Guest-dependent complexation of triptycene-based macrotricyclic host with paraquat derivatives and secondary ammonium salts: a chemically controlled complexation process

The triptycene-based macrotricyclic host containing two dibenzo-[24]-crown-8 moieties has been found to form stable 1:1 or 1:2 complexes in different complexation modes with different functional paraquat derivatives and secondary ammonium salts in solution and in the solid state. Consequently, the alkyl-substituted paraquat derivatives thread the lateral crown cavities of the host to form 1:1 complexes. It was interestingly found that the paraquat derivatives containing two beta-hydroxyethyl or gamma-hydroxypropyl groups form 1:2 complexes, in which two guests thread the central cavity of the host. Other paraquat derivatives containing terminal hydroxy, methoxy, 9-anthracylmethyl, and amide groups were included in the cavity of the host to form 1:1 complexes. Moreover, the host also forms a 1:2 complex with two 9-anthracylmethylbenzylammonium salts, in which the 9-anthracyl groups were selectively positioned outside the lateral crown cavities. The competition complexation process between the host and two different guests (the propyl-substituted paraquat derivative and a dibenzylammonium salt) could be chemically controlled.     

A triptycene-based bis(crown ether) host: complexation with both paraquat derivatives and dibenzylammonium salts

[reaction: see text] A novel triptycene-based bis(crown ether) host (1) incorporating two dibenzo-24-crown-8 ether moieties has been synthesized. It can form not only a new bis[2]pseudorotaxane with dibenzylammonium salts but also stable clip-shaped complexes with paraquat derivatives. Moreover, the complexation process between 1 and the two classes of guests can be chemically controlled.     

Synthesis of a novel triptycene-based molecular tweezer and its complexation with paraquat derivatives

[reaction: see text] A novel triptycene-based molecular tweezer has been synthesized, and its complexation with paraquat derivatives in solution and in the solid state has been studied. Due to its electron-rich cavity, the molecular tweezer could form stable complexes with paraquat derivatives with different functional groups. Moreover, it was also found that formation of the complexes was caused by a charge transfer interaction and the complexes dissociated upon two one-electron reduction of the bipyridinium ring.     

Li+-templated complexation of cylindrical macrotricyclic host with naphthalene diimide: Cation-controlled switchable complexation processes

Anthracene-based cylindrical macrotricyclic polyether (1) containing two dibenzo-30-crown-10 cavities has been proved to be an efficient host for the templated complexation with N,N’-dipropyl-1,4,5,8-naphthalenetetracarboxylic diimide in the presence of lithium ions in both solution and solid state. Host 1 could also form 1:1 complex with the bispyridinium salt with two β-hydroxyethyl groups in solution and in the solid state. Moreover, it was also found that the switchable complexation processes between the macrotricyclic host and two different kinds of guests could be chemically controlled by the addition and removal of lithium ions.     

Self-assembly of triptycene-based cylindrical macrotricyclic host with dibenzylammonium ions: construction of dendritic [3]pseudorotaxanes

[reaction: see text] It was found that a cylindrical macrotricyclic host containing two dibenzo[24]crown-8 cavities could self-assemble with two dibenzylammonium salts to form a stable 1:2 complex in solution and in the solid state, in which multiple hydrogen-bonding and pi-pi stacking interactions between the host and the guest played an important role. Furthermore, a series of dendritic pseudorotaxanes were constructed and structurally studied.     

Guest-dependent complexation of triptycene-derived macrotricyclic host containing one anthracene moiety with paraquat derivatives: construction of [2]rotaxanes

Complexation between the triptycene-derived macrotricyclic polyether containing an anthracene unit and paraquat derivatives in both solution and solid state was investigated. It was found that the macrotricyclic host with multi-cavity structure could form a series of [2]pseudorotaxanes with different terminal functionalised paraquat derivatives in different threading modes, which subsequently resulted in the construction of two novel [2]rotaxanes.     

Selective templated complexation of a cylindrical macrotricyclic host with neutral guests: three cation-controlled switchable processes

A novel triptycene-based cylindrical macrotricyclic host 1 containing an anthracene unit and two dibenzo [24]crown-8 moieties was synthesized, and its cation binding properties were studied. It was found that the host could not only form complex with the paraquat derivative 4, but also show selective templated complexation with pyromellitic diimide 2 and anthraquinone 3 in the presence of lithium and potassium ions, respectively. Consequently, two novel cascade complexes with neutral molecules as bridging species were formed in solution and in the solid state, which were structurally studied by NMR, MS spectra, and X-ray methods. Moreover, we also found that the association and dissociation of the complexes could be easily achieved by the addition and removal of lithium or potassium ions, which resulted in three cation-controlled switchable processes.     

