Oligotriarylamine-Extended Organoboranes with Tunable Electron-Donating Strength by Changing the Number of Donor Units

Design and Synthesis of New Type of Macrocyclic Architectures Used for Optoelectronic Materials and Supramolecular Chemistry

Supramolecular chemistry has received much attention for decades. Macrocyclic architectures as representative receptors play a vital role in supramolecular chemistry and are applied in many fields such as supramolecular assembly and host-guest recognition. However, the classical macrocycles generally lack functional groups in the scaffolds, which limit their further applications, especially in optoelectronic materials. Therefore, developing a new design principle is not only essential to better understand macrocyclic chemistry and the supramolecular behaviors, but also further expand their applications in many research fields. In recent years, the doping compounds with main-group heteroatoms (B, N, S, O, P) into the carbon-based π-conjugated macrocycles offered a new strategy to build macrocyclic architectures with unique optoelectronic properties. In particular, the energy gaps and redox behavior can be effectively tuned by incorporating heteroatoms into the macrocyclic scaffolds. In this Minireview, we briefly summarize the design and synthesis of new macrocycles, and further discuss the related applications in optoelectronic materials and supramolecular chemistry.

Regulating donor-acceptor system toward highly efficient dual-state emission for sensitive response of nitroaromatic explosives

Dual-state emission luminogens (DSEgens) as fluorophores emit efficiently in solution and solid forms have gained increasing concern in the field of chemical sensing. Recent efforts by our group led to the identification of DSEgens as an easy-to-visualize nitroaromatic explosives (NAEs) detection platform. However, none of the previously studied NAEs probes show effective improvement in sensitivity. Here, we designed a series of benzoxazole-based DSEgens through multiple strategies driven by theoretical calculations, revealing their improved detecting performance on NAEs. Compounds 4a-4e exhibit thermal- and photo-stability, large Stokes shift as well as sensitivity solvatochromism (except for 4a and 4b). A subtle balance between rigid conjugation and distorted conformation endows these D-A type fluorophores 4a-4e with DSE properties. Furthermore, 4d and 4e show aggregation-induced emission phenomenon caused by distorted molecular conformation and restricted intramolecular rotation. Interestingly, DSEgen 4e displays anti-interference and sensitivity towards NAEs with a detection limit of 10^-8 M. It can be applied for expedient and distinct visual identification of NAEs not only in solution but also on filter paper and film, supporting this new DSEgen as reliable NAEs chemoprobe.

Expanding new chemistry of aza-boracyclophanes with unique dipolar structures, AIE and redox-active open-shell characteristics

π-Conjugated macrocycles involving electron-deficient boron species have received increasing attention due to their intriguing tunable optoelectronic properties. However, most of the reported B(sp²)-doped macrocycles are difficult to modify due to the synthetic challenge, which limits their further applications. Motivated by the research of non-strained hexameric bora- and aza-cyclophanes, we describe a new class of analogues MC-BN5 and MC-ABN5 that contain charge-reversed triarylborane (Ar₃B) units and oligomeric triarylamines (Ar₃N) in the cyclics. As predicted by DFT computations, the unique orientation of the donor-acceptor systems leads to an increased dipole moment compared with highly symmetric macrocycles (M1, M2 and M3), which was experimentally represented by a significant solvatochromic effect with large Stokes shifts up to 12 318 cm^-1. Such a ring-structured design also allows the easy peripheral modification of aza-boracyclophanes with tetraphenylethenyl (TPE) groups, giving rise to a change in the luminescence mechanism from aggregation-caused quenching (ACQ) in MC-BN5 to aggregation-induced emission (AIE) in MC-ABN5. The open-shell characteristics have been chemically enabled and were characterized by UV-Vis-NIR spectroscopy and electron paramagnetic resonance (EPR) for MC-BN5. The present study not only showed new electronic properties, but also could expand the research of B/N doped macrocycles into the future scope of supramolecular chemistry, as demonstrated in the accessible functionalization of ring systems.