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

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    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

    No full text
    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

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    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

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    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

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    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

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    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

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    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

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    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

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    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

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    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
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