Applying the B/N Lewis Pair Approach to Access Fusion-Expanded Binaphthyl-Based Chiral Analogues.

We herein describe the synthesis of two axially chiral systems (HBN and BBN) by the incorporation of B centers into binaphthyl derivatives (HPy and BPy). Heteroatom-doped chiral polycyclic aromatic hydrocarbons were thus formed by fusion of the azaboroles to binaphthyls with the formation of B-N dative bonds. The resulting B-N Lewis pairs that serve as attractive fluorophores enabled modulation of the chiroptical properties both in solution and in the solid state.

Pillar[5]arene-Based Dual Chiral Organoboranes with Allowed Host-Guest Chemistry and Circularly Polarized Luminescence.

We first describe two examples of highly luminescent organoboranes (NP5BN1 and NP5BN2) with dual chirality that were achieved by molecular functionalization of planar chiral pillar[5]arenes with naphthyls. Sufficiently strong steric effects are imposed by triarylamine (Ar3N) and triarylborane (Ar3B) moieties and further enhanced by the proximity of the chiral building blocks, leading to the isolation of multiple enantiomers via chiral high-performance liquid chromatography. The intramolecular charge transfer from N-donor to B-acceptor across both chiral subunits enabled the circularly polarized luminescence and thermally robust colorimetric responses in their emissions. Furthermore, their remarkable host-guest chemistry was allowed at no expense in the pursuit of advanced chiroptical properties using pillar[5]arene-based supramolecular scaffolds.

Planar Chiral Organoboranes with Thermoresponsive Emission and Circularly Polarized Luminescence: Integration of Pillar[5]arenes with Boron Chemistry.

Enantiopure molecules based on macrocyclic architecture are unique for applications in enantioselective host-guest recognition, chiral sensing and asymmetric catalysis. Taking advantage of the chiral transfer from the intrinsically planar chirality of pillar[5]arenes, we herein present an efficient and straightforward approach to achieve early examples of highly luminescent chiral systems (P5NN and P5BN). The optical resolution of their enantiomers has been carried out via preparative chiral HPLC, which was ascribed to the molecular functionalization of pillar[5]arenes with π-conjugated, sterically bulky triarylamine (Ar3 N) as an electron donor and triarylborane (Ar3 B) as an acceptor. This crucial design enabled investigations of the chiroptical properties, including circular dichroism (CD) and circularly polarized luminescence (CPL) in the solid state. The intramolecular charge transfer (ICT) nature in P5BN afforded an interesting thermochromic shift of the emission over a wide temperature range.

A novel supramolecular organogel based on acylhydrazone functionalized pillar[5]arene acts as an I- responsive smart material.

A novel organic gelator (PZ) has been synthesized by rationally connecting a pillar[5]arene moiety and a bis(hexadecyloxy)phenyl functionalized acylhydrazone moiety. PZ could self-assemble into a supramolecular polymer and form a stable organogel (OPZ) in cyclohexanol by multi-self-assembly driving forces such as C-Hπ, ππ, vdW and hydrogen bonding interactions. The organogel (OPZ) shows blue aggregation-induced emission (AIE). Interestingly, the organogel OPZ could sense iodide ions (I-) in the gel-gel state with high selectivity and sensitivity. The detection limit of OPZ for I- is 9.4 × 10-8 M, indicating high sensitivity to I-. Furthermore, a thin film based on OPZ was prepared, which could be used as a smart material for the detection of I- as well as a fluorescent security display material.

A pillar[5]arene-based multiple-stimuli responsive metal-organic gel was constructed for facile removal of mercury ions.

A thioacetohydrazide functionalized pillar[5]arene was synthesized, which could further assemble into a linear supramolecular metal-organic polymer upon adding Zn2+. Furthermore, the obtained linear supramolecular metal-organic polymer could self-assemble to form a fluorescent supramolecular metal-organic gel at high concentration. When TBAOH was added to the viscous solution at high temperature, the obtained solution could not form a supramolecular metal-organic gel upon cooling. More importantly, when Hg2+ ions are added to the metal-organic gel, the strong blue fluorescence is clearly quenched, and this metal-organic gel (xerogel) could effectively remove Hg2+ from water. Simultaneously, a thin film based on the metal-organic gel was prepared, which was confirmed to be a convenient test kit for detecting Hg2+.

Recent advances in circularly polarized luminescence of planar chiral organic compounds.

Circularly polarized luminescence (CPL), as an important chiroptical phenomenon, can not only directly characterize excited-state structural information about chiroptical materials but also has great application prospects in 3D optical displays, information storage, biological probes, CPL lasers and so forth. Recently, chiral organic small molecules with CPL have attracted a lot of research interest because of their excellent luminescence efficiency, clear molecular structures, unique flexibility and easy functionalization. Planar chiral organic compounds make up an important class of chiral organic small molecular materials and often have rigid macrocyclic skeletons, which have important research value in the field of chiral supramolecular chemistry (e.g., chiral self-assembly and chiral host-guest chemistry). Therefore, research into planar chiral organic compounds has become a hotspot for CPL. It is time to summarize the recent developments in CPL-active compounds based on planar chirality. In this feature article, we summarize various types of CPL-active compounds based on planar chirality. Meanwhile, we overview recent research in the field of planar chiral CPL-active compounds in terms of optoelectronic devices, asymmetric catalysis, and chiroptical sensing. Finally, we discuss their future research prospects in the field of CPL-active materials. We hope that this review will be helpful to research work related to planar chiral luminescent materials and promote the development of chiral macrocyclic chemistry.

