[2]Pseudorotaxanes based on the cryptand/monopyridinium recognition motif

The first cryptand/monopyridinium [2]pseudorotaxanes were prepared from five bis(m-phenylene)-32-crown-10- and one bis(m-phenylene)-26-crown-8-based cryptand hosts and three monopyridinium guests. These pseudorotaxanes were studied by proton NMR spectroscopy, mass spectrometry, and X-ray crystallography. Association constants ranged from 141 M⁻¹ to 1.86×10⁴ M⁻¹ in 1:1 acetone: chloroform at 22 °C.     

[3]Pseudorotaxanes based on the cryptand/monopyridinium salt recognition motif

The first cryptand/monopyridinium salt [3]pseudorotaxanes were prepared from two cryptand hosts and two bispyridinium guests as confirmed by proton NMR characterization, electrospray ionization mass spectrometry, and X-ray analysis. It was found that the two monopyridinium binding sites are independent of each other for the formation of one [3]pseudorotaxane.     

Two protocols for the preparation of [2]rotaxanes based on the dibenzo-24-crown-8-based cryptand/paraquat recognition motif

Host–guest complexation between a dibenzo-24-crown-8-based cryptand and a paraquat derivative was studied. Subsequently, two novel [2]rotaxanes based on the dibenzo-24-crown-8-based cryptand/paraquat recognition motif were prepared by threading-followed-by-stoppering method and single-pot method, respectively. The obtained mechanically interlocked structures were confirmed by ¹H NMR, ¹³C NMR, 2D NMR, and ESI-MS.     

Slow-exchange C3-symmetric cryptand/trispyridinium inclusion complexes containing non-linear guests: a new type of threaded structure

Slow-exchange C₃-symmetric inclusion complexes were successfully prepared based on a new cryptand/trispyridinium recognition motif as confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and molecular modeling. These inclusion complexes are the first examples of a new type of threaded structure with non-linear guests.     

Preparation of two new [2]rotaxanes based on the pillar[5]arene/alkane recognition motif

Based on the pillar[5]arene/alkane recognition motif, two [2]rotaxanes were successfully prepared. Their formation was confirmed by NMR spectroscopy and ESI mass spectrometry. We also demonstrated that 3,5-dinitrophenyl group and 3,5-bis(trifluoromethyl)phenyl group are big enough to work as stoppers for DPPillar[5]arene, which lays a foundation for the preparation of more complex and functional supramolecular structures.     

Novel [2]rotaxanes based on the recognition of pillar[5]arenes to an alkane functionalized with triazole moieties

Host-guest complexation between an alkane functionalized with triazole moieties and three pillar[5]arenes was studied. Three pillar[5]arene-based [2]rotaxanes were constructed based on this new recognition motif. The sequence of the yields of these [2]rotaxanes was consistent with the order of association constants between the three corresponding pillar[5]arenes and the alkane. ¹H NMR, electrospray ionization mass spectrometry, and NOESY NMR were employed to characterize these [2]rotaxanes.     

Efficient syntheses of bis(m-phenylene)-26-crown-8-based cryptand/paraquat derivative [2]rotaxanes by immediate solvent evaporation method

A novel bis(m-phenylene)-26-crown-8-based cryptand has been synthesized. It has been used to prepare two 1:1 complexes with two paraquat derivatives with high association constants (6.5×10⁵ and 4.0×10⁵ M⁻¹) in acetone. In the solid state the cryptand forms a 2:1 threaded structure with paraquat and an interesting supramolecular poly[2]pseudorotaxane threaded structure with a dihydroxyethyl-substituted paraquat derivative, respectively. It has been further used to prepare cryptand/paraquat derivative [2]rotaxanes efficiently by the immediate solvent evaporation method using easily available 3,5-dimethylphenyl groups as the stoppers.     

Bis(m-phenylene)-32-crown-10/monopyridinium [2]pseudorotaxanes

The first crown ether/monopyridinium threaded structures, which are [2]pseudorotaxanes based on a new bis(m-phenylene)-32-crown-10/monopyridinium recognition motif, were successfully prepared as confirmed by proton NMR spectroscopy, electrospray ionization mass spectrometry, and X-ray analysis.     

Bis(meta-phenylene)-32-crown-10-based cryptand/diquat inclusion [2]complexes

Bis(meta-phenylene)-32-crown-10-based cryptands have been proved to complex diquat much more strongly than bis(meta-phenylene)-32-crown-10 itself; in fact, one containing a pyridyl moiety has one of the highest Ka values yet reported.     

