Pendant Carboxyl Research Articles

A Polyanionic Tartrate‐containing Temperature‐responsive Hydrogel

Thermogels, a class of hydrogels which show spontaneous sol-gel phase transition when warmed, are an important class of soft biomaterials. To date, however, most amphiphilic polymers that are able to form thermogels in aqueous solution are uncharged, and the influence of ionisable groups on thermogelation are largely unknown. Herein, we report the first example of a polyanionic amphiphilic multi-block copolymer, containing multiple pendant carboxylate groups, that can form transparent thermogels spontaneously when warmed up to physiological temperature. We demonstrate that introducing negative charges onto thermogelling polymers could significantly alter the properties of the micelles and thermogels formed. Furthermore, the polymer's polyanionic character provides new options for modulating the gel rheological properties, such as stiffness and gelation temperatures, through electrostatic interactions with different cations. We also demonstrated that the polyanionic thermogel allowed slower sustained release of a cationic model drug compound compared to an anionic one over 2 weeks. The findings from our study demonstrate exciting new possibilities for advanced biomedical applications using charged polyelectrolyte thermogel materials.

Toward Bifunctional Chelators for Thallium-201 for Use in Nuclear Medicine.

Auger electron therapy exploits the cytotoxicity of low-energy electrons emitted during radioactive decay that travel very short distances (typically <1 μm). 201Tl, with a half-life of 73 h, emits ∼37 Auger and other secondary electrons per decay and can be tracked in vivo as its gamma emissions enable SPECT imaging. Despite the useful nuclear properties of 201Tl, satisfactory bifunctional chelators to incorporate it into bioconjugates for molecular targeting have not been developed. H4pypa, H5decapa, H4neunpa-NH2, and H4noneunpa are multidentate N- and O-donor chelators that have previously been shown to have high affinity for 111In, 177Lu, and 89Zr. Herein, we report the synthesis and serum stability of [nat/201Tl]Tl3+ complexes with H4pypa, H5decapa, H4neunpa-NH2, and H4noneunpa. All ligands quickly and efficiently formed complexes with [201Tl]Tl3+ that gave simple single-peak radiochromatograms and showed greatly improved serum stability compared to DOTA and DTPA. [natTl]Tl-pypa was further characterized using nuclear magnetic resonance spectroscopy (NMR), mass spectroscopy (MS), and X-ray crystallography, showing evidence of the proton-dependent presence of a nine-coordinate complex and an eight-coordinate complex with a pendant carboxylic acid group. A prostate-specific membrane antigen (PSMA)-targeting bioconjugate of H4pypa was synthesized and radiolabeled. The uptake of [201Tl]Tl-pypa-PSMA in DU145 PSMA-positive and PSMA-negative prostate cancer cells was evaluated in vitro and showed evidence of bioreductive release of 201Tl and cellular uptake characteristic of unchelated [201Tl]TlCl. SPECT/CT imaging was used to probe the in vivo biodistribution and stability of [201Tl]Tl-pypa-PSMA. In healthy animals, [201Tl]Tl-pypa-PSMA did not show the myocardial uptake that is characteristic of unchelated 201Tl. In mice bearing DU145 PSMA-positive and PSMA-negative prostate cancer xenografts, the uptake of [201Tl]Tl-pypa-PSMA in DU145 PSMA-positive tumors was higher than that in DU145 PSMA-negative tumors but insufficient for useful tumor targeting. We conclude that H4pypa and related ligands represent an advance compared to conventional radiometal chelators such as DOTA and DTPA for Tl3+ chelation but do not resist dissociation for long periods in the biological environment due to vulnerability to reduction of Tl3+ and subsequent release of Tl+. However, this is the first report describing the incorporation of [201Tl]Tl3+ into a chelator–peptide bioconjugate and represents a significant advance in the field of 201Tl-based radiopharmaceuticals. The design of the next generation of chelators must include features to mitigate this susceptibility to bioreduction, which does not arise for other trivalent heavy radiometals.

