The competitive conformation chirality of dynamically racemic water-soluble pillar[5]arene WP5 can be induced by 19 different L-amino acid ethyl ester hydrochlorides. Among them, L-Arg-OEt and 18 other L-amino acid ethyl ester hydrochlorides can induce the opposite-handedness conformation of WP5. This was ascribed to the different binding models with a side-chain moiety or ethyl ester moiety of amino acids toward the cavity of WP5.
Chiral α‐amino acids play critical roles in the metabolic process in nearly all life forms. So far, chiral recognition of α‐amino acids has mainly focused on the determination of l/d enantiomers. Herein, selection of planar chiral conformations between water‐soluble pillar[5]arene WP5 and pillar[6]arene WP6 was observed due to α‐side chain or ethyl ester moieties of l‐α‐amino acid ethyl ester hydrochlorides binding with WP5 and WP6, respectively. Therefore, α‐side chain and ethyl ester moieties of l‐α‐amino acid ethyl ester hydrochlorides were recognized by observing the induced CD signal and its inversion. This is a rare example of being able to detect the chiral region around α‐carbon of a chiral α‐amino acid molecule.
A stoichiometry-controlled chirality induction was successfully achieved through coassemblies of amphiphilic tetraphenylethylene derivative TPEA, γ-cyclodextrin (γ-CD), and water-soluble pillar[5]arene WP5 in aqueous solution. Stoichiometric variation of WP5 was found to be an effective strategy to induce topological transition between the pseudo[4]rotaxane and the vesicular form. Interestingly, the formation of pseudo[4]rotaxane triggered dual chirality induction from chiral γ-CD to TPEA (negative ICD 1 ), and then, to dynamically racemic WP5 (positive ICD 2 ), whereas both ICD 1 and ICD 2 were silent in the vesicular form.
A crown-shaped cyclotriveratrylene
(CTV) analogue
with persubstituted arene unitsnamely, cyclotrixylohydroquinoylene
(CTX)was synthesized from tetrasubstituted o-xylohydroquinone. Importantly, a series of CTX derivatives were prepared by introducing second bridged methylene,
phenylphosphine oxide, and dimethylsilyl at the middle rim, referred
to as CTX[CH
2
], CTX[P(O)Ph], and CTX[SiMe
2
], respectively, with the completely locked crown conformation,
leading to the formation of unique C3-symmetric Chinese
censer-shaped pocket structures. In addition, the water-soluble CTX[CH
2
] derivative (WCTX[CH
2
]) was synthesized
from CTX[CH
2
] by
simple oxidation reaction with the modification at the upper rim,
and its host–guest interaction with methyl viologen in water
was investigated.
Chirality at different levels is widely observed in nature, but the clue to connect it all together, and the way chirality transfers among different levels are still obscure. Herein, a l-/d-lysine-based self-assembly system was constructed, in which two-step chirality transfer among three different levels was observed in aqueous solution. The chirality originated from the point chirality of amino acid derivatives l-/d-PyLys hydrochloride, and was transferred to the planar conformational chirality of water-soluble pillar [5] arene pR-/pS-WP5. Then, with the aid of pR-/pS-WP5, nanoparticles were formed that exhibited L-/R-handed circularly polarized luminescence with a dissymmetry factor of up to � 0.001, arising from pyrene chiral excimers. This multilevel chirality transfer not only provides a perspective to trace potential clues, and to pursue certain ways by which the chirality transfers, but also offers a strategy to create controllable CPL emission in aqueous media.
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