Green Synthesis of Leaning Tower[6]arene-Mediated Gold Nanoparticles for Label-Free Detection

Article abstract of DOI:10.1021/acs.orglett.1c01300

Here a facile synthesis strategy toward carboxylated leaning tower[6]arene (CLT6)-mediated gold nanoparticles (CLT6-AuNPs) without external energy sources and reducing agents has been developed. Due to the cavity structure of CLT6, CLT6-AuNPs with a controllable particle size show good stability and excellent performance in label-free detection of diquat. Significantly, we reveal the reduction mechanism of AuNP formation, which is the cleavage of some phenyl ether bonds of CLT6 to produce reductive phenols, thus reducing Au3+ to AuNPs.

Full text of DOI:10.1021/acs.orglett.1c01300

pubs.acs.org/OrgLett
Letter
Green Synthesis of Leaning Tower[6]arene-Mediated Gold
Nanoparticles for Label-Free Detection
Hao Zhang, Xin Wang, Kun-Tao Huang, Feng Liang,* and Ying-Wei Yang*
Cite This: Org. Lett. 2021, 23, 4677−4682
Read Online
sı
*
Metrics & More
Article Recommendations
Supporting Information
ACCESS
ABSTRACT: Here a facile synthesis strategy toward carboxylated leaning tower[6]arene
(CLT6)-mediated gold nanoparticles (CLT6-AuNPs) without external energy sources and
reducing agents has been developed. Due to the cavity structure of CLT6, CLT6-AuNPs
with a controllable particle size show good stability and excellent performance in label-free
detection of diquat. Significantly, we reveal the reduction mechanism of AuNP formation,
which is the cleavage of some phenyl ether bonds of CLT6 to produce reductive phenols,
thus reducing Au3+ to AuNPs.
Leaning tower[6]arene (LT6) has received a great deal of
old nanoparticles (AuNPs) have been extensively
Gexplored for applications in catalysis, sensing, detection, attention due to its favorable cavity adaptability and intensive
host−guest binding capability.21−26 Recently, we employed
biomedicine, and electronics, because of their unique physical
and chemical properties.1−4 However, the rapid development
carboxylated LT6 for in situ preparation of AuNPs via a
hydrothermal method.27 As opposed to the previous method
of these application fields also raises higher requirements for
with a harsh temperature, herein we develop an energy-saving
and environmentally friendly synthetic strategy toward CLT6-
functionalized AuNPs (CLT6-AuNPs) for sensing and
detection of diquat herbicide. The particle size of CLT6-
AuNPs is controlled by adjusting the molar ratio of HAuCl4 to
CLT6. Importantly, the reduction mechanism of CLT6 has
been revealed for the first time. The phenols produced by the
cleavage of phenyl ether bonds on CLT6 play a key role in the
reduction of Au3+ to AuNPs. This study fills the gap in the
reduction mechanism of water-soluble supramolecular macro-
cycles and lays a theoretical foundation for the development of
macrocycle−gold hybrid nanomaterials.
A facile method was used to synthesize AuNPs, where only
CLT6 and HAuCl4 were mixed in a 1:1 molar ratio in water for
24 h without heating or stirring (Scheme 1). The resulting
wine-red solution indicated the formation of CLT6-AuNPs. In
Figure 1b, the powder X-ray diffraction (XRD) pattern
confirmed that the diffraction peaks of CLT6-AuNPs
corresponded to the face-centered-cubic Au (JCPDS Card
the stability and functionality of AuNPs, such as the specific
recognition capabilities for pollutants and biological receptors.
To address such challenges, surface modification has become a
common and effective strategy.5,6 Over the past several years,
water-soluble supramolecular macrocycles stand out among
various modifiers due to their excellent stability and unique
host−guest recognition properties.7−11 The marriage of
supramolecular macrocycles and AuNPs not only provides
new possibilities for the construction of functional hybrid
nanomaterials but also greatly strengthens their application
potentials.12−17
Generally, robust and quick chemical reduction has been a
mainstream strategy for synthesis.12−14 However, some harsh
chemical reducing agents are environmentally unfriendly.
