Showing papers by "Wanhua Wu published in 2022"

Host‐guest Complexation‐induced Aggregation based on Pyrene‐modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence

Abstract: Abstract: Several γ-cyclodextrin (CD) derivatives mono- or di-substituted by pyrenes at the primary rim of CD were demonstrated to aggregate into nano-strips in aqueous solutions, with the pyrene moieties interpenetrating into g-CD cavities. The hydrophobic complexation-induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant ECD and CPL activities, giving unprecedently high g abs and g lum values up to 4.3 × 10 -2 and 5.3 × 10 - 2 , respectively. The aggregates lead to excimer emission with high quantum yields and show B CPL and B i CPL up to 338. 6 M -1 cm - 1 and 169.3 M -1 cm - 1 , respectively.

The More the Slower: Self-Inhibition in Supramolecular Chirality Induction, Memory, Erasure, and Reversion.

Abstract: Self-inhibition has been observed widely in hierarchical biochemical processes but has yet to be demonstrated in pure molecular physical rather than chemical or biological processes. Herein, we report an unprecedented example of self-inhibition during the supramolecular chirality induction, memory, erasure, and inversion processes of pillar[5]arene (P[5]) derivatives. The addition of chiral alanine ethyl ester to bulky substituent-modified P[5]s led to time-dependent chirality induction due to the shift in the equilibrium of the SP and RP conformers P[5]. Intriguingly, more chiral inducers led to more intensive final chiroptical properties but lower chiral induction rates. Thus, the chiral inducer plays the role of both activator and inhibitor. Such self-inhibition essentially arises from kinetics manipulation of three tandem equilibria. Moreover, the chiroptical properties could be memorized by replacing the chiral inducer with an achiral competitive binder, and the chiroptical signal could be erased and reversed by an antipodal chiral inducer, which also showed the self-inhibition property.

Host-guest Complexation-induced Aggregation based on Pyrene-modified Cyclodextrins for Improved Electronic Circular Dichroism and Circularly Polarized Luminescence.

Abstract: Several γ-cyclodextrin (CD) derivatives mono- or di-substituted by pyrenes at the primary rim of CD were demonstrated to aggregate into nano-strips in aqueous solutions, with the pyrene moieties interpenetrating into g-CD cavities. The hydrophobic complexation-induced aggregation provides a rigid chiral environment for the pyrenes and leads to significant ECD and CPL activities, giving unprecedently high g abs and g lum values up to 4.3 × 10 -2 and 5.3 × 10 - 2 , respectively. The aggregates lead to excimer emission with high quantum yields and show B CPL and B i CPL up to 338. 6 M -1 cm - 1 and 169.3 M -1 cm - 1 , respectively.

Triplet-triplet annihilation upconversion in LAPONITE®/PVP nanocomposites: absolute quantum yields of up to 23.8% in the solid state and application to anti-counterfeiting.

Abstract: The low quantum efficiency in the solid phase and the highly efficient quenching by oxygen are two major weaknesses limiting the practical applications of triplet-triplet annihilation (TTA) upconversion (UC). Herein, we report an organic-inorganic hybrid nanocomposites fabricated by self-assembly of LAPONITE® clay and poly(N-vinyl-2-pyrrolidone) (PVP), which serves as excellent matrix for solid-state TTA-UC even in air. In the hybrid hydrogel doped by TTA-UC components, the anionic acceptors are arranged in an ordered manner at the nano-disk edge through electrostatic attraction, which avoids haphazard accumulation of the acceptors and allows for highly efficient inter-acceptor triplet energy migration. Moreover, the entangled PVP could not only protect the triplet excitons from oxygen quenching but even proactively eliminate oxygen by photoirradiation. Significantly, the dried gel prepared by completely removing water from the hydrogel gave absolute UC quantum efficiencies of up to 23.8% (out of a 50% maximum), which is the highest TTA-UC efficiency obtained in the solid state. The dried gels are readily made into powder by grinding with maintained UC emissions, making them convenient for application to information encryption and anti-counterfeiting security by virtue of the high UC quantum efficiency and insensitivity to oxygen.

Catalytic Chiral Photochemistry Sensitized by Chiral Hosts-Grafted Upconverted Nanoparticles.

Abstract: Singlet chiral photocatalysis is highly challenging. Herein, we report fluorescence resonance energy transfer (FRET)-based chiral photocatalysis with γ-cyclodextrin (CD)-grafted lanthanide-doped upconverted nanoparticles (UCNP). The CD-modified UCNP strongly emits in the UV wavelength region upon excitation with a 980 nm laser, which selectively sensitizes the photosubstrates complexed by CD on the surface of UCNP through FRET. Therefore, enantiodifferentiating photocyclodimerization of anthracene or naphthalene derivatives sensitized by the CD-modified UCNP gives photoproducts in good enantioselectivity even in the presence of a catalytic amount of CD-modified UCNP. Moreover, the photocatalysts are readily separated and could be reused for at least six cycles without decreasing the enantioselectivity.

BODIPY-conjugated bis-terpyridine Ru(II) complexes showing ultra-long luminescence lifetimes and applications to triplet-triplet annihilation upconversion.

Abstract: The poor excited-state properties of bis-terpyridine Ru(II) complexes have significantly limited the applications of these complexes as sensitizers in photocatalysis and triplet-triplet annihilation upconversion. In the present work, two novel ruthenium bis-terpyridine complexes (Ru-1 and Ru-2) conjugated with visible-light-harvesting bodipy chromophores were synthesized. These complexes showed strong absorption of visible light, the bodipy-localized intraligand triplet state (3IL) was efficiently populated, and the phosphorescence of bodipy at room temperature in both complexes was observed. The luminescence lifetimes of these complexes were significantly prolonged, with that of the heteroleptic complex Ru-2 prolonged to 37.9 μs and that of the homoleptic bis-terpyridine complex Ru-1 unprecedentedly prolonged to 356 μs, which was hundreds of times longer than the current longest emissive state achieved in ruthenium terpyridine complexes. The ultra-long triplet lifetimes and strong visible-light absorbing ability made them new candidates of triplet sensitizers, and were first applied to TTA-UC for terpyridine Ru(II) complexes with a Ru-1/Py system showing a ΦUC of 2.93% in dilute solutions at concentrations as low as 1.0 μM.

pH-Controlled Enantioselectivity Switching of Irregular Photodi-mers in Photocyclodimerization of 2-Anthracenecarboxylic acid-mediated with β-cyclodextrin Derivatives

Abstract: A series of modified β-cyclodextrin (CDx’s) with a mono/bis-quinoline tether were synthesized and used as chirogenic su-pramolecular host for mediating the enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (AC) at various pH’s....