Self-Matrix N-Doped Room Temperature Phosphorescent Carbon Dots Triggered by Visible and Ultraviolet Light Dual Modes.

The synthesis of room temperature phosphorescent carbon dots (RTP-CDs) without any matrix is important in various applications. In particular, RTP-CDs with dual modes of excitation are more interesting. Here, we successfully synthesized matrix-free carbonized polymer dots (CPDs) that can generate green RTP under visible and ultraviolet light dual-mode excitation. Using acrylic acid (AA) and ammonium oxalate as precursors, a simple one-pot hydrothermal method was selected to prepare AA-CPDs. Here, acrylic acid is easy to polymerize under high temperature and high pressure, which makes AA-CPDs form a dense cross-linked internal structure. Ammonium oxalate as a nitrogen source can form amino groups during the reaction, which reacts with a large number of pendant carboxyl groups on the polymer chains to further form a cross-linked structure. The carboxyl and amino groups on the surface of AA-CPDs are connected by intermolecular hydrogen bonds. These hydrogen bonds can provide space protection (isolation of oxygen) around the AA-CPDs phosphor, which can stably excite the triplet state. This self-matrix structure effectively inhibits the non-radiative transition by blocking the intramolecular motion of CPDs. Under the excitation of WLED and 365 nm ultraviolet light, AA-CPDs exhibit the phosphorescence emission at 464 nm and 476 nm, respectively. The naked-eye observation exceeds 5 s and 10 s, respectively, and the average lifetime at 365 nm excitation wavelength is as long as 412.03 ms. In addition, it successfully proved the potential application of AA-CPDs in image anti-counterfeiting.

Mechanical-robust and recyclable polyimide substrates coordinated with cyclic Ti-oxo cluster for flexible organic solar cells

With the rapid development of flexible optoelectronic devices, recyclability is highly desirable for alleviating resource waste and environmental pollution, but remains challenging. Here, a fully closed-loop recyclable crosslinked polyimide (RCPI) was fabricated via carboxyl ligand exchange between the CPI with pendent carboxyl groups and the cyclic Ti-oxo cluster (CTOC) with labile carboxyl ligands, which could be reconverted into reprocessable CPI and CTOC solution by pivalic acid. The RCPI-based embedded AgNWs@RCPI electrode shows comparable high conductivity, transparency and low roughness with ITO (indium tin oxide)/glass electrode, and meanwhile outstanding mechanical robustness. The related flexible organic solar cells (FOSCs) provided a high efficiency of 14.78% and maintained ~97% of the initial efficiency after 5000 bending cycles at a small bending radius of 1 mm. Moreover, the recyclability of the RCPI still retains after being manufactured into the FOSCs. This work provides a promising strategy for recyclable flexible optoelectronic devices.

Distinct Coordination Chemistry of Fe(III)-Based MRI Probes.

Contrast agents are used in approximately 40% of all magnetic resonance imaging (MRI) procedures to improve the quality of the images based on the distribution and dynamic clearance of the agent. To date, all clinically approved contrast agents are Gd(III) coordination complexes that serve to shorten the longitudinal (T1) and transverse (T2) proton relaxation times of water. Recent interest in replacing Gd with biologically relevant metal ions such as Mn or Fe has led to increased interest in the aqueous coordination chemistry of their complexes. In this Account, we focus on high-spin Fe(III) complexes that have been recently reported as MRI contrast agents or probes in our laboratory.The highly Lewis acidic Fe(III) center has distinct coordination chemistry in aqueous solutions, facilitating alternative strategies in the design of MRI probes. To illustrate this, we describe different classes of Fe(III) MRI probes with a focus on macrocyclic complexes and multinuclear complexes such as self-assembled metal organic polyhedra (MOP). Our initial efforts focused on macrocyclic complexes of Fe(III) in order to tune spin and oxidation states with the goal of stabilizing high-spin Fe(III) in reducing biological environments. Our probes feature six-coordinate Fe(III) complexes of 1,4,7-triazacyclononane with hydroxypropyl, phosphonate, or carboxylate pendant groups to produce Fe(III) complexes that shorten proton T1 times predominantly from second-sphere or outer-sphere interactions at neutral pH. Analogues with pentadentate macrocyclic ligands have an inner-sphere water that does not exchange rapidly on the NMR time scale, yet these complexes are effective relaxation agents. Fe(III) macrocyclic complexes in this class can be modified to modulate their biodistribution and pharmacokinetic clearance in mice. The goal of these studies is for the Fe(III) agents to clear as extracellular fluid agents and produce profiles similar to those of Gd agents. Finally, studies of multimeric Fe(III) complexes are of interest to produce probes that give large proton relaxivity. In this approach the two Fe(III) centers are connected through aryl linkers as demonstrated for several macrocyclic complexes. Even more tightly connected Fe(III) centers are produced in a Fe(III) self-assembled cage with relaxivity of 21 mM-1 s-1 at 4.7 T, 37 °C in the presence of serum albumin to which it is tightly bound. This cage enhances contrast of the vasculature as a blood pool agent and accumulates in tumors. Finally, we present our perspectives on the further development of Fe(III) complexes for various applications in MRI.