Complexation of triptycene-based cylindrical macrotricyclic polyether toward diquaternary salts: ion-controlled binding and release of the guests

Triptycene-based cylindrical macrotricyclic polyether 1 has been proved to be an efficient host for the complexation with diquaternary salts in solution and in the solid state. Moreover, it was also found that binding and release of the guest molecules could be easily controlled by the addition and removal of potassium ions.     

A new cryptand: synthesis and complexation with paraquat

[formula: see text] Inspired by folded, nonpseudorotaxane complexes of bis(m-phenylene)-32-crown-10 systems, we synthesized a new bicyclic crown ether containing two 1,3,5-phenylene units linked by three tetra(ethyleneoxy) units. The new cryptand forms a "pseudorotaxane-like" inclusion complex with N,N'-dimethyl-4,4'-bipyridinium bis(hexafluorophosphate) with association constant Ka = 6.1 x 10(4) M-1, 100-fold greater than that of an analogous simple crown ether.     

Synthesis of a symmetric cylindrical bis(crown ether) host and its complexation with paraquat

The first cylindrical host for paraquat derivatives was prepared and characterized by X-ray analysis. Its complex with paraquat has 1:2 stoichiometry. The complexation is statistical and strong as shown by proton NMR characterization, electrospray mass spectrometry, and X-ray analysis.     

Synthesis of triptycene-derived macrotricyclic host containing two dibenzo-[18]-crown-6 moieties and its complexation with paraquat derivatives: Li(+)-ion-controlled binding and release of the guests in the complexes

A new triptycene-derived macrotricyclic host containing two dibenzo-[18]-crown-6 moieties was synthesized and shown to form 1:1 complexes with paraquat derivatives in solution, in which the guests all thread the central cavity of the host. However, it was interestingly found that, depending on the paraquat derivatives with different functional groups, the host can form stable 1:1 or 1:2 complexes in different complexation modes in the solid state, which is significantly different from those of the macrotricyclic host containing two dibenzo-[24]-crown-8 moieties. The formation of the complexes was also proved by the ESI MS and electrochemical experiments. Moreover, it was found that the binding and release of the guests in the complexes could be easily controlled by the addition and removal of lithium ions.     

Formation of ternary complexes between a macrotricyclic host and hetero-guest pairs: an acid-base controlled selective complexation process

A triptycene-based cylindrical macrotricyclic host can include diquat and electron-rich aromatics simultaneously to form stable ternary complexes, which is stabilized not only by a charge-transfer (CT) interaction between electron-rich and electron-deficient guests but also by the face to face pi-stacking interactions between the host and the guests. Moreover, a selective complexation process between a ternary complex containing benzidine and a binary complex can be effectively controlled by the use of acid and base.     

Novel deep-cavity calix[4]arene derivatives with large s-triazine conjugate systems: synthesis and complexation for dyes

Two novel deep-cavity calix[4]arenes 3 and 4 with large s-triazine π-conjugate systems were designed and synthesized in high yields by reacting calix[4]arene with mono phenyl-substituted cyanuric chloride or further substitution with aniline. The liquid–liquid extraction experiment showed that they possessed excellent extraction abilities towards one cationic and three anionic dyes (Orange I, methylene blue, neutral red, brilliant green). The highest extraction percentage of compound 4 was 88.8 % for brilliant green. The complexation UV–Vis spectra of compounds 3 and 4 with four dyes indicated the existences of complexation action between hosts and guests with 1:1 ratio of complexation in DMSO solution. The association constants suggested that the larger π-conjugate system of compound 4 possessed the stronger complexation abilities than that of compound 3. The association constant of compound 4 with BG was as high as 8.1 × 10⁶ M^?1.     

