acridan and 1,2-dicyanobenzene exhibited efficient TADF properties due to intense intermolecular charge transfer interactions. Moreover, the spatially separated highest occupied molecular orbital and lowest unoccupied molecular orbital resulted in a very small singlet-triplet energy gap of 0.014 eV and hence guaranteed an efficient reverse intersystem crossing for TADF. Especially, a high photoluminescence quantum yield of 70 % was achieved, and it represents the highest value among the reported intermolecular donor-acceptor TADF materials.

Chiral TADF-Active Polymers for High-Efficiency Circularly Polarized Organic Light-Emitting Diodes.

A strategy of chiral donor-acceptor copolymerization is proposed to develop chiral nonconjugated polymers with thermally activated delayed fluorescence (TADF). Based on this strategy, two pairs of chiral polymers (R,R)-/(S,S)-pTpAcDPS and (R,R)-/(S,S)-pTpAcBP were synthesized. The alternating copolymerization of the chiral donors and acceptors could effectively separate the frontier molecular orbitals, which made the polymers show small ΔEST of 0.01-0.03 eV and efficient TADF properties. Moreover, the polymers also showed the quantum yield of up to 92 % and the circularly polarized luminescence. The solution-processed circularly polarized organic light-emitting diodes showed circularly polarized electroluminescence signals with high external quantum efficiencies of up to 22.1 % and maximum luminance of up to 34350 cd m-2 . This is the first report of CP-OLEDs based on chiral TADF polymer, which provides a useful and valuable guidance for the development of high-efficiency CPEL polymers.

Saucer[n]arenes: Synthesis, Structure, Complexation, and Guest-Induced Circularly Polarized Luminescence Property.

Macrocycles denoted as saucer[n]arenes (n=4,5) were easily synthesized by the one-pot condensation of 2,7-dimethoxynaphthalene (2,7-DMN) and paraformaldehyde in the presence of TFA or catalytic BF3 ⋅OEt2 . With 1,1-dimethylpiperidin-1-ium as the template, saucer[4]arene was selectively obtained. Crystal structures show that saucer[n]arenes are all composed of 2,7-DMN moiety bridged by the methylene groups at 1,6-positions: all of the 7-methoxy groups lie on one face, and all of the 2-methoxy groups lie on the other. Saucer[n]arenes exhibit strong fluorescence properties with the quantum yields of 19.6 % and 23.4 %. They form 1:1 complexes with ammonium salts in both solution and solid state (association constant up to 105  M-1 in CDCl3 ). Chiral quaternary ammonium salts can induce the chirality of the dynamically racemic inherently chiral saucer[n]arenes in solution, and thus show mirror-imaged circular dichroism signals and circularly polarized luminescence (CPL) properties.

Helic[1]triptycene[3]arene: Synthesis, Complexation, and Formation of [2]Rotaxane Shuttle.

A new macrocyclic arene, helic[1]triptycene[3]arene H, was conveniently synthesized in 37% yield by a one-pot reaction starting from 2,6-dimethoxyl-3,7-dihydroxymethyltriptycene. Macrocycle H showed fixed conformation in solution and could form 1:1 complexes with a series of neutral guests, secondary ammonium salts, and tertiary ammonium salts in both solution and solid states. The association constants between H and the neutral guests were between (1.23 ± 0.10) × 102 and (4.70 ± 0.47) × 103 M-1, while the association constants between H and the ammonium guests were between (1.35 ± 0.12) × 103 and (1.59 ± 0.14) × 105 M-1. Moreover, H showed bigger association constants with secondary ammonium salts than those with tertiary ammonium salts possibly because of the steric hindrance effect and multiple intermolecular interactions. The stimuli-responsive complexation between H and the ammonium salts could be controlled by the addition and removal of acids and bases as well. Based on the host-guest complexation between H and the secondary ammonium salt, [2]rotaxane was further synthesized, and its shuttling motion could be efficiently controlled by an acid and base.

Recent advances in higher order rotaxane architectures.

Despite dramatic advances in the template-directed synthesis of archetypal [2]rotaxanes, higher order rotaxanes with multiple molecular components (rings or dumbbells) are relatively daunting subjects owing to their synthetic challenges. With unique interlocked architectures, higher order rotaxanes have found applications in artificial molecular machines. In this feature article, we will focus on the recent advances in higher order rotaxanes with well-defined structures. Different types of rotaxane architectures will be described, and their synthetic approaches will be highlighted. Moreover, the stimuli-responsive molecular motion with increasing complexity in these diverse architectures will also be discussed.

Directional Transportation of a Helic[6]arene along a Nonsymmetric Molecular Axle.

Directional transportation of a helic[6]arene along a nonsymmetric molecular axle was achieved, which was easily performed in dichloromethane by a stopper reaction and subsequent addition of fluoride ions. In this system, the fluoride ions could act as a versatile stimulus to unidirectionally release the macrocycle that not only destroyed the host-guest interaction but also removed the silyl stopper.