10 research outputs found
Electron Injection from Photoexcited Metal–Organic Framework Ligands to Ru<sub>2</sub> Secondary Building Units for Visible-Light-Driven Hydrogen Evolution
We report the design of two new metal–organic
frameworks
(MOFs), Ru-TBP and Ru-TBP-Zn, based on Ru<sub>2</sub> secondary building
units (SBUs) and porphyrin-derived tetracarboxylate ligands. The proximity
of Ru<sub>2</sub> SBUs to porphyrin ligands (∼1.1 nm) facilitates
multielectron transfer from excited porphyrins to Ru<sub>2</sub> SBUs
to enable efficient visible-light-driven hydrogen evolution reaction
(HER) in neutral water. Photophysical and electrochemical studies
revealed oxidative quenching of excited porphyrin by Ru<sub>2</sub> SBUs as the initial step of the HER process and the energetics of
key intermediates in the catalytic cycle. Our work provides a new
strategy to building multifunctional MOFs with synergistic ligands
and SBUs for efficient photocatalysis
Electron Injection from Photoexcited Metal–Organic Framework Ligands to Ru<sub>2</sub> Secondary Building Units for Visible-Light-Driven Hydrogen Evolution
We report the design of two new metal–organic
frameworks
(MOFs), Ru-TBP and Ru-TBP-Zn, based on Ru<sub>2</sub> secondary building
units (SBUs) and porphyrin-derived tetracarboxylate ligands. The proximity
of Ru<sub>2</sub> SBUs to porphyrin ligands (∼1.1 nm) facilitates
multielectron transfer from excited porphyrins to Ru<sub>2</sub> SBUs
to enable efficient visible-light-driven hydrogen evolution reaction
(HER) in neutral water. Photophysical and electrochemical studies
revealed oxidative quenching of excited porphyrin by Ru<sub>2</sub> SBUs as the initial step of the HER process and the energetics of
key intermediates in the catalytic cycle. Our work provides a new
strategy to building multifunctional MOFs with synergistic ligands
and SBUs for efficient photocatalysis
Facile Preparation of Biocompatible Sulfhydryl Cotton Fiber-Based Sorbents by “Thiol–ene” Click Chemistry for Biological Analysis
Sulfhydryl cotton fiber (SCF) has
been widely used as adsorbent for a variety of metal ions since 1971.
Thanks to the abundant thiols on SCF, in this study, we reported a
universal method for the facile preparation of SCF-based materials
using “thiol–ene” click chemistry for the first
time. With the proposed method, two types of SCF-based materials,
phenylboronic acid grafted sulfhydryl cotton fiber (SCF-PBA) and zirconium
phosphonate-modified sulfhydryl cotton fiber (SCF-pVPA-Zr<sup>4+</sup>), were successfully prepared. The grafted functional groups onto
the thiol group of SCF were demonstrated by X-ray photoelectron spectroscopy
(XPS) and energy dispersive X-ray spectroscopy (EDX). The prepared
fibrous materials exhibited excellent fiber strength, good stability
in aqueous or nonaqueous solutions, and great biocompatibility. Moreover,
we developed filter-free in-pipet-tip SPE using these SCF-based materials
as adsorbent for the enrichment of ribonucleosides, glycopeptides
and phosphopeptides. Our results showed that SCF-PBA adsorbent can
selectively capture ribonucleosides and glycopeptides from complex
biological samples. And SCF-pVPA-Zr<sup>4+</sup> adsorbent exhibited
high selectivity and capacity in the enrichment of phosphopeptides
from the digestion mixture of β-casein and bovine serum albumin
(BSA), as well as human serum and nonfat milk digest. Generally, the
preparation strategy can be a universal method for the synthesis of
other functionalized cotton-based adsorbents with special requirement
in microscale biological analysis
A Family of Co<sup>II</sup>Co<sup>III</sup><sub>3</sub> Single-Ion Magnets with Zero-Field Slow Magnetic Relaxation: Fine Tuning of Energy Barrier by Remote Substituent and Counter Cation
The synthesis, structures, and magnetic
properties of a family
of air-stable star-shaped Co<sup>II</sup>Co<sup>III</sup><sub>3</sub> complexes were investigated. These complexes contain only one paramagnetic
Co(II) ion with the approximate <i>D</i><sub>3</sub> coordination
environment in the center and three diamagnetic Co(III) ions in the
peripheral. Magnetic studies show their slow magnetic relaxation in
the absence of an applied dc field, which is characteristic behavior
of single-molecule magnets (SMMs), caused by the individual Co(II)