Host size effect in the complexation of two bis(m-phenylene)-32-crown-10-based cryptands with a diazapyrenium salt

N,N′-Dimethyl-2,7-diazapyrenium bis(hexafluorophosphate) binds a C₃-symmetric bis(m-phenylene)-32-crown-10-based cryptand more strongly than N,N′-dimethyl-4,4′-bipyridinium bis(hexafluorophosphate) partly because of its better fit in size with the cryptand host cavity, while it binds a relatively smaller pyridyl cryptand less strongly due to its worse fit in size with the cryptand host cavity and the lack of hydrogen bonding to the pyridyl nitrogen atom of the host.     

High-yield preparation of [2]rotaxanes based on the bis(m-phenylene)-32-crown-10-based cryptand/paraquat derivative recognition motif

Based on the complexation between bis(m-phenylene)-32-crown-10-based cryptands and a paraquat derivative, two [2]rotaxanes were synthesized by using a threading-followed-by-stoppering method. Due to the strong associations between the cryptands and the paraquat derivative, high yields were achieved even in dilute solution.     

Supramolecular photoswitch with white-light emission based on bridged bis(pillar[5]arene)s

White light-emitting (WLE) switches have greatly promising and worthy applications in the field of controllable lighting, display, and sensing. Here, we unprecedentedly construct a photocontrollable light-harvesting supramolecular nanoassembly (G/H@NiR) with rarely switchable white light emission, which comprised oligo(phenylenevinylene)-bridged pillar[5]arenes (H), photochromic diarylethene (G), and Nile red (NiR), through host–guest complexation. In the nanosystem, color-tunable photoluminescence such as cyan, orange red, and especially white with chromaticity coordinates (0.33, 0.34) is achieved through altering the proportions of the energy donor (H in assembly G/H) and acceptor center (NiR). Importantly, G, acting as a modulator, can controllably change the energy-transfer (ET) pathway between H and NiR, when the G/H@NiR nanoassembly was exposed to distinct light, achieving reversible switching of multicolor photoluminescence including white-light emission. In addition, the designed intelligent supramolecular assembly G/H@NiR with captivating characteristics has extremely valuable application as erasable multicolor fluorescent inks to be filled in the groove of a three-dimensional model and further form a high-security-level chromatic anticounterfeiting quick response (QR) code, which can be completely hidden and revealed under stimulation of distinct light. Besides, the erasable fluorescent inks can also be used to record data information in mixed fiber film, which can be completely wiped off and rerecord by distinct light. The study provides a controllable supramolecular light-harvesting strategy (the photo-modulating ET pathway in the light-harvesting process) for developing photo-responsive intelligent photoluminescence materials, particularly photosensitive WLE materials, possessing potential applications in photosensitive lighting and display, multicolor imaging, light-manipulative data storage, and high-security-level anticounterfeiting.     

柱芳烃的合成及主客体化学研究进展

柱芳烃是由对苯二酚或对苯二酚醚通过亚甲基桥在苯环的对位连接而成的一类环状低聚物, 是一类新型的大环主体分子. 本文介绍了柱芳烃和功能化柱芳烃分子的合成, 以及在分子识别、 自组装等主客体化学方面的最新研究进展, 并对其研究前景进行展望.     

Detection of cationic guest molecules by quenching of luminescence of a self-assembled host molecule consisting of terbium(III) and calix[4]arene-p-tetrasulfonates

By self-assembly in aqueous solution, calix- (CAS) and thiacalix[4]arene-p-tetrasulfonate (TCAS) formed luminescent complexes Tb^III·(CAS)₂ and Tb^III·TCAS, respectively, which were utilized as a host for cationic guests. Addition of 1-ethylpyridinium guest quenched luminescence of Tb^III·(CAS)₂ in accordance with the Stern-Volmer (SV) relation with a low detection limit (D.L.) of 5.94 × 10⁻⁸ M (S/N = 3, M ≡ mol dm⁻³). On the other hand, 1-ethylquinolinium quenched luminescence of Tb^III·TCAS most efficiently, affording a very low D.L. (6.71 × 10⁻¹⁰ M). The agreement of the SV coefficients obtained with luminescent intensity (K_SV,all = 6.74 × 10⁶ M⁻¹) and lifetime (K_SV,Tb = 6.50 × 10⁶ M⁻¹) implied that dynamic quenching of ⁵D₄ excited state of Tb^III was predominant in the quenching processes. The quenching rate was estimated to be k_q,Tb = 9.94 × 10⁹ M⁻¹ s⁻¹, which was as fast as diffusion-limited rate. Quenching of Tb^III·(CAS)₂ was also applied to detection of NAD⁺, with a D.L. of 2.78 × 10⁻⁷ M.     