Moreover, most reducing agents not only occupy the active
sites of AuNPs for catalysis but also introduce biotoxicity to
prevent their application in biomedicine.18 Recently, several
water-soluble supramolecular macrocycle-functionalized
AuNPs have been prepared via a hydrothermal method
without additional reducing agents.10,16 Despite substantial
efforts, an unclear reduction mechanism and the harsh
conditions still limit the large-scale production and application
of AuNPs.19,20 Therefore, the reaction mechanism needs to be
explored to develop energy-efficient and environmentally
friendly approaches for preparing AuNPs or other metal-
based nanoparticles.
Received: April 26, 2021
Published: May 28, 2021
https://doi.org/10.1021/acs.orglett.1c01300
© 2021 American Chemical Society
Org. Lett. 2021, 23, 4677−4682
4677

Organic Letters
pubs.acs.org/OrgLett
Letter
temperature over 3 months (Figure S18). In addition, the
particle size of CLT6-AuNPs was controlled by adjusting the
molar ratio of CLT6 to HAuCl4. Simultaneously, the surface
plasmon resonance (SPR) of CLT6-AuNPs was blue-shifted
from 539 to 518 nm (Figure 1d), and the corresponding
spheres from ∼10 to ∼3.5 nm in diameter were observed
(Figures S19 and S20). These illustrated that a relatively
smaller final particle size of AuNPs was observed upon
addition of more CLT6 to stabilize the particle surface and
overcome the increased surface free energy of larger AuNPs,
which promotes nanoparticle agglomeration to afford a stable
state.31−33 Therefore, size-tunable CLT6-AuNPs have been
successfully prepared via such a one-step synthesis strategy at
ambient temperature without external reducing agents.
Scheme 1. Representation of the Facile Synthesis of CLT6-
AuNPs to Detect Diquat and Demonstration of the
Reduction Mechanism of CLT6 in the AuNP Synthesis with
the Assistance of a Series of Control Compounds
However, the reduction mechanism of CLT6 is still under
debate in the literature.27 Compared with other reducing
agents, such as hydroxylamine, CLT6 has no obvious reducing
functional group.34,35 Therefore, various control experiments
have been performed to explore the reduction mechanism
(Figure 2). As a supramolecular macrocycle, the electro-
Figure 2. Photographs at different periods of the solutions of HAuCl4
(0.25 mM) and (a) blank, (b) CLT6 (0.25 mM), (c) M1 (0.50 mM),
(d) CP5 (0.25 mM), (e) M2 (1.00 mM), (f) M3 (1.00 mM), (g) SP
(1.00 mM), and (h) DS (1.00 mM).
negative cavity of CLT6 was considered the most likely
electron provider.21 To justify this inference, the monomer of
CLT6 (M1) was used to prepare AuNPs in the same manner.
The colorless solution turned purple after 3 days, indicating
the reducibility of M1 (Figure 2c). For further validation, a
permethylated LT6 (MeLT6) was selected to investigate the
function of the cavity structure. Dissolved in a THF/H2O
mixture [4:1 (v/v)] with HAuCl4, CLT6 could reduce Au3+ to
AuNPs while MeLT6 cannot (Figure S21). These results
reveal that the reducibility is attributed to the substructure of
CLT6 rather than its cavity.
To facilitate research, M1 was further simplified to obtain
sodium 2,2′-[1,4-phenylenebis(oxy)]diacetate (M2).30 With a
1:4:2 CLT6:M1:M2 molar ratio, M2 exhibited a large reducing
power and the solution turned red within minutes (Figure 2e).
Moreover, carboxylated pillar[5]arene (CP5) containing the
substructure of M2 was introduced into the HAuCl4 solution.
The results manifested that the reducibility of CP5 was no
lower than that of CLT6 (Figure 2d). Moreover, compared
with M1-mediated AuNPs and M2-mediated AuNPs, CLT6-
Figure 1. (a) FT-IR spectra of CLT6 and CLT6-AuNPs. (b) XRD
pattern. (c) HR-TEM image of CLT6-AuNPs. (d) UV−vis spectra
and photographs of CLT6-AuNPs obtained from different ratios of
HAuCl4 and CLT6. [HAuCl4] = 0.25 mM.
