10 research outputs found
Correlation between Molecular Structure and Interfacial Properties of Edge or Basal Plane Modified Graphene Oxide
Although graphene oxide (GO) has
been reported to be able to be
edge functionalized or basal-plane functionalized separately, no research
has been done on comparing both the molecular structure and interfacial
properties of them. In this study, an alkyl amine was grafted to the
epoxy group on the basal planes of GO (b-GO) and carboxyl group at
the edges of GO (e-GO) separately by using different synthetic approach.
With the combination of various molecular structure and morphology
characterization methodologies, we proved that the reaction site for
e-GO was only with the carboxyl group at the edge of GO and that for
b-GO was epoxy group on the basal plane of GO, indicating that GO
could be controllably functionalized (fGOs), and the structure of
fGOs could be tuned. Study of the interfacial behavior of fGOs at
liquid–liquid interface showed that the interfacial tension
reducing capability of e-GO was broader than that of b-GO, and for
alkyl oil phase, b-GO was slightly better than e-GO, and both were
better than traditional nonionic surfactant. Study of the interfacial
behavior of fGOs at liquid–solid interface demonstrated that,
after absorption, b-GO arranged vertically on the metal surface, forming
dense, compact, and strong film, while e-GO aligned horizontally to
form loosely assembled film, resulting in higher interfacial shear
strength than that of b-GO. Our results indicate the possibilities
for tuning the interfacial properties of GO at both liquid–liquid
and liquid–solid interfaces, which may be promising in the
potential applications in controlled drug delivery, surface protection,
absorption and separation, lubrication, nanocomposite, and catalyst
fields
Tetranitro-oxacalix[4]crown-Based Host–Guest Recognition Motif and a Related [2]Rotaxane-Based Molecular Switch
Different from so
far reported oxacalix[4]Âcrown-based host–guest
motifs in which oxacalix[4]Âcrowns act only as hydrogen bond acceptors,
a [2]Âpseudorotaxane-type tetranitro-oxacalix[4]Âcrown/urea host–guest
recognition motif was developed in which tetranitro-oxacalix[4]Âcrown
played a role as both a hydrogen bond donor and an acceptor to stabilize
the resulting supramolecular complex. Furthermore, on the basis of
a [2]Âpseudorotaxane complex formed from a tetranitro-oxacalix[4]Âcrown
and an axle containing a secondary ammonium ion and a urea group,
a [2]Ârotaxane-based molecular switch was created, in which the oxacalix[4]Âcrown
wheel was able to reversibly translocate between the secondary ammonium
binding site and the urea binding site of the axle under acid–base
stimulation
[2]Pseudorotaxanes and [2]Catenanes Constructed by Oxacalixcrowns/Viologen Molecular Recognition Motifs
OxacalixÂ[2]ÂareneÂ[2]Âpyrazine
and functional polyether derived oxacalixcrown-6,
-7, and -8 were synthesized, and their host–guest complexation
with paraquat to form [2]Âpseudorotaxanes was studied. The [2]Âpseudorotaxanes
were then successfully used in the construction of two oxacalixcrown-tetracationic
cyclophane [CBPQT<sup>4+</sup>] based [2]Âcatenanes
A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid–Base-Responsive Host–Guest System
An acid–base-responsive
supramolecular host–guest
system based on a planarly chiral A1/A2-diamino-substituted pillar[5]Âarene
(1)/imidazolium ion recognition motif was created. The
pillar[4]Âarene[1]Âdiaminobenzene 1 can bring an electron-deficient
imidazolium cation into its cylindrically shaped cavity under neutral
or basic conditions and release it under acidic conditions
Negative Cooperativity in the Binding of Imidazolium and Viologen Ions to a Pillar[5]arene-Crown Ether Fused Host
A pillar[5]Âarene-crown
ether fused bicyclic host <b>1</b> was found to be able to recognize
an imidazolium ion <b>G1</b> by its pillar[5]Âarene subunit and
a viologen ion <b>G2</b> by its crown ether receptor discriminatively.
The simultaneous binding
of <b>G1</b> and <b>G2</b> by <b>1</b> resulted
in the formation of a three-component host–guest complex <b>G1⊂1⊃G2</b>. Negative heterotropic cooperative effects
were displayed by <b>G1</b> and <b>G2</b> in their binding
to <b>1</b> and were investigated by stepwise bindings of <b>G1</b> and <b>G2</b> to <b>1</b>
A1/A2-Diamino-Substituted Pillar[5]arene-Based Acid–Base-Responsive Host–Guest System
An acid–base-responsive
supramolecular host–guest
system based on a planarly chiral A1/A2-diamino-substituted pillar[5]Âarene
(<b>1</b>)/imidazolium ion recognition motif was created. The
pillar[4]Âarene[1]Âdiaminobenzene <b>1</b> can bring an electron-deficient
imidazolium cation into its cylindrically shaped cavity under neutral
or basic conditions and release it under acidic conditions
A Shape-Persistent Cryptand for Capturing Polycyclic Aromatic Hydrocarbons
A shape-persistent
cryptand <b>1</b>, containing two face-to-face
oriented electron-deficient 2,4,6-triphenyl-1,3,5-triazine units separated
by approximately 7 Ã…, and bridged by two rigid 1,8-naphthyridine
linkers and a pentaethylene
oxide loop, is created for capturing polycyclic aromatic
hydrocarbons. Cryptand <b>1</b> formed 1:1 complexes with PAH
guest molecules, such as phenanthrene (<b>6</b>), anthracene
(<b>7</b>), pyrene (<b>8</b>), triphenylene (<b>9</b>), and tetraphene (<b>10</b>). The single-crystal structure
of complex <b>6⊂1</b> revealed that <b>6</b> was
included in the cavity of <b>1</b> via face-to-face π···π
stacking interactions. Soaking crystalline <b>1</b> in a toluene
solution of anthracene resulted in anthracene from the toluene solution
being picked up by the crystalline solid of <b>1</b>
Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host
A novel tricylic
host molecule <b>1</b> that consists of
two pillar[5]Âarene units and a crown ether ring was found to selectively
bind two kinds of guest molecules with different shapes, sizes, and
electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits,
to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association
between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>
Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host
A novel tricylic
host molecule <b>1</b> that consists of
two pillar[5]Âarene units and a crown ether ring was found to selectively
bind two kinds of guest molecules with different shapes, sizes, and
electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits,
to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association
between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>
Selectivity and Cooperativity in the Binding of Multiple Guests to a Pillar[5]arene–Crown Ether Fused Tricyclic Host
A novel tricylic
host molecule <b>1</b> that consists of
two pillar[5]Âarene units and a crown ether ring was found to selectively
bind two kinds of guest molecules with different shapes, sizes, and
electronic constitutions, namely 1,4-dicyanobutane <b>G1</b> and paraquat <b>G2</b>, with its two macrocyclic subunits,
to form a four-component complex <b>2G1⊂1⊃G2</b>. An <sup>1</sup>H NMR study of stepwise bindings of <b>G1</b> and <b>G2</b> to host <b>1</b> in CDCl<sub>3</sub>/DMSO-<i>d</i><sub>6</sub> revealed that the strength of the association
between complex <b>2G1⊂1</b> and guest <b>G2</b> was only one-fourth of that between free <b>1</b> and <b>G2</b>, demonstrating a negative heterotropic cooperativity of <b>G1</b> in the binding of <b>G2</b> to host <b>1</b>