ion with approximate <i>D</i><sub>3</sub> symmetry in the
center. Most importantly, it was demonstrated that the anisotropy
energy barrier can be finely tuned by the periphery substituent of
the ligand and the countercation. The anisotropy energy barrier can
be increased significantly from 38 K to 147 K
Cobalt(II) Coordination Polymer Exhibiting Single-Ion-Magnet-Type Field-Induced Slow Relaxation Behavior
A one-dimensional cobalt(II) coordination
polymer, [Co(btm)<sub>2</sub>(SCN)<sub>2</sub>·H<sub>2</sub>O]<sub><i>n</i></sub> [btm = bis(1<i>H</i>-1,2,4-triazol-1-yl)methane],
was synthesized and magnetically characterized. The isolated slightly
distorted octahedral Co<sup>II</sup> ion displays field-induced slow
relaxation with a big positive axial and a negative rhombic magnetic
anisotropy (<i>D</i> = 93.9 cm<sup>–1</sup> and <i>E</i> = −10.5 cm<sup>–1</sup>), and the anisotropy
energy barrier is 45.4 K
Solvent-Induced White-Light Emission of Amphiphilic Rod–Rod Poly(3-triethylene glycol thiophene)-<i>block</i>-poly(phenyl isocyanide) Copolymer
A class
of amphiphilic rod–rod diblock copolymers composed of hydrophilic
π-conjugated poly(3-triethylene glycol thiophene) (P3(TEG)T)
and hydrophobic rigid-rod-like poly(phenyl isocyanide) (PPI) was synthesized
in one pot via mechanistically distinct, sequential block copolymerization
with Ni(dppp)Cl<sub>2</sub> as a single catalyst. The hydrophilic
P3(TEG)T homopolymer self-assembled into well-defined nanoparticles
in THF and methanol with different dimensions and exhibited orange-light
emission in THF and red-light emission in methanol. Interestingly,
the resultant P3(TEG)T-<i>b</i>-PPI block copolymers were
found to self-assembled into various well-defined supramolecular structures,
such as nanofibrils in THF, micelles in methanol, and vesicles in
3/2 mixtures of THF and methanol. The assemblies of these block copolymers
in solutions exhibited unique light emissions with the emission color
spanned widely from orange red to blue depending on self-assembled
morphology and solvents used. White light emission can be readily
achieved through the control of self-assembled morphologies by variation
on the solvent composition. Moreover, the light emissions of the block
copolymers were completely reversible, demonstrating the tunable emissions
were indeed ascribed to the morphological transitions of the block
copolymer
Facile Preparation of Regioregular Poly(3-hexylthiophene) and Its Block Copolymers with π‑Allylnickel Complex as External Initiator
Simply prepared π-allylnickel
complexes were used as external initiators for promoting the polymerization
of 2-bromo-3-hexyl-5-chloromagnesiothiophene in a living/controlled
chain growth manner to afford regioregular poly(3-hexylthiophene)
with an allyl terminus. The nickel species on the other chain end
can initiate the block copolymerization of hexadecyloxylallene and
2-bromo-3-hexyl-5-chloromagnesiothiophene to give a well-defined triblock
copolymer containing poly(3-hexylthiophene) and poly(hexadecyloxylallene)
segments in one pot via mechanically distinct, sequential living polymerization.
Furthermore, such π-allylnickel(II) complexes can also catalyze
the polymerization of a range of vinyl monomers, including styrene,
1-methoxy-4-vinylbenzene, and 1-chloro-4-vinylbenzene as well as <i>tert</i>-butyl acrylate, in living/controlled fashion. The active
nickel unit at the growing chain end of these vinyl polymers can also
initiate the block copolymerization of 2-bromo-3-hexyl-5-chloromagnesiothiophene
to give a series of block copolymers containing vinyl polymer and
poly(3-hexylthiophene) segments. The new block copolymerizations have
been demonstrated to proceed in living/controlled chain-extension
manner. The well-defined conjugated block copolymers are isolated
in high yield with controlled molecular weight and tunable compositions
One-Pot Synthesis of Brush Copolymers Bearing Stereoregular Helical Polyisocyanides as Side Chains through Tandem Catalysis
An air-stable phenylethynyl Pd(II)
complex containing a polymerizable
norbornene unit was designed and synthesized. Such a Pd(II) complex
can initiate the living/controlled polymerization of phenyl isocyanide,
giving stereoregular poly(phenyl isocyanide)s in high yields with
controlled molecular weights and narrow molecular weight distributions.
