4 research outputs found
Propargylic Dialkyl Effect for Cyclobutene Formation through Ir(III)-Catalyzed Cycloisomerization of 1,6-Enynes
The propargylic dialkyl effect (PDAE) has a significant
impact
on the cyclization reaction of enynes, partly reflected in changing
the types of products. Herein, we described the influence of the propargylic
dialkyl effect on the Ir(III)-catalyzed cycloisomerization of 1,6-enynes
to provide strained cyclobutenes. A series of substituted 1,6-enynes
were proved to be excellent substrate candidates in the presence of
[Cp*IrCl2]2 in toluene. Mechanistic investigation,
based on deuterium labeling experiments and control experiments, indicated
that the propargylic dialkyl effect might boost C(sp)-H activation
by preventing the coordination of active iridium species to the C(sp)C(sp)
bond of enynes. This finding contributes to the fundamental understanding
of enyne cyclization reactions and offers valuable insight into the
propargylic dialkyl effect
Enhanced Davydov Splitting in Crystals of a Perylene Diimide Derivative
We
report the polarized absorption spectra of high-quality, thin
crystals of a perylene diimide (PDI) species with branched side chains
(<b>B2</b>). The absorption spectrum shows exemplary polarization-dependent
H-like and J-like aggregate behavior upon orthogonal excitation, with
a sizable Davydov splitting (DS) of 1230 cm<sup>–1</sup> and
peak to peak splitting of 3040 cm<sup>–1</sup>. The experimental
results are compared to theoretical calculations with remarkable agreement.
The theoretical analysis of the polarized absorption spectra shows
evidence of a high degree of intermolecular charge transfer, which,
along with Coulombic coupling, conspires to create the unprecedented
DS for this family of dye molecules. The large polarization dependence
of the electronic spectra is attributed to the unique twisted crystal
structure, in which a substantial rotational displacement exists between
neighboring chromophores within a π-stack. These results highlight
the strong sensitivity of the Davydov splitting to intermolecular
geometry in PDI systems
Multimode-Responsive Luminescence of Er<sup>3+</sup> Single-Activated CaF<sub>2</sub> Phosphor for Advanced Information Encryption
The current optical anticounterfeit strategies that rely
on multimode
luminescence in response to the photon or thermal stimuli have significant
importance in the field of anticounterfeiting and information encryption.
However, the dependence on light and heat sources might limit their
flexibility in practical applications. In this work, Er3+ single-doped CaF2 phosphors that show multistimuli-responsive
luminescence have been successfully prepared. The as-obtained CaF2:Er3+ phosphor exhibits green photoluminescence
(PL) and color-tunable up-conversation (UC) luminescence from red
to green due to the cross-relaxation of Er3+ ions. Additionally,
as-obtained CaF2:Er3+ phosphors also display
green mechano-luminescence behavior, which is induced by the contact
electrification between the CaF2 particles and PDMS polymers,
enabling the phosphor to flexibly respond to mechanical stimuli. Moreover,
feasible anticounterfeiting schemes with the capability of multistimuli-responsive
and flexible decryption have been constructed, further expanding the
application of optical materials in the field of advanced anticounterfeiting
and information encryption
Enhanced Storage Capacity via Anion Substitution for Advanced Delayed X‑ray Detection
X-ray radiation information storage, characterized by
its ability
to detect radiation with delayed readings, shows great promise in
enabling reliable and readily accessible X-ray imaging and dosimetry
in situations where conventional detectors may not be feasible. However,
the lack of specific strategies to enhance the memory capability dramatically
hampers its further development. Here, we present an effective anion
substitution strategy to enhance the storage capability of NaLuF4:Tb3+ nanocrystals attributed to the increased
concentration of trapping centers under X-ray irradiation. The stored
radiation information can be read out as optical brightness via thermal,
980 nm laser, or mechanical stimulation, avoiding real-time measurement
under ionizing radiation. Moreover, the radiation information can
be maintained for more than 13 days, and the imaging resolution reaches
14.3 lp mm–1. These results demonstrate that anion
substitution methods can effectively achieve high storage capability
and broaden the application scope of X-ray information storage