PH- and Thermo-Responsive Water-Soluble Smart Polyion Complex (PIC) Vesicle with Polyampholyte Shells.

A diblock copolymer (P(VBTAC/NaSS)17-b-PAPTAC50; P(VS)17A50) composed of amphoteric random copolymer, poly(vinylbenzyl trimethylammonium chloride-co-sodium p-styrensunfonate) (P(VBTAC/NaSS); P(VS)) and cationic poly(3-(acrylamidopropyl) trimethylammonium chloride) (PAPTAC; A) block, and poly(acrylic acid) (PAAc49) were prepared via a reversible addition−fragmentation chain transfer radical polymerization. Scrips V, S, and A represent VBTAC, NaSS, and PAPTAC blocks, respectively. Water-soluble polyion complex (PIC) vesicles were formed by mixing P(VS)17A50 and PAAc49 in water under basic conditions through electrostatic interactions between the cationic PAPTAC block and PAAc49 with the deprotonated pendant carboxylate anions. The PIC vesicle collapsed under an acidic medium because the pendant carboxylate anions in PAAc49 were protonated to delete the anionic charges. The PIC vesicle comprises an ionic PAPTAC/PAAc membrane coated with amphoteric random copolymer P(VS)17 shells. The PIC vesicle showed upper critical solution temperature (UCST) behavior in aqueous solutions because of the P(VS)17 shells. The pH- and thermo-responsive behavior of the PIC vesicle were studied using 1H NMR, static and dynamic light scattering, and percent transmittance measurements. When the ratio of the oppositely charged polymers in PAPTAC/PAAc was equal, the size and light scattering intensity of the PIC vesicle reached maximum values. The hydrophilic guest molecules can be encapsulated into the PIC vesicle at the base medium and released under acidic conditions. It is expected that the PIC vesicles will be applied as a smart drug delivery system.

Performance assessment of hybrid multiblock copolymers included with ionic liquid for fuel cell applications

To improve the proton conductivity and thermal stability of proton exchange membrane, hybrid poly (arylene ether) multiblock copolymers were synthesized by using 6F-bisphenol A monomer. The hydrophobic oligomers poly (arylene ether sulfone) containing 6F-bisphenol A with varying molecular weight were copolymerised with hydrophilic oligomer disulfonated poly (arylene ether ketone) containing pendant carboxylic acid group to prepare multiblock copolymers. For further enhancing the proton conductivity, ionic liquid is embedded into the synthesized multiblock copolymers to fabricate the hybrid multiblock membranes. The 1H NMR studies confirmed the synthesis of oligomers and multiblock copolymers whereas the FT-IR spectra revealed the interaction of ionic liquid with the multiblock copolymers. The proton conductivity of the membranes has also been examined at different temperatures and the activation energy required for the proton transport was calculated by using Arrhenius equation. At 30 °C, the maximum proton conductivity of 0.14 S/cm were shown by hybrid membrane (with 50% ionic liquid, 6FB1/I.L-50%), which is of 3.5 times greater than that of pristine 6FB1 membrane. Compared with pristine membranes, the hybrid membranes exhibit improved oxidative, thermal and mechanical stability. Moreover, the scanning electron microscopy (SEM) investigation depicts better phase separation in hybrid membranes than pristine membranes by forming ionic clusters. The membranes have been tested in H2/O2 fuel cell and their performance is compared with the state-of-art Nafion 117 membrane.

