A new class of chiral macrocyclic arene composed of three chiral 2,6-dihydroxyltriptycene subunits bridged by methylene groups was designed and synthesized. Structural studies showed that the macrocyclic molecule adopts a hex-nut-like structure with a helical chiral cavity and highly fixed conformation. Efficient resolution was achieved through the introduction of chiral auxiliaries to give a couple of enantiopure macrocycles, which exhibited high enantioselectivity towards three pairs of chiral compounds containing a trimethylamino group.

A new class of chiral macrocyclic arene composed of three chiral 2,6-dihydroxyltriptycene subunits bridged by methylene groups was designed and synthesized. Structural studies showed that the macrocyclic molecule adopts a hex-nut-like structure with a helical chiral cavity and highly fixed conformation. Efficient resolution was achieved through the introduction of chiral auxiliaries to give a couple of enantiopure macrocycles, which exhibited high enantioselectivity towards three pairs of chiral compounds containing a trimethylamino group.

Complexation between a triptycene-derived macrotricyclic polyether and π-extended viologens with different linker lengths in both the solution and the solid state was investigated in detail. No changes in complexation modes were observed with the host and guests of different linker length bearing methyl terminal functional groups, whereas different complexation modes were found with the host and guests of different linker length bearing methoxyethyl terminal functional groups. It was also found that two different complexation modes could exist in the same unit cell. Furthermore, we found that the binding and release of the guest in the complex could easily be controlled by addition and removal of K⁺ ions.

Four new fluorescent dyes containing tetrahydro[5]helicene moiety characterized by three-primary emission colors (blue-green-red) are designed and synthesized, and their structures are characterized by NMR, MS, and single crystal X-ray crystallography. Organic nanoparticles based on the fluorescent dyes are then prepared by re-precipitation method, and their photophysical properties are investigated. These nanoparticles retain the strong emissions of the organic dyes, and multicolor nanoparticles were also prepared by simply tuning the ratios of the three-primary colors dyes. These organic nanoparticles exhibit low cytotoxicity, good photostability, and high quantum yields. Moreover, the nanoparticles can also be applied in the cell fluorescence imaging. Especially, it is interestingly found that the stained regions of these nanoparticles from membrane to cytoplasm for HeLa cells show obvious structure-dependent properties. This strategy provides a new perspective to fluorescence probe by molecular design for specific location imaging of living cells.

Triptycene-derived p-dibromocalix[5]arene was synthesized by a fragment-coupling approach, whereas treatment of the triptycene-derived calix[5]arene containing three p-tert-butyl phenol groups and a 1,8-dimethoxytriptycene moiety with excess bromine in dichloromethane at room temperature produced triptycene-derived p-pentabromocalix[5]arene directly. Methyl etherification and Suzuki coupling reactions were then carried out. As a result, a series of triptycene-derived calix[5]arene derivatives in fixed cone and 1,2-alternate conformations were obtained. Moreover, conformation transformations of triptycene-derived calix[5]arenes from cone to 1,2-alternate forms could also be achieved.

A triptycene-derived macrotricyclic host containing two pyridine groups was synthesized, and it could form 1:1 stable host-guest complexes with paraquat derivatives in both solution and solid state. Moreover, it was also found that binding and releasing of the guest molecules in the complexes could be efficiently controlled by zinc ions.

Oxidative dearomatization is a powerful strategy in organic synthesis. However, reports on using dioxygen as the oxidant, as it is environmentally friendly, readily available (air), and easy to handle, are rather limited. Helicene diols can undergo transannular dearomatization triggered by dioxygen to give diones in quantitative yields within several minutes. By virtue of this, the chirality is successfully transferred from helicity to central chirality to form distorted π-extended diones having two all-carbon quaternary stereocenters. The optical resolution was achieved by column chromatography, and the structures and the absolute configurations of the chiral diones were determined by X-ray analysis.

Oxidative dearomatization is a powerful strategy in organic synthesis. However, reports on using dioxygen as the oxidant, as it is environmentally friendly, readily available (air), and easy to handle, are rather limited. Helicene diols can undergo transannular dearomatization triggered by dioxygen to give diones in quantitative yields within several minutes. By virtue of this, the chirality is successfully transferred from helicity to central chirality to form distorted π-extended diones having two all-carbon quaternary stereocenters. The optical resolution was achieved by column chromatography, and the structures and the absolute configurations of the chiral diones were determined by X-ray analysis.