No. 04-0784).28 The distance between adjacent planes
matched that of the Au(111) planes (2.35 Å) in the high-
resolution transmission electron microscopy image (HR-TEM)
(Figure 1c), validating the successful preparation of CLT6-
AuNPs.29 Moreover, CLT6 was modified on the surface of
AuNPs through O−Au coordination bonds,14,15 and character-
istic bands of −COO− at 1654 and 1407 cm−1 were clearly
observed in the Fourier transform infrared (FT-IR) spectrum
(Figure 1a).30 Meanwhile, the excellent water solubility of
CLT6 ensured the good stability and dispersibility of CLT6-
AuNPs that remained stable and homogeneous at room
4678
https://doi.org/10.1021/acs.orglett.1c01300
Org. Lett. 2021, 23, 4677−4682

Organic Letters
pubs.acs.org/OrgLett
Letter
AuNPs exhibited good stability and controllable particle size
during the preparation. These suggested that the reducibility of
CLT6 was associated with substructure M2 and that it can be
applied in other water-soluble supramolecular macrocycles
containing such a substructure.
After that, in-depth research was conducted to investigate
the functional group of M2. Initially, to access the reducibility
of carboxylate groups, disodium sebacate (DS), containing
only carboxyl and alkanes, was mixed with a HAuCl4 solution.
The resulting colorless solution precluded the value of the
carboxylate group for reducing Au3+ (Figure 2h). Subse-
quently, sodium 4,4′-[1,4-phenylenebis(oxy)]dibutanoate
(M3) with carbon chains longer than M2 was used to explore
the role of active methylene. Surprisingly, the blue-purple
solution implied that the reducibility was independent of the
active methylene (Figure 2f). Compared to the structures of
these molecules, the phenyl ether bond aroused our attention.
Hence, sodium phenylacetate (SP) without a phenyl ether
bond was introduced as a contrast. SP shows no reducibility,
suggesting an important role of the phenyl ether bond of M2 in
the reduction.
Given the reducibility of the phenyl ether bond, the
reduction mechanism of M2 and CLT6 can be suggested.
Although the cleavage of ether bonds generally requires protic
acids or Lewis acids as catalysts in the traditional reaction,36,37
the catalytic dealkylation of ethers to alcohols on certain metal
surfaces has been reported.38 Au(111) on CLT6-AuNPs is one
such metal surface. Due to the p−π conjugation between the
oxygen atom and the benzene ring, cleavage of the phenyl
ether bond will generate acetate ions and phenols (Figure
3a).39,40 Then, phenols reduce Au3+ for the fabrication of
AuNPs with the generation of benzoquinone. Accordingly,
confirming these reaction products is important in elucidating
the reduction mechanism.
Figure 3. (a) Reaction mechanism showing the cleavage of phenyl
ether bonds of M2 produces reductive phenols for reducing Au3+. (b)
Photographs at different periods of solutions containing HAuCl4
(0.25 mM) and CLT6 (0.25 mM) or M2 (1.00 mM) with the
addition of methylbenzene (1.00 mM), benzyl chloride (1.00 mM), or
benzyl bromide (1.00 mM).
Considering the strong reducibility of phenol, it can be
proved indirectly by investigating the impact of the additional
benzyl groups, which could consume the phenolic hydroxyl
groups.41 Three phenolic hydroxyl trapping agents with
different reactivities, including methylbenzene (no reactivity),
benzyl chloride (mild reactivity), and benzyl bromide (strong
reactivity), were added to the solutions (CLT6 and HAuCl4, or
M2 and HAuCl4) separately. Phenomenally, the fuchsia
solutions indicated that the reducibility of CLT6 and M2
was left undisturbed by methylbenzene or benzyl chloride
(Figure 3b). Conversely, no AuNPs were formed with the
addition of benzyl bromide for 3 days, because phenols
generated by the cleavage of phenyl ether bonds lost their
reducibility after reacting with benzyl bromide. Thus, the
existence of phenols has been confirmed in the reduction
process.