Co-delivery systems of paclitaxel prodrug for targeted synergistic therapy of breast cancer

This study reported a co-delivery system of paclitaxel (PTX) and doxorubicin (DOX) based on a functionalized poly(ϵ-caprolactone) (FC) conjugated with folate (FA) and PTX prodrug (FA-FC-PTX). PTX was conjugated to pendant carboxyl groups of FC by esterification, and FA was modified to PEG block of FC. The release behaviors of DOX and PTX from the micelles of FA-FC-PTX loaded with DOX (FA-FC-PTX/DOX) were obviously different. DOX was almost completely released in the initial 24 h, while a small amount of PTX was only released for 24 h, and continued to be released for 7 days. The cellular uptake results showed that FA-FC-PTX/DOX could be more effectively internalized by 4T1 cell than the non-folate drug-loaded micelles. In vitro cytotoxicity assays demonstrated that FA-FC-PTX/DOX revealed synergistic effect in inhibiting the proliferation of 4T1 mouse breast cancer cells. Cell apoptosis assays showed that FA-FC-PTX/DOX had the highest apoptosis rate in all drug formulations, indicating that it had high ability to induce cell apoptosis. Furthermore, it was found that FA-FC-PTX/DOX exhibited better inhibition effect on 4T1 tumor growth compared with free PTX/DOX combination or non-folate drug-loaded micelles and there was no obvious side effect on the 4T1 tumor-bearing mice. Thus, this work provides a promising drug co-delivery system for targeted therapy of breast cancer.

Copper(II) Complexes of Pyridine-2,6-dicarboxamide Ligands with High SOD Activity.

Copper(II) complexes of pyridine-based ligands functionalized with alanine (PydiAla) and tyrosine (PydiTyr) moieties have been synthesized as novel superoxide dismutase mimics. The complexes were characterized by pH-potentiometric, spectroscopic (UV-vis, circular dichroism, mass spectrometry, electron paramagnetic resonance spectroscopy), computational (DFT), and X-ray diffraction methods. Both ligands form high stability copper(II) complexes via the (Npy,N-,N-) donor set supported by the binding of the carboxylate pendant arms. Although the coordination mode is the same for the two systems, the tyrosine containing counterpart exhibits increased copper(II) binding affinity, which is most likely due to the presence of the aromatic moiety of the side chains. Both copper(II) complexes are capable of binding N-methylimidazole, and the formation of the corresponding ternary species was observed at physiological pH. The binary and ternary copper(II) complexes exhibit high SOD activity. The PydiTyr complex exhibits about 1 order of magnitude higher activity than the PydiAla complex. This is probably due to the presence of the phenolic OH group in the former species, which promotes the binding of the superoxide anion radical to the metal center. The results serve as a basis for designing highly efficient copper(II) mimics for medical and practical applications.

Dangling Carboxylic Group That Participates in O-O Bond Formation Reaction to Promote Water Oxidation Catalyzed by a Ruthenium Complex: Experimental Evidence of an Oxide Relay Pathway.