Inclusion complexation of diquat and paraquat by the hosts cucurbit[7]uril and cucurbit[8]uril

The binding interactions in aqueous solution between the dicationic guest diquat (DQ(2+)) and the cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) hosts were investigated by (1)H NMR, UV/Vis, and fluorescence spectroscopy; mass spectrometry; single-crystal X-ray diffraction; and electrochemical techniques. The binding data were compared with previously reported results for the related paraquat guest (PQ(2+)). DQ(2+) was found to bind poorly (K=350 m(-1)) inside CB7 and more effectively (K=4.8 x 10(4) m(-1)) inside CB8. One-electron reduction led to increased binding affinity with both hosts (K(r)=1 x 10(4) m(-1) with CB7 and K(r)=6 x 10(5) m(-1) for CB8). While (1)H NMR spectroscopic data revealed that DQ(2+) is not fully included by CB7, the crystal structure of the CB8DQ(2+) complex-obtained from single-crystal X-ray diffraction-clearly establishes its inclusion nature. Overall, both diquat and its one-electron reduced radical cation are bound more effectively by CB8 than by CB7. In contrast to this, paraquat exhibits selectivity for CB7, but its radical cation forms a highly stable dimer inside CB8. These differences highlight the pronounced sensitivity of cucurbit[n]uril hosts to guest features such as charge, charge distribution and shape.     

One-pot synthesis of donor-acceptor [2]rotaxanes based on cryptand-paraquat recognition motif

Two novel cryptand-based [2]rotaxanes were synthesized by a facile one-pot reaction from three neutral precursors: easily accessible cryptand host 1 and commercially available 4,4'-bipyridine and 3,5-di-tert-butylbenzyl bromide. Their structures were confirmed by (1)H NMR, 2D NMR, HRMS and X-ray analysis. Moreover, two [2]pseudorotaxanes based on the same cryptand hosts and dibenzyl viologen guest 3 were also demonstrated both in solution and in the solid state, which are different from previously reported [3]pseudorotaxane-like complexes formed by dimethyl viologen guest 2 and the cryptands.     

Direct synthesis of new cryptates based on the N,C-pyrazolylpyridine motif

An expeditious synthesis of new cryptands derived from N,C-pyrazolylpyridine and their full characterization is reported. Emission lifetimes of the europium and terbium cryptates were in the range of milliseconds and terbium quantum yield was high.     

A new cryptand/paraquat [2]pseudorotaxane

A new cryptand/paraquat [2]pseudorotaxane and its crown ether analog were synthesized and characterized by proton NMR, mass spectrometry, and single crystal X-ray analysis. The Job plots based on proton NMR data demonstrated that both the complex between cryptand 1 and paraquat derivative 2a and the complex between bis(p-phenylene)-34-crown-10 (3) and paraquat derivative 2b have 1:1 stoichiometry in solution. The apparent association constants (Ka,exp) of 1·2a and 3·2b calculated for 1:1 complexes were 1.4 ...     

Dimeric Calix[4]resorcinarene-based Porous Organic Cages for CO2/CH4 Separation

Investigating gas separation by emerging porous organic cage(POC) solids is still on its initial stage. In this work, two novel [2+4] organic cages with distinguished structures have been prepared based on the Schiff-based condensation reaction between tetraformyl-functionalized calix[4]resorcinarene building blocks and xylylenediamine(XDA) isomers. Specifically, the use of para-position XDA affords lantern-shaped cage(CPOC-105) with a medium cavity of ca. 0.526 nm³, while the meta-position produces peanut-shaped structure(CPOC-106) with two small cavities of ca. 0.181 nm³. Both CPOC-105 and CPOC-106 exhibit high selectivity capture of CO₂ over CH₄ with calculated selectivity coefficients of 4.5 and 3.1, respectively, under ambient conditions, and are capable of separating CO₂/CH₄ mixtures by fixed-bed column breakthrough experiments.     

A self-assembling metallosupramolecular cage based on cavitand-terpyridine subunits

Metal-directed self-assembly of a terpyridyl-functionalized cavitand yields a large hexameric coordination cage.