Certainly, other reaction products were also identified by 1H
NMR spectroscopy. After centrifugation and freeze-drying, a
new signal at 6.90 ppm can be ascribed to the benzoquinone in
the 1H NMR spectrum of the M2-mediated AuNP (M2-
AuNP) supernatant, further attesting to the presence of
phenols and the correctness of the postulated mechanism
(Figure 4a). Equivalently, multiple new signals (7.75−7.78 and
7.39−7.33 ppm) appeared near the benzene ring H signals of
CLT6, because the cleavage of phenyl ether bonds led to the
changes in the chemical environment of hydrogen atom on the
benzene ring (Figure 4a). In addition, the signals of CLT6 or
M2 were still present in the 1H NMR spectrum, indicating that
only part of CLT6 or M2 served as a reducing agent for the
Figure 4. 1H NMR spectra (D2O, 600 MHz, 298 K) of the
supernatants of M2-AuNPs and CLT6-AuNPs after centrifugation
and freeze-drying. The initial concentrations of M2 and CLT6 were
1.00 and 0.25 mM, respectively. The initial concentrations of HAuCl4
were (a) 0.25 and (b) 2.5 mM for better observation. (c) UV−vis
spectra of CLT6-AuNPs mixed with different concentrations of
diquat. (d) Relationship between the absorbance at the SPR (Aspr) of
CLT6-AuNPs and the concentrations of diquat.
synthesis of AuNPs and the rest were modified on the surface
of generated AuNPs to stabilize the resulting hybrid materials.
Moreover, there was obvious aggregation and precipitation of
4679
https://doi.org/10.1021/acs.orglett.1c01300
Org. Lett. 2021, 23, 4677−4682

Organic Letters
pubs.acs.org/OrgLett
Letter
AuNPs when excess HAuCl4 was added, because of the
constant consumption of phenolics by Au3+ and the lack of a
stabilizer (Figure S22). Excitedly, acetic acid (CH3COOH)
Details of the synthesis of CLT6, M1, M3, and diquat;
preparation of CLT6-AuNPs and PEG-AuNPs; and
host−guest interaction between CLT6 and diquat
(PDF)
1
was observed in the H NMR spectrum of both systems,
solving the puzzle of the reduction mechanism subsequently
(Figure 4b). Confirmation of all reaction products demon-
strated well the reduction mechanism, that phenols produced
by the cleavage of phenyl ether bonds of CLT6 or M2 could
reduce Au3+ to AuNPs.
AUTHOR INFORMATION
Corresponding Authors
■
Feng Liang − The State Key Laboratory of Refractories and
Metallurgy, School of Chemistry and Chemical Engineering,
Wuhan University of Science and Technology, Wuhan
430081, P. R. China; Email: feng_liang@whu.edu.cn
Ying-Wei Yang − The State Key Laboratory of Refractories
and Metallurgy, School of Chemistry and Chemical
Engineering, Wuhan University of Science and Technology,
Wuhan 430081, P. R. China; State Key Laboratory of
Inorganic Synthesis and Preparative Chemistry, International
Joint Research Laboratory of Nano-Micro Architecture
Chemistry (NMAC), College of Chemistry, Jilin University,
Changchun 130012, P. R. China; orcid.org/0000-0001-
8839-8161; Email: ywyang@jlu.edu.cn
In addition to the validation of reaction products, the
catalytic effect of the gold surface was also proven. To illustrate
this, an equal volume of additional prefabricated CLT6-AuNPs
and carboxymethyl-polyethylene glycol-thiol (SH-PEG-
COOH)-modified AuNPs (PEG-AuNPs) was added to this
system. From the photographs and UV−vis spectra (Figures
S23 and S24), the addition of CLT6-AuNPs promoted the
system to generate AuNPs faster, and PEG-AuNPs that
prevent molecules from contacting the gold surface showed
no positive effect.42 Moreover, when M2 was added to HCl
(0.1 M), water, and NaOH (0.1 M) for 30 days, CH3COOH,
1
CH3COO−, and CH3COO− were detected in the H NMR
spectrum of the three systems mentioned above (Figure S25).
Similarly, CLT6-AuNPs could also be prepared with a series of
initial pH values from 4 to 10, indicating that neither acid nor
alkali environments affect the cleavage of phenyl ether bonds in
CLT6 (Figures S26 and S27).