The norbornene unit on the Pd(II) complex can undergo ring-opening
metathesis polymerization (ROMP) with Grubbs’ second-generation
catalyst, affording polynorbornene bearing Pd(II) complex pendants
under a living/controlled manner. Interestingly, the Pd(II) complex
pendants on the isolated polynorbornene are active enough to initiate
the living/controlled polymerization of phenyl isocyanides, yielding
well-defined brush-like copolymers with polynorbornene backbone and
helical poly(phenyl isocyanide) as side chains. <sup>31</sup>P NMR
analyses indicate almost all the Pd(II) units on the polynorbornene
participated in the polymerization, and the grafting density of the
brush copolymer is high. Further studies revealed the brush copolymer
can be readily achieved in one-pot via tandem catalysis. By using
this method, a range of brush copolymers with different structures
and tunable compositions were facilely prepared in high yields with
controlled molecular weights and narrow molecular weight distributions.
The synthesized brush copolymers were revealed to form worm-like cylindrical
morphologies and helical rod architectures in film state by atomic
force microscope observations
Synthesis and Chiroptical Properties of Helical Polyallenes Bearing Chiral Amide Pendants
Two allene derivatives, l- and d-<i>N</i>-(1-(octylamino)-1-oxopropan-2-yl)-4-(propa-1,2-dien-1-yloxy)benzamide
(l-<b>1</b> and d-<b>1</b>), bearing
chiral amide pendants were designed and synthesized. Living polymerizations
of l-<b>1</b> and d-<b>1</b> with allylnickel
complex as a catalyst afforded poly-l-<b>1</b><sub>m</sub> and poly-d-<b>1</b><sub>m</sub> with controlled
molecular weights and narrow molecular weight distributions. These
polymers were found to possess a stable helical conformation with
a preferred handedness in aprotic solvents on the basis of their circular
dichroism (CD) spectra and specific rotation as well as computer simulation.
The helical conformation of the polymers was revealed to be stabilized
by elongation of the repeating unit until the degree of the polymerization
reaches 80. The slightly influence of temperature on the CD spectra
of poly-l-<b>1</b><sub>100</sub> in CHCl<sub>3</sub> indicated the helical conformation was quite stable at least in
the range of 0–55 °C. Although poly-l-<b>1</b><sub>100</sub> showed similar CD spectra in different aprotic solvents,
remarkable decrease was observed upon the addition of protic solvents
such as methanol due to the weakened hydrogen bonding interactions
between the adjacent repeating units. The poly-l-<b>1</b><sub>100</sub> behaves as a pH-responsive property; the helical structure
of the main chain can be transformed to random coil by addition of
trifluoroacetic acid to the THF solution which again switches back
to helical conformation by neutralization with triethylamine. It was
confirmed that the copolymerization of l-<b>1</b> and d-<b>1</b> obeyed the majority rule as supported by the
nonlinear correlation between the enantiomeric excess of monomer <b>1</b> with the CD intensities of the generated copolymers. Atomic
force microscope (AFM) and scanning electron microscope (SEM) studies
revealed poly-l-<b>1</b><sub>100</sub> self-assembled
into well-defined helical fibrils with distinct handedness
Air-Stable (Phenylbuta-1,3-diynyl)palladium(II) Complexes: Highly Active Initiators for Living Polymerization of Isocyanides
A family of air-stable (phenylbuta-1,3-diynyl)palladium(II)
complexes
were designed and prepared in a facile synthetic procedure. Their
structures were characterized by <sup>1</sup>H and <sup>13</sup>C
NMR, MS, and X-ray analysis. These Pd complexes were revealed to efficiently
initiate the polymerization of phenyl isocyanides in a living/controlled
chain growth manner, which led to the formation of poly(phenyl isocyanide)s
with controlled molecular weights and narrow molecular weight distributions. <sup>13</sup>C NMR analysis indicated the isolated poly(phenyl isocyanide)
was of high stereoregularity. The Pd unit at the end of the polymer
chain could undergo further copolymerization with phenyl isocyanide
monomers to give block copolymers. It was also found that incorporation
of an electron-donating group on the phenyl group of the Pd complex
could improve the catalytic activities. Furthermore, these Pd complexes
were tolerant to most organic solvents and applicable to a wide range
of isocyanide monomers including alkyl and phenyl isocyanides and
even phenyl isocyanide with bulky substituents at the ortho position
and diisocyanide monomers. Therefore, this polymerization system is
versatile in the preparation of well-defined polyisocyanides with
controlled sequence. Bi- and trifunctional Pd complexes with two and
three Pd units incorporated onto the same phenyl ring were designed
and synthesized. They were also able to initiate the living polymerization
of phenyl isocyanide to afford telechelic linear and star-shaped polyisocyanides
with controlled molecular weights and narrow molecular weight distributions