Two mononuclear ruthenium(II) complexes of the types [Ru(trpy)(HL1)(OH2)]2+ (1Aq) and [Ru(trpy)(L2-κ-N2O)] (2) [where trpy = 2,2':6',2″-terpyridine, HL1 = 2-(2-pyridyl)benzimidazole, H2L2 = 2-(pyridin-2-yl)-1H-benzo[d]imidazole-4-carboxylic acid] have been synthesized and thoroughly characterized by analytical and spectroscopic [UV-vis, NMR, high-resolution mass spectrometry, and IR] techniques. Complex 1Aq has been further characterized by X-ray crystallography. In an acidic aqueous medium (pH 1), complex 2 undergoes carboxylate/water exchange readily to form an aqua-ligated complex, [Ru(trpy)(H2L2-κ-N2)(OH2)]2+ (2Aq), having a dangling carboxylic group. This exchange phenomenon has been followed by IR, 1H NMR, and UV-vis spectroscopic techniques. Electrochemical analyses of 1Aq and 2Aq (Pourbaix diagram) suggest the generation of a formal RuV═O species that can potentially promote the oxidation of water. A comparative study of the water oxidation activity catalyzed by 1Aq and 2Aq is reported here to see the effect of a dangling carboxylic group in the catalytic performance. Complex 2Aq shows an enormously higher rate of reaction than 1Aq. The pendant carboxylic group in 2Aq participates in an intramolecular O-O bond formation reaction with the reactive formal RuV═O unit to form a percarboxylate intermediate and provides an electron-deficient carbon center where water nucleophilic attack takes place. The isotope labeling experiment using 18O-labeled water verifies the attack of water at the carbon center of the carboxylic group rather than a direct attack at the oxo of the formal RuV═O unit. The present work provides experimental evidence of the uncommon functionality of the carboxylic group, the oxide relay, in molecular water oxidation chemistry.

Open chain pseudopeptides as hydrogelators with reversible and dynamic responsiveness to pH, temperature and sonication as vehicles for controlled drug delivery

A new family of open chain-pseudopeptidic compounds displaying a pendant carboxylic group have been prepared with excellent yields. Their self-assembly has been studied under different conditions and in different media. Some of the compounds obtained have revealed to act as very efficient hydrogelators at low concentrations (CGC 1 mg mL−1). The resulting hydrogels show some interesting properties, including a high thermal stability, with the hydrogels maintaining their structure at temperatures above 65 °C, and their reversible dynamic sol–gel behavior being responsive to thermal and sonochemical inputs and to changes in the basic/acidic properties of the medium. Preliminary studies for controlled drug delivery have been carried out using a Franz Cell and employing a skin pig membrane, confirming that these Low Molecular Weight Gelators (LMWGs) can be appropriate vehicles for the controlled transdermal delivery of small-molecule drugs.

Self-Assembled Nanosized Vehicles from Amino Acid-Based Amphiphilic Polymers with Pendent Carboxyl Groups for Efficient Drug Delivery.

Developing safe and efficient delivery vehicles for chemotherapeutic drugs has been a long-standing demanding. Amino acid-based polymers are promising candidates to address this challenge due to their excellent biocompatibility and biodegradation. Herein, a series of well-defined amphiphilic block copolymers were prepared by PET-RAFT polymerization of N-acryloyl amino acid monomers. By altering monomer types and the block ratio of the copolymers, the copolymers self-assembled into nanostructures with various morphologies, including spheres, rod-like, fibers, and lamellae via hydrophobic and hydrogen bonding interactions. Significantly, the nanoparticles (NPs) assembled from amphiphilic block copolymers poly(N-acryloyl-valine)-b-poly(N-acryloyl-aspartic acid) (PV-b-PD) displayed an appealing cargo loading efficiency (21.8-32.6%) for a broad range of drugs (paclitaxel, doxorubicin (DOX), cisplatin, etc.) due to strong interactions. The DOX-loaded PV-b-PD NPs exhibited rapid cellular uptake (within 1 min) and a great therapeutic performance. These drug delivery systems provide new insights for regulating the controlled morphologies and improving the efficiency of drug delivery.