Authors
Hao Zhang − The State Key Laboratory of Refractories and
Metallurgy, School of Chemistry and Chemical Engineering,
Wuhan University of Science and Technology, Wuhan
430081, P. R. China; State Key Laboratory of Inorganic
Synthesis and Preparative Chemistry, International Joint
Research Laboratory of Nano-Micro Architecture Chemistry
(NMAC), College of Chemistry, Jilin University, Changchun
130012, P. R. China
Xin Wang − State Key Laboratory of Inorganic Synthesis and
Preparative Chemistry, International Joint Research
Laboratory of Nano-Micro Architecture Chemistry (NMAC),
College of Chemistry, Jilin University, Changchun 130012, P.
R. China
To validate that CLT6-AuNPs prepared by this method still
have the host−guest properties, the label-free detection of
diquat, a widely used toxic pesticide, was further demon-
strated.43 First, H NMR and UV−vis spectroscopy indicated
1
that CLT6 could form a stable 2:1 complex with diquat in
water (Figures S28 and S29). Then, upon the addition of
diquat, CLT6-AuNPs would aggregate with each other driven
by the host−guest interactions, resulting in a gradual red-shift
and a decreased absorbance of the SPR peak (Figure 4c).27
Moreover, a strong linear relationship was observed between
the absorbance at the maximum absorption peak of CLT6-
AuNPs and the concentrations of diquat (1−8 μM), indicating
the feasibility and accuracy of diquat detection (Figure 4d).
These results indicate that CLT6-AuNPs inherit the host−
guest properties of CLT6 and have great prospects in chemical
detection applications.
Kun-Tao Huang − The State Key Laboratory of Refractories
and Metallurgy, School of Chemistry and Chemical
Engineering, Wuhan University of Science and Technology,
Wuhan 430081, P. R. China
Complete contact information is available at:
https://pubs.acs.org/10.1021/acs.orglett.1c01300
In conclusion, we prepared CLT6-AuNPs with a controlled
particle size via a green synthesis method without external
energy sources and reducing agents. Moreover, the reduction
mechanism that the reductive phenols produced from the
cleavage of the phenyl ether bonds of CLT6 reduce Au3+ to
AuNPs was proven for the first time. Compared with M1-
mediated AuNPs and M2-mediated AuNPs, CLT6-AuNPs
exhibited good stability, controllable particle size, and excellent
performance in label-free detection of diquat due to the
favorable cavity adaptability and intensive host−guest binding
capability of CLT6. Overall, our studies provide a green
approach for large-scale preparation and commercial applica-
tions of water-soluble supramolecular macrocycle-mediated
AuNPs and build a substantial foundation for the development
of new organic−inorganic hybrid nanomaterials.
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors thank the National Natural Science Foundation of
China (21871108) and Wuhan University of Science and
Technology for financial support.
REFERENCES
■
(1) Liu, J.-C.; Wang, Y.-G.; Li, J. Toward Rational Design of Oxide-
Supported Single Atom Catalysts: Atomic Dispersion of Gold on
Ceria. J. Am. Chem. Soc. 2017, 139, 6190−6199.
(2) Yang, M.; Gong, Y.; Shen, G.; Wang, Z.; Liu, M.; Wang, Q.
Enhanced Benzene Sensing Property of Au-Pd@ZnO and Au-Pt@
ZnO Core-Shell Nanoparticles: The Function of Pt/Pd Decorated
Au-ZnO Hetero-Interface. Mater. Lett. 2021, 283, 128733.
(3) Yang, J.; Wang, F.; Yuan, H.; Zhang, L.; Jiang, Y.; Zhang, X.; Liu,
C.; Chai, L.; Li, H.; Stenzel, M. Recent Advances of Ultra-small
Fluorescent Au Nanoclusters toward Oncological Research. Nanoscale
2019, 11, 17967−17980.
ASSOCIATED CONTENT
■
sı
* Supporting Information
The Supporting Information is available free of charge at
https://pubs.acs.org/doi/10.1021/acs.orglett.1c01300.
4680
https://doi.org/10.1021/acs.orglett.1c01300
Org. Lett. 2021, 23, 4677−4682

Organic Letters
pubs.acs.org/OrgLett
Letter
(4) Wang, B.; Facchetti, A. Mechanically Flexible Conductors for
Stretchable and Wearable E-Skin and E-Textile Devices. Adv. Mater.