Bis(oxofluorenediyl)oxacyclophanes: synthesis, crystal structure and complexation with paraquat in the gas phase

The first three representatives of the new family of oxacyclophanes incorporating two 2,7-dioxyfluorenone fragments, connected by [-CH(2)CH(2)O-](m) spacers (m=2-4), have been synthesized. The yield of the smallest oxacyclophane (m=2) is considerably higher with respect to the larger ones (m=3 and m=4), which are formed in comparable yields. Molecular modeling and NMR spectra analysis of the model compounds suggest that an essential difference in oxacyclophanes yields is caused by formation of quasi-cyclic intermediates, which are preorganized for macrocyclization owing to intramolecular pi-pi stacking interactions between the fluorenone units. The solid-state structures of these oxacyclophanes exhibit intra- and intermolecular pi-pi stacking interactions that dictate their rectangular shape in the fluorenone backbone and crystal packing of the molecules with the parallel or T-shape arrangement. The crystal packing in all cases is also sustained by weak C--HO hydrogen bonds. FAB mass spectral analysis of mixtures of the larger oxacyclophanes (m=3 and m=4) and a paraquat moiety revealed peaks corresponding to the loss of one and two PF(6) (-) counterions from the 1:1 complexes formed. However, no signals were observed for complexes of the paraquat moiety with the smaller oxacyclophane (m=2). Computer molecular modeling of complexes revealed a pseudorotaxane-like incorporation of the paraquat unit, sandwiched within a macrocyclic cavity between the almost parallel-aligned fluorenone rings of the larger oxacyclophanes (m=3 and m=4). In contrast to this, only external complexes of the smallest oxacyclophane (m=2) with a paraquat unit have been found in the energy window of 10 kcal mol(-1).     

Azomacrocyclic derivatives of imidazole: synthesis, structure, and metal ion complexation properties

New azocrown ethers comprising imidazoles in the macrocycle have been synthesized. Imidazole, 2-methyl-, 4-methyl-, and 4-phenylimidazole were incorporated to form macrocyclic units by coupling with the appropriate bis-diazonium salts. The syntheses were performed under high dilution conditions. The X-ray structure of a water adduct of the 21-membered crown ether derivative of 4-methylimidazole 8 has been solved. Metal cation binding was investigated with the use of UV-vis spectroscopy in acetonitrile, methanol, and methanol-water mixtures. The obtained chromoionophores were tested as ion-carriers in ion-selective membrane electrodes.     

Synthesis of a four-armed cage molecule and its pH-controlled complexation with paraquat

A four-armed cage molecule was synthesized and its pH-controlled host-guest complexation with paraquat was studied. The influences of the location and composition of the arms were also investigated, guiding us to search for more complicate hosts with higher binding affinities.     

Novel derivatives of UDP-glucose: concise synthesis and fluorescent properties

A series of novel 5-substituted UDP-glucose derivatives with interesting fluorescent properties and potential applications as sensors for carbohydrate-active enzymes is reported. An efficient synthesis of the target molecules was developed, centred around the Suzuki-Miyaura reaction of (hetero)arylboronic acids with 5-iodo UDP-glucose. Interestingly, the optimised cross-coupling conditions could also be applied successfully to 5-bromo UMP, but not to 5-bromo UDP-glucose.     

Novel pyrimidinone derivatives: synthesis, antitumor and antimicrobial evaluation

Starting from 6-aryl-4-oxo-2-thioxo-1,2,3,4-tetrahydropyrimidine-5-carbonitrile (4a-d), a series of mono- and dialkyl derivatives 5a-j and 6a, b was synthesized. Hydrazinolysis of 4a, b, d and 5d afforded the hydrazino derivatives 7a-c which were cyclised to give the triazolopyrimidinones 8a-c and the pyrimidotriazinones 9a-c through the reaction with formic acid and chloroacetyl chloride, respectively. Most of the newly synthesized compounds were evaluated for their in-vitro antitumor activity. Compounds 6a and b displayed promising anticancer activity against leukaemia, non-small cell lung, melanoma, and renal cancer. On the other hand, all compounds prepared were screened for their in-vitro antibacterial and antifungal activities. Compounds 5h and j showed significant activity against Staphylococcus aureus, while compounds 5e, 7c and 8c displayed moderate inhibitory activity against Candida albicans.     

Novel synthesis of 2,6-benzothiazonine derivatives

The reaction of 1-alkylamino-1-alkylthio-3-phenyl-3-thioxopropenes with phthaloyl chloride in toluene at 60°C, followed by treatment with triethylamine, afforded 6-alkyl-3-phenyl-2,6-benzothiazonine-1,5,7-triones in good to excellent yields.