Zong-Quan Wu

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 (1)H and (13)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. (13)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.

Cobalt(II) coordination polymer exhibiting single-ion-magnet-type field-induced slow relaxation behavior.

A one-dimensional cobalt(II) coordination polymer, [Co(btm)2(SCN)2·H2O]n [btm = bis(1H-1,2,4-triazol-1-yl)methane], was synthesized and magnetically characterized. The isolated slightly distorted octahedral Co(II) ion displays field-induced slow relaxation with a big positive axial and a negative rhombic magnetic anisotropy (D = 93.9 cm(-1) and E = -10.5 cm(-1)), and the anisotropy energy barrier is 45.4 K.

Living polymerization of arylisocyanide initiated by the phenylethynyl palladium(II) complex

A family of air-stable phenylethynyl palladium complexes was unexpectedly found to initiate the polymerization of phenyl isocyanide in a living/controlled chain growth manner, affording well-defined, stereoregular poly(phenyl isocyanide)s in high yield with controlled molecular weights and narrow molecular weight distributions.

Versatile pH-response Micelles with High Cell-Penetrating Helical Diblock Copolymers for Photoacoustic Imaging Guided Synergistic Chemo-Photothermal Therapy

With high optical absorption efficiency, near infrared (NIR) dyes have been proposed as theranostic agents for fluorescence imaging, photoacoustic imaging (PAI), and photothermal therapy (PTT). However, inherent hydrophobicity and short circulation time of small molecule hinder the further biomedical application. Herein smart amphiphilic copolymer was synthesized containing IR780/camptothecin@poly(ε-caprolactone) (IR780/CPT@PCL) as core, helical poly(phenyl isocyanide) (PPI) blocks as shell with the pH-responsive rhodamine B (RhB) moieties in the core-shell interface. With hydrophilic helical PPI coronas, these micelles present significantly enhanced cell-penetrating capacity that plays a key role in facilitating intracellular delivery of various cargos. By encapsulating CPT and IR780 molecules, the multifunctional self-assemble probe has huge potential to realize functional cooperativity and adaptability for cancer diagnosis and therapy. The in vitro and in vivo experimental results demonstrate that the pH-triggered fluorescent responsiveness and strong acoustic generation permit them efficient fluorescent and PA signal sensing for cancer diagnosis. Moreover, with 808 nm laser irradiation, the generated heat significantly improves the drug release from PCL core, leading to synergetic chemo-photothermal therapy and decreases tumor recurrence rates in mice. Overall, the biocompatible multifunctional micelles with these combined advantages can potentially be utilized for PAI guided disease diagnosis and tumor ablation.

One pot synthesis of poly(3-hexylthiophene)-block-poly(hexadecyloxylallene) by sequential monomer addition.

A series of poly(3-hexylthiophene)-b-poly(hexadecyloxylallene) copolymers has been synthesized in one pot via sequential monomer addition by using Ni(dppp)Cl2 as a single catalyst. The copolymerization has been revealed to proceed by a controlled chain extension mechanism and the block copolymer can self-assemble into a well-defined supramolecular structure in solution and exhibit microphase separation in the solid state.

Polypeptide-b-Poly(Phenyl Isocyanide) Hybrid Rod-Rod Copolymers: One-Pot Synthesis, Self-Assembly, and Cell Imaging

Hybrid rod-rod diblock copolymers, poly(γ-benzyl L-glutamate)-poly(4-cyano-benzoic acid 2-isopropyl-5-methyl-cyclohexyl ester) (PBLG-PPI), with determined chirality are facilely synthesized through sequential copolymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and phenyl isocyanide monomers bearing chiral menthyl pendants using a Ni(cod)(bpy) complex as the catalyst in one-pot. Circular dichroism and absorption spectra reveal that each block of the block copolymers possesses a stable helical conformation with controlled helicity in solution due to the induction of chiral pendants. The two diastereomeric polymers self-assemble into helical nanofibrils with opposite handedness due to the different chiral induction of the L- and D-menthyl pendants, confirmed by transmission electron microscopy (TEM). Deprotection of the benzyl groups of the PBLG segment affords biocompatible amphiphilic diblock copolymers, poly(L-glutamic acid)-poly(4-cyano-benzoic acid 2-isopropyl-5-methyl-cyclohexyl ester) (PLGA-PPI), that can self-assemble into well-defined micelles by cosolvent induced aggregation. Very interestingly, a chiral rhodamine chromophores RhB(D) can be selectively encapsulated into the chiral polymeric micelles, which is efficiently internalized into living cells when directly monitored with a confocal microscope. This contribution will be useful for developing novel rod-rod biocompatible hybrid block copolymers with a controlled helicity, and may also provide unique chiral materials for potential bio-medical applications.