2019, 31, 1901408.
(23) Wu, J.-R.; Li, B.; Yang, Y.-W. Separation of Bromoalkanes
Isomers by Nonporous Adaptive Crystals of Leaning Pillar[6]arene.
Angew. Chem., Int. Ed. 2020, 59, 2251−2255.
(5) Bhattarai, J. K.; Neupane, D.; Nepal, B.; Mikhaylov, V.;
Demchenko, A. V.; Stine, K. J. Preparation, Modification, Character-
ization, and Biosensing Application of Nanoporous Gold Using
Electrochemical Techniques. Nanomaterials 2018, 8, 171.
(6) Moraes Silva, S.; Tavallaie, R.; Sandiford, L.; Tilley, R. D.;
Gooding, J. J. Gold Coated Magnetic Nanoparticles: Preparation,
Surface Modification for Analytical and Biomedical Applications.
Chem. Commun. 2016, 52, 7528−7540.
(7) de la Rica, R.; Velders, A. H. Supramolecular Au Nanoparticle
Assemblies as Optical Probes for Enzyme-Linked Immunoassays.
Small 2011, 7, 66−69.
(8) Li, W.; Wang, X.; Jiang, T.; Ma, X.; Tian, H. One-pot Synthesis
of β-cyclodextrin Modified Au Nanocluster with Near-infrared
Emission. Chem. Commun. 2020, 56, 5580−5583.
(9) Montes Garcia, V.; Gomez Gonzalez, B.; Martinez-Solis, D.;
Taboada, J. M.; Jimenez Otero, N.; de Una-Alvarez, J.; Obelleiro, F.;
Garcia Rio, L.; Perez Juste, J.; Pastoriza Santos, I. Pillar[5]arene-Based
Supramolecular Plasmonic Thin Films for Label-Free, Quantitative
and Multiplex SERS Detection. ACS Appl. Mater. Interfaces 2017, 9,
26372−26382.
(10) Premkumar, T.; Geckeler, K. E. Cucurbit[7]uril as a Tool in the
Green Synthesis of Gold Nanoparticles. Chem. - Asian J. 2010, 5,
2468−2476.
(11) Tan, X. P.; Liu, X.; Zeng, W. J.; Zhao, G. F.; Zhang, Z.; Huang,
T.; Yang, L. Control Assembly of Au Nanoparticles on Macrocyclic
Host Molecule Cationic Pillar[5]arene Functionalized MoS2 Surface
for Enhanced Sensing Activity Towards p-Dinitrobenzene. Anal.
Chim. Acta 2019, 1078, 60−69.
(12) Liu, J.; Mendoza, S.; Roman, E.; Lynn, M. J.; Xu, R. L.; Kaifer,
A. E. Cyclodextrin-Modified Gold Nanospheres. Host-Guest Inter-
actions at Work to Control Colloidal Properties. J. Am. Chem. Soc.
1999, 121, 4304−4305.
(13) Lee, T.-C.; Scherman, O. A. Formation of Dynamic Aggregates
in Water by Cucurbit[5]uril Capped with Gold Nanoparticles. Chem.
Commun. 2010, 46, 2438−2440.
(14) Li, H.; Chen, D.-X.; Sun, Y.-L.; Zheng, Y. B.; Tan, L.-L.; Weiss,
P. S.; Yang, Y.-W. Viologen-Mediated Assembly of and Sensing with
Carboxylatopillar[5]arene-Modified Gold Nanoparticles. J. Am. Chem.
Soc. 2013, 135, 1570−1576.
(15) Wang, X.; Liu, Z.-J.; Hill, E. H.; Zheng, Y.; Guo, G.; Wang, Y.;
Weiss, P. S.; Yu, J.; Yang, Y.-W. Organic-Inorganic Hybrid Pillarene-
Based Nanomaterial for Label-Free Detection and Catalysis. Matter
2019, 1, 848−861.
(16) Park, C.; Jeong, E. S.; Lee, K. J.; Moon, H. R.; Kim, K. T.
Carboxylated Pillar[5]arene-Coated Gold Nanoparticles with Chem-
ical Stability and Enzyme-like Activity. Chem. - Asian J. 2014, 9,
2761−2764.
