Chuan-Feng Chen

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.

Chiral induction in phenanthroline-derived oligoamide foldamers: an acid- and base-controllable switch in helical molecular strands.

A series of phenanthroline-derived oligoamides bearing a chiral (R)-phenethylamino end group were synthesized that displayed chiral helical induction and subsequently formed one-hand helical foldamers in solution. Moreover, an acid- and base-controllable switch in the helical molecular strands was observed, which has been demonstrated by NMR, UV-vis, and circular dichroism spectroscopy.

Synthesis of new chromogenic calix[4]crowns and molecular recognition of alkylamines

Abstract A new type of calix[4]crown containing ester group 3 has been synthesized and selectively nitrated to give 4 or ipso-nitrated to give 6. By nitration a novel calixcrown 5 containing a quinone segment was obtained. These nitrated calixcrowns have been used as chromogenic hosts for complexing alkylamines and the factors affecting recognition are discussed.

Complexation of Triptycene-Based Macrotricyclic Host toward (9-Anthracylmethyl)benzylammonium Salt: A Ba2+ Selective Fluorescence Probe

A new triptycene-based macrotricyclic host containing two dibenzo-30 crown-10 moieties (1) has been synthesized. It could form a 1:2 stable complex 1 x 3(2) with (9-anthracylmethyl)benzylammonium salt (3) in both solution and solid state, in which the 9-anthracyl groups were selectively positioned inside the cavity of the host. Moreover, the complexation and disassociation of complex 1 x 3(2) could be chemically controlled by the addition of base and acid. It was also found that Ba(2+) ion could considerably induce the fluorescence enhancement of complex 1 x 3(2), which might thus be utilized as a selective supramolecular fluorescence probe for Ba(2+) ion. Fluorescence and (1)H NMR spectroscopic titrations further showed that the complexation between complex 1 x 3(2) and barium ions underwent a two-step process.

Synthesis of a Triptycene-Derived Bisparaphenylene-34-crown-10 and Its Complexation with Both Paraquat and Cyclobis(paraquat-p-phenylene)

A novel triptycene-derived bisparaphenylene-34-crown-10 (1) has been synthesized, and shown to form 1:1 stable complexes with both the paraquat G1.2PF(6) and the cyclobis(paraquat-p-phenylene) G2.4PF(6) in different complexation modes in solution and solid state. Moreover, it was found that both the complexes 1.G1.2PF(6) and 1.G2.4PF(6) were formed by charge transfer interactions, and did not dissociate upon the first one-electron reduction process of the bipyridinium ring.

Synthesis, Structure, and Binding Property of Pentiptycene-Based Rigid Tweezer-like Molecules

A series of pentiptycene-derived rigid tweezer-like molecules have been efficiently synthesized, and their structures have been determined by NMR, MS spectra, and X-ray analysis. Moreover, it was also found that molecular tweezer 15 showed efficient binding ability toward C(60).

Folding-Induced Selective Hydrogenation of Helical 9,10-Anthraquinone Analogues

The first selective catalytic hydrogenation induced by the artificial helix based on oligo(phenanthroline dicarboxamide)s containing a 9,10-anthraquinone subunit is described. Due to the steric hindrance within the helically folded oligomers, the selective reductions of the anthraquinone units were completely different from those of model substrates, which subsequently mimicked the enzyme catalysis for preventing some reactions from occurring.