Facile synthesis of stereoregular helical poly(phenyl isocyanide)s and poly(phenyl isocyanide)-block-poly(L-lactic acid) copolymers using alkylethynylpalladium(II) complexes as initiators

The development of novel synthetic methods for the facile preparation of well-defined stereoregular helical polyisocyanides and their block copolymers in a living/controlled fashion is of great interest. In this contribution, a family of air-stable alkylethynyl Pd(II) complexes was unexpectedly found to promote the living polymerization of phenyl isocyanide, affording poly(phenyl isocyanide)s with controlled molecular weights, narrow molecular weight distributions and high stereoregularity. Interestingly, such alkylethynyl Pd(II) complexes exhibit very high helix-sense-selectivity in the living polymerization of an optically active phenyl isocyanide bearing an L-alanine pendant with a long decyl chain, and a single handed helical poly(phenyl isocyanide) with controlled helical sense was selectively produced. Moreover, a Pd(II) complex bearing a hydroxyl group can initiate the living polymerization of both phenyl isocyanide and L-lactide in one-pot, leading to the formation of well-defined poly(phenyl isocyanide)-b-poly(L-lactic acid) copolymers in high yields with controlled molecular weights and tunable compositions. Although the two monomers were polymerized via distinct mechanisms, the block copolymerization was revealed to proceed under living/controlled manners.

Fabrication of SERS-active conjugated copolymers/gold nanoparticles composite films by interface-directed assembly

We report a new type of functional composite films by taking advantage of the interface-directed assembly between thiol groups functionalized poly(4-isocyano benzoic acid⋯pyridine-4-thiol)-b-poly(3-hexylthiophene) (PPI(–SH)-b-P3HT) conjugated copolymers and gold nanoparticles (Au NPs) at the chloroform/water interface. The PPI(–SH)-b-P3HT copolymers were synthesized through hydrogen bonding induced micellization and subsequent thiol–disulfide exchange reaction. Transmission electron microscopic (TEM) and atomic force microscopy (AFM) observations showed the film was uniform on a large scale and the integrity of surface morphology was not affected by the Au NPs concentration. Interestingly, the film substrate not only exhibited a strongly Au NPs concentration dependent surface-enhanced Raman scattering (SERS) activity but also allowed detection of model molecule, IR-792 perchlorate (IR-792), in the SERS measurement. This proof-of-concept suggests the interfacial assembly route is effective in integrating the properties of organic polymers and inorganic nanoparticles, and for further application.

Multi-responsive behavior of highly water-soluble poly(3-hexylthiophene)-block-poly(phenyl isocyanide) block copolymers

The design and synthesis of highly water-soluble conjugated block copolymers with multi-responsive properties are of great interest due to the copolymers’ potential as solution processable semiconductor materials. Herein, we report a one-pot synthesis of well-defined block copolymers containing conjugated poly(3-hexylthiophene) (P3HT) and poly(phenyl isocyanide) (PPI) bearing hydrophilic tri(ethylene glycol) monomethyl ether chains. These block copolymers have good solubility in water and exhibit excellent thermoresponsive behavior. The lower critical solution temperature (LCST) in water can be facilely tuned through varying the concentration or polymer composition. Moreover, the optical properties of the block copolymer are dependent on the solvents used owing to the distinct self-assembled structures. In CHCl3, the P3HT-b-PPI block copolymer exhibits pH-responsive behavior with the emission color changing between orange and blue upon alternate additions of trifluoroacetic acid and triethylamine. In addition, such block copolymers are revealed to be good materials for live cell imaging.

Field-induced Slow Magnetic Relaxation In A Hydrogen-Bonding Linked Co(II) 1D Supramolecular Coordination Polymer

We have investigated the dynamic behaviour of the magnetization of a hydrogen-bonding linked Co(II) 1D supramolecular coordination polymer. In the structure, two different mononuclear Co(II) species are linked by O–H···N hydrogen bonding through coordinated H2O and . Field-induced slow magnetic relaxation effect is observed and the anisotropy energy barrier is 33 K. Ab initio calculations reveal that Co(II) ion in [Co(bpm)2(N3)2] species is uniaxial anisotropic with a negative axial zero-field splitting parameter of D = − 82.4 cm− 1. The Co(II) ion in [Co(bpm)2(H2O)2]2+ species, however, is easy-plane anisotropic with a positive D and negative E value (D = 46.3 cm− 1, E = − 7.8 cm− 1). This is an interesting complex in which slow magnetic relaxation stems from the combination contribution of uniaxial anisotropy and easy plane anisotropy.