(17) Montes García, V.; Fernández López, C.; Gómez, B.; Pérez
Juste, I.; García Río, L.; Liz Marzán, L. M.; Pérez Juste, J.; Pastoriza
Santos, I. Pillar[5]arene-Mediated Synthesis of Gold Nanoparticles:
Size Control and Sensing Capabilities. Chem. - Eur. J. 2014, 20, 8404−
8409.
(24) Wu, J.-R.; Yang, Y.-W. Synthetic Macrocycle-Based Nonporous
Adaptive Crystals for Molecular Separation. Angew. Chem., Int. Ed.
2021, 60, 1690−1701.
(25) Dai, D. H.; Yang, J.; Zou, Y.-C.; Wu, J.-R.; Tan, L.-L.; Wang, Y.;
Li, B.; Lu, T.; Wang, B.; Yang, Y.-W. Macrocyclic Arenes-Based
Conjugated Macrocycle Polymers for Highly Selective CO2 Capture
and Iodine Adsorption. Angew. Chem., Int. Ed. 2021, 60, 8967−8975.
(26) Li, X.; Han, J.; Qin, J.; Sun, M.; Wu, J.; Lei, L.; Li, J.; Fang, L.;
Yang, Y.-W. Mesoporous Silica Nanobeans Dual-Functionalized with
AIEgens and Leaning Pillar[6]arene-Based Supramolecular Switches
for Imaging and Stimuli-responsive Drug Release. Chem. Commun.
2019, 55, 14099−14102.
(27) Wang, X.; Wu, J.-R.; Liang, F.; Yang, Y.-W. In situ Gold
Nanoparticle Synthesis Mediated by a Water-Soluble Leaning
Pillar[6]arene for Self-Assembly, Detection, and Catalysis. Org. Lett.
2019, 21, 5215−5218.
(28) Wang, Y.; Liu, J.; Wang, Y.; Wang, Y.; Zheng, G. Efficient Solar-
driven Electrocatalytic CO2 Reduction in a Redox-medium-assisted
System. Nat. Commun. 2018, 9, 5003.
(29) Du, J. S.; Chen, P.-C.; Meckes, B.; Kluender, E. J.; Xie, Z.;
Dravid, V. P.; Mirkin, C. A. Windowless Observation of Evaporation-
Induced Coarsening of Au-Pt Nanoparticles in Polymer Nanoreactors.
J. Am. Chem. Soc. 2018, 140, 7213−7221.
(30) Zhang, H.; Wu, J.-R.; Wang, X.; Li, X. S.; Wu, M. X.; Liang, F.;
Yang, Y.-W. One-pot Solvothermal Synthesis of Carboxylatopillar[5]-
arene-Modified Fe3O4 Magnetic Nanoparticles for Ultrafast Separa-
tion of Cationic Dyes. Dyes Pigm. 2019, 162, 512−516.
(31) Jiang, Z.; Le, N. D. B.; Gupta, A.; Rotello, V. M. Cell Surface-
Based Sensing with Metallic Nanoparticles. Chem. Soc. Rev. 2015, 44,
4264−4274.
(32) Houthaeve, G.; Xiong, R.; Robijns, J.; Luyckx, B.; Beulque, Y.;
Brans, T.; Campsteijn, C.; Samal, S. K.; Stremersch, S.; De Smedt, S.
C.; Braeckmans, K.; De Vos, W. H. Targeted Perturbation of Nuclear
Envelope Integrity with Vapor Nanobubble-Mediated Photoporation.
ACS Nano 2018, 12, 7791−7802.
(33) Devadasu, V. R.; Bhardwaj, V.; Ravi Kumar, M. N. V. Can
Controversial Nanotechnology Promise Drug Delivery? Chem. Rev.
2013, 113, 1686−1735.
(34) Hu, M.; Chen, J.; Li, Z.-Y.; Au, L.; Hartland, G. V.; Li, X.;
Marquez, M.; Xia, Y. Gold Nanostructures: Engineering Their
Plasmonic Properties for Biomedical Applications. Chem. Soc. Rev.
2006, 35, 1084−1094.