A pillar[5]arene-based planar chiral charge-transfer dye with enhanced circularly polarized luminescence and multiple responsive chiroptical changes.

The fabrication of circularly polarized luminescent (CPL) organic dyes based on macrocyclic architecture has become an importantly studied topic in recent years because it is of great importance to both chiral science and supramolecular chemistry, where pillar[n]arenes are emerging as a promising class of planar chiral macrocyclic hosts for CPL. We herein synthesized an unusual planar chiral charge-transfer dye (P5BB) by covalent coupling of triarylborane (Ar3B) as an electron acceptor to parent pillar[5]arene as an electron donor. The intramolecular charge transfer (ICT) nature of P5BB not only caused a thermally responsive emission but also boosted the luminescence dissymmetry factor (g lum). Interestingly, the specific binding of fluoride ions changed the photophysical properties of P5BB, including absorption, fluorescence, circular dichroism (CD), and CPL, which could be exploited as an optical probe for multi-channel detection of fluoride ions. Furthermore, the chiroptical changes were observed upon addition of 1,4-dibromobutane as an achiral guest.

Pillar[5]arene-based Neutral Radicals with Doublet Red Emissions and Stable Chiroptical Properties.

Stable organic radicals with unique luminescence show great importance in photoelectromagnetic materials. We herein report two unusual radical-based systems (P5N-TTM and P5B-TTM) using the concerted effects of planar chiral pillar[5]arenes and tris(2,4,6-trichlorophenyl)methyl (TTM) radicals. The steric effect and electronic doublet-spin character of these radicals allowed the optical resolution and the first red emissions (∼650 nm) for pillar[5]arene derivatives. Notably, cross-coupling with macrocyclic pillar[5]arene, in turn, considerably enhanced the configurational stability of TTM radicals.

Pillararenes: fascinating planar chiral macrocyclic arenes.

Chiral macrocycles possess significant value in chiral science and supramolecular chemistry. Pillararenes, as a class of relatively young supramolecular macrocyclic hosts, have been widely used for host-guest recognition and self-assembly. Since the position of substituents on the benzene rings breaks the molecular symmetry (symmetric plane and symmetric center), pillararenes possess planar chirality. However, it is a great challenge to synthesize stable and resolvable enantiomers because of the easy rotation of the phenylene group. In this review, we summarize the construction methods of resolvable chiral pillararenes. We also focus on their applications in enantioselective recognition, chiral switches, chirality sensing, asymmetric catalysis, circularly polarized luminescence, metal-organic frameworks, and highly permeable membranes. Finally, we discuss the future research perspectives in this field of pillararene-based planar chiral materials. We hope that this review will encourage more researchers to work in this exciting field.

Pillararene-based fluorescent chemosensors: recent advances and perspectives.

In 2008, a new class of pillar-shaped supramolecular macrocyclic hosts was reported, known as "pillararenes". Their particular electron-rich cavity and the ease of their functionalization offer possibilities for the design and synthesis of novel fluorescent chemosensors. Subsequently, pillararene-based fluorescent sensors and probes have been rapidly developed. This feature article covers the most recent contributions from the pillararene-based fluorescent sensor field in terms of anion/cation sensing, small molecule recognition, biomolecule detection, fluorescent supramolecular aggregates, and biomedical imaging. Meanwhile, we hope that this feature article will inspire more effort to be devoted to this emerging field.

[Clinical observation on insomnia treated with multivariate acupuncture of chronomedicine].

OBJECTIVE: To compare the efficacy difference between multivariate acupuncture of chronomedicine and conventional acupuncture in the treatment of insomnia. METHODS: Fifty cases were randomly divided into a multivariate acupuncture of chronomedicine group (group A) and a rountine acupuncture group (group B), 25 cases in each one. The acupoints selected were same in each group, such as Zusanli (ST 36), Sanyinjiao (SP 6), Shenmen (HT 7) and Chize (LU 5), etc. In group A, the patient was treated according to visit time. In light of the time division, the special acupoint of the on-duty meridian that qi and blood were abundant specifically was picked up at first. The other acupoints were punctured in the sequence of qi and blood flow among twelve meridians. In group B, the acupoints were punctured from up to down in terms of acupoint locations. Acupuncture was given once every two days in either group. Totally, 6 treatments were required. Pittsburgh Sleep Quality Index (PSQI) was adopted to assess PSQI total score and the score of each item before and after treatment for the patients in two groups. RESULTS: PSQI total score was reduced apparently after treatment in either group (both P < 0.05). The score in group A was lower than that in group B after treatment (7.20 +/- 2.45 vs 9.44 +/- 3.07, P < 0.05). After treatment, the improvements of the scores of sleep quality, sleep duration, sleep efficiency and sleep disturbance in group A were superior to those in group B (all P < 0.05). CONCLUSION: The multivariate acupuncture of chronomedicine improves sleep apparently for the patients with insomnia and its efficacy is better than that of conventional acupuncture.