A series of aza[4]helicenes have been conveniently synthesized in yields of 71–92 % by a one-pot procedure involving the Pictet–Spengler reaction. The structures of the aza[4]helicenes were characterized by ¹H and ¹³C NMR spectroscopy, mass spectrometry, and X-ray crystallography. Moreover, it was found that the aza[4]helicenes self-assemble into 2D layers or herringbone-like structures in the solid state. In addition, the optical properties were investigated by UV and fluorescence spectroscopic methods.

Triptycene-derived cylindrical macrotricyclic host with two dibenzo-30-crown-10 cavities could form stable 1:1 complexes with not only polyether linked bisparaquat derivative but also a self-folding A-D-A guest in solution and/or solid state. Moreover, it was found that switchable processes between the host and both the bisparaquat derivative and the self-folding guest could be further controlled by potassium ions.

Iptycenes are a class of aromatic compounds with arene units fused to the [2.2.2]bicyclooctatriene bridgehead system. As a result of their unique structures, more and more iptycenes, especially triptycene and pentiptycene derivatives, have been efficiently synthesized. These compounds have wide applications in many research areas, including molecular machines, molecular balances, catalysis, materials chemistry, molecular assembly, host–guest chemistry, and so on. This microreview mainly describes the developments in the synthesis and applications of triptycene and pentiptycene derivatives during the last ten years. Particular attention is paid to the synthesis and applications of hosts derived from triptycene and pentiptycene systems in recent years.

A series of benzo[1,2-f:5,4-f′]diquinoline derivatives were synthesized starting from 2,7-diaminoanthracene, and their structures were determined by NMR, MS spectra and X-ray analysis. They showed a remarkably strong intramolecular CH···O hydrogen bond, which resulted in an unexpected downfield chemical shift of the aromatic proton in CDCl₃. Moreover, a significant fluorescent change of molecule 1b in the presence of trifluoroacetic acid (TFA) was also observed.

A pair of triptycene-derived oxacalixarenes, 1 a and 1 b, containing two naphthyridine subunits have been synthesized by a convenient one-pot approach. Macrocycles 1 a and 1 b are diastereomers, with 1 a being a cis isomer with a boat-like 1,3-alternate conformation and 1 b being a trans isomer with a curved boat-like conformation in the solid state. Both 1 a and 1 b have fixed conformations in solution at room temperature, as revealed by variable-temperature ¹H NMR spectroscopy experiments. It was found that oxacalixarenes 1 a and 1 b could both form 1:1 [2]pseudorotaxane-type complexes with paraquat derivatives with different functional groups in solution and in the solid state, which resulted in the further synthesis of a pair of novel isomeric [2]rotaxanes. Moreover, the controlled dethreading and rethreading processes of the [2]pseudorotaxanes were also easily achieved by acid–base stimuli or Hg²⁺ association/dissociation.

Self-complementary monomer 1, which combines a macrotricyclic polyether and two dibenzylammonium ions together, was synthesized, and its self-assembly into supramolecular polymer networks by host–guest interactions was studied. For the purpose of comparative study, two model molecules 2 and 3 were also prepared. It was found that model molecule 2 and dibenzylammonium ion 4 form a 1:2 complex in solution and in the solid state, which afforded a model system for the investigation of the assembly behavior of monomer 1. Consequently, the ¹H NMR spectrum of 1 in CD₃CN showed characteristic proton signals similar to the model system, which suggested that 1 self-assembles into a supramolecular polymer network. Formation of the supramolecular polymer was further evidenced by the MALDI-TOF MS spectrum, viscometry, and dynamic light-scattering (DLS) experiments. Moreover, it was found that the decomposition and re-formation of the supramolecular polymer could be chemically controlled by the use of triethylamine and trifluoroacetic acid. Interestingly, the supramolecular polymer forms an organogel both in CD₃CN and in 1:1 (v/v) CDCl₃/CD₃CN, and reversible thermo- and pH-induced gel–sol transitions were also found. The presented work will provide a new strategy for the construction of supramolecular polymers with specific structures and properties.