(35) Can, M. Green Gold Nanoparticles from Plant-derived
Materials: An Overview of the Reaction Synthesis Types, Conditions,
and Applications. Rev. Chem. Eng. 2020, 36, 859−877.
(36) Ryu, I.; Matsubara, H.; Yasuda, S.; Nakamura, H.; Curran, D. P.
Phase-Vanishing Reactions that Use Fluorous Media as a Phase
Screen. Facile, Controlled Bromination of Alkenes by Dibromine and
Dealkylation of Aromatic Ethers by Boron Tribromide. J. Am. Chem.
Soc. 2002, 124, 12946−12947.
(37) Martin, J. R.; Gupta, M. K.; Page, J. M.; Yu, F.; Davidson, J. M.;
Guelcher, S. A.; Duvall, C. L. A Porous Tissue Engineering Scaffold
Selectively Degraded by Cell-Generated Reactive Oxygen Species.
Biomaterials 2014, 35, 3766−3776.
(38) Yang, B.; Lin, H.; Miao, K.; Zhu, P.; Liang, L.; Sun, K.; Zhang,
H.; Fan, J.; Meunier, V.; Li, Y.; Li, Q.; Chi, L. Catalytic Dealkylation
of Ethers to Alcohols on Metal Surfaces. Angew. Chem., Int. Ed. 2016,
55, 9881−9885.
(18) Dahl, J. A.; Maddux, B. L. S.; Hutchison, J. E. Toward Greener
Nanosynthesis. Chem. Rev. 2007, 107, 2228−2269.
(19) Li, H.; Yang, Y.-W. Gold Nanoparticles Functionalized with
Supramolecular Macrocycles. Chin. Chem. Lett. 2013, 24, 545−552.
(20) Singh, J.; Dutta, T.; Kim, K.-H.; Rawat, M.; Samddar, P.;
Kumar, P. ‘Green’ Synthesis of Metals and Their Oxide Nano-
particles: Applications for Environmental Remediation. J. Nano-
biotechnol. 2018, 16, 84.
(39) Leyva-Perez, A.; Combita-Merchan, D.; Cabrero-Antonino, J.
R.; Al-Resayes, S. I.; Corma, A. Oxyhalogenation of Activated Arenes
with Nanocrystalline Ceria. ACS Catal. 2013, 3, 250−258.
(40) Rathore, R.; Bosch, E.; Kochi, J. K. Selective Nitration versus
Oxidative Dealkylation of Hydroquinone Ethers with Nitrogen
Dioxide. Tetrahedron 1994, 50, 6727−6758.
(21) Wu, J.-R.; Mu, A. U.; Li, B.; Wang, C.-Y.; Fang, L.; Yang, Y.-W.
Desymmetrized Leaning Pillar[6]arene. Angew. Chem., Int. Ed. 2018,
57, 9853−9858.
(22) Wu, J.-R.; Yang, Y.-W. High-Performance n-Hexane Purifica-
tion by Nonporous Adaptive Crystals of Leaning Pillar[6]arene. CCS
Chem. 2020, 2, 836−843.
4681
https://doi.org/10.1021/acs.orglett.1c01300
Org. Lett. 2021, 23, 4677−4682

Organic Letters
pubs.acs.org/OrgLett
Letter
(41) Zhang, D.-W.; Zhao, X.; Hou, J.-L.; Li, Z.-T. Aromatic Amide
Foldamers: Structures, Properties, and Functions. Chem. Rev. 2012,
112, 5271−5316.
(42) Zhao, Y.-Q.; Sun, Y.; Zhang, Y.; Ding, X.; Zhao, N.; Yu, B.;
Zhao, H.; Duan, S.; Xu, F.-J. Well-Defined Gold Nanorod/Polymer
Hybrid Coating with Inherent Antifouling and Photothermal
Bactericidal Properties for Treating Infected Hernia. ACS Nano
2020, 14, 2265−2275.
(43) Jones, G. M.; Vale, J. A. Mechanisms of Toxicity, Clinical
Features, and Management of Diquat Poisoning: A Review. J. Toxicol.,
Clin. Toxicol. 2000, 38, 123−128.
4682
https://doi.org/10.1021/acs.orglett.1c01300
Org. Lett. 2021, 23, 4677−4682