A novel triptycene-derived bis-macrotricyclic host was designed and synthesized. The host was shown to form a 1:4 stable complex with 4 equiv. of dibenzylammonium salt in solution and in the solid state. Moreover, it was found that the host with multicavities could also self-assemble with 2 equiv. of bis-secondary ammonium salt to form a handcuff-like structure under the tested condition ([1]₀ = 3.0 mM). The complexation and decomplexation of the assembly could be further chemically controlled by the stimuli of acid and base.

A new fluorescent chemosensor based on an open-chain azacrown bearing a quinoline subunit was conveniently synthesized, which showed a remarkable enhanced fluorescent intensity in the presence of Cu²⁺ ion and a high selectivity toward Cu²⁺ ion over a wide range of tested metal ions in acetonitrile.

On the basis of formation of [2]pseudorotaxane complexes between triptycene-derived tetralactam macrocycles 1 a and 1 b and squaraine dyes, construction of squaraine-based [2]rotaxanes through clipping reactions were studied in detail. As a result, when two symmetrical squaraines 2 d and 2 e were utilized as templates, two pairs of isomeric [2]rotaxanes 3 a–b and 4 a–b as diastereomers were obtained, owing to the two possible linking modes of triptycene derivatives. It was also found, interestingly, that when a nonsymmetrical dye 2 g was involved, there existed simultaneously three isomers of [2]rotaxanes in one reaction due to the different directions of the guest threading. The ¹H NMR and 2D NOESY NMR spectra were used to distinguish the isomers, and the yield of [2]rotaxane 5 a with the benzyl group in the wider rim of the host 1 a was found to be higher than that of another isomer 5 b with an opposite direction of the guest, which indicated the partial selection of the threading direction. The X-ray structures of 3 b and 4 a showed that, except for the standard hydrogen bonds between the amide protons of the hosts and the carbonyl oxygen atoms of the guests, multiple π⋅⋅⋅π stacking and CH⋅⋅⋅π interactions between triptycene subunits and aromatic rings of the guests also participated in the complexation. Crystallographic studies also revealed that the [2]rotaxane molecules 3 b and 4 a further self-assembled into tubular structures in the solid state with the squaraine dyes inside the channels. In the case of 4 a, all the nonsymmetrical macrocyclic molecules pointed in one direction, which suggests the formation of oriented tubular structures. Moreover, it was also found that the squaraines encapsulated in the triptycene-derived macrocycles were protected from chemical attack, and subsequently have potential applications in imaging probes and other biomedical areas.

Two pairs of novel triptycene-derived calix[6]arenes 4 a,b and 5 a,b have been efficiently synthesized through both one-pot and two-step fragment-coupling strategies starting from 2,7-bis(hydroxymethyl)-1,8-dimethoxytriptycene 1. Subsequent demethylation of 4 a,b and 5 a,b with BBr₃ in dry dichloromethane gave the macrocyclic compounds 6 a,b and 7 a,b. Treatment of either 4 a or 6 a with AlCl₃ resulted in the same debutylated product 8, while 9 was similarly obtained from either 5 a or 7 a. Structural studies revealed that all of the macrocycles have well-defined structures with fixed conformations both in solution and in the solid state owing to the introduction of the triptycene moiety with a rigid three-dimensional (3D) structure, making them very different from their classical calix[6]arene counterparts. As a consequence, it was found that all of these the triptycene-derived calix[6]arenes could encapsulate small neutral molecules in their cavities in the solid state. Moreover, it was also found that the macrocycles 4 b and 5 b showed highly efficient complexation abilities toward fullerenes C₆₀ and C₇₀, forming 1:1 complexes with association constants ranging from (5.22±0.20)×10⁴ to (8.68±0.30)×10⁴ M⁻¹.

A new calix[4]arene-based fluorescent chemosensor bearing four dansyl amides on the upper rim (1) was conveniently synthesized, which showed high sensitivity and selectivity toward Hg²⁺ over a wide range of metal ions in 50% aqueous acetonitrile. The complexation of Hg²⁺ ion induced a strong fluorescence quenching of 1 due to a well-defined electron transfer process from the dansyl group(s) to the metal center. Compared with compounds 2 and 3, tetradansyl amide substituted calix[4]arene 1 showed a preorganized and coordinated complexing site for metal ions. Moreover, the detection limit for Hg²⁺ was found to be 3.41×10⁻⁶ mol·L⁻¹, which might make 1 a potentially practical Hg²⁺-selective fluorescent sensor in aqueous system.