Polypeptide-based materials prepared by ring-opening polymerisation of anionic-based α-amino acid N-carboxyanhydrides: A platform for delivery of bioactive-compounds

Polymerisation of α-amino acid N-carboxyanhydrides (NCAs) is one of the most common techniques to prepare synthetic polypeptides. Of special interest are the NCAs derived from α-amino acids, L-aspartic acid and L-glutamic acid, since most investigations have been focused on their use to synthesise multiblock copolypeptides or hybrid synthetic polypeptide-polymers to design excipients suitable for delivery of bioactive compounds. This perspective highlights advantages of using L-aspartic acid and L-glutamic over other natural α-amino acids in that their pendant carboxyl group serves as a reactive handle for coupling a variety of reactive groups, and because the resulting polypeptides have the ability to adopt secondary structures. In addition, recent progress in the ring-opening polymerisation of NCAs will be discussed. Throughout, we provide representative examples that shed light on the NCAs polymerisation process, and we finally share our perspectives concerning the practical use of anionic α-amino acids as building blocks for future investigations.

One-step fabrication of dual functional Tb3+ coordinated polymeric micro/nano-structures for Cr(VI) adsorption and detection

Hexavalent chromium Cr(VI) has been considered as one of the most hazardous heavy metals because of its strong and persistent toxicity to the ecosystem and human beings. Herein, we have synthesized a double hydrophilic block co-polyarylene ether nitriles (abbreviated as dhPEN) bearing aromatic backbone as well as pendent carboxyl and sulfonate groups. Afterward, the synthesized dhPEN has been co-assembled with the lanthanide Tb3+ via a one-step solvent exchange protocol, leading to generation of Tb3+ coordinated dhPEN (Tb-dhPEN) micro/nano-structures that exhibit good adsorption capacity and detection sensitivity towards Cr(VI). More specifically, the direct self-assembly of dhPEN and Tb3+ in mixed H2O/DMF solvents resulted to Tb-dhPEN microparticles with lamellar structures, which exhibited a high Cr(VI) adsorption capacity approaching to 402 mg/g. The detailed characterization confirm that Cr(VI) is adsorbed and partially reduced to Cr(III) by the Tb-dhPEN microparticles via chemical interaction. Furthermore, the self-assembly of dhPEN with Tb3+ in the H2O/DMF mixed solvents containing NaOH contributed to the generation of spherical nanoparticles showing green emission at 545 nm, which can be selectively quenched by the Cr(VI), leading to the specific detection of trace concentration of Cr(VI) down to 0.12 nM as well as reliable determination of Cr(VI) presented in real environmental samples.

Use of pH-Active Catechol-Bearing Polymeric Nanogels with Glutathione-Responsive Dissociation to Codeliver Bortezomib and Doxorubicin for the Synergistic Therapy of Cancer.

Synergistic therapy holds promising potential in cancer treatment. Here, the inclusion of catechol moieties, a disulfide cross-linked structure, and pendent carboxyl into the network of polymeric nanogels with glutathione (GSH)-responsive dissociation and pH-sensitive release is first disclosed for the codelivery of doxorubicin (DOX) and bortezomib (BTZ) in synergistic cancer therapy. The pendent carboxyl groups and catechol moieties are exploited to absorb DOX through electrostatic interaction and conjugate BTZ through boronate ester, respectively. Both electrostatic interactions and boronate ester are stable at neutral or alkaline pH, while they are instable in an acidic environment to further recover the activities of BTZ and DOX. The polymeric nanogels possess a superior stability to prevent the premature leakage of drugs in a physiological environment, while their structure is destroyed in response to a typical endogenous stimulus (GSH) to unload drugs. The dissociation of the drug-loaded nanogels accelerates the intracellular release of DOX and BTZ and further enhances the therapeutic efficacy. In vitro and in vivo investigations revealed that the dual-drug loaded polymeric nanogels exhibited a strong ability to suppress tumor growth. This study thus proposes a new perspective on the production of multifunctional polymeric nanogels through the introduction of different functional monomers.

Thermal degradation behaviors of poly (arylene ether nitrile) bearing pendant carboxyl groups

Poly (arylene ether nitrile) (PAEN) bearing pendant carboxyl groups integrates the outstanding performances of special thermoplastics with the merit of solubility and has been extensively employed to prepare advanced composites for uses in dielectric and fluorescence field. This study firstly reported the thermal pyrolysis behavior of diphenolic acid (DBA)-based PAEN characterized by TG/DTG, TG-FTIR and TG-MS technique under non-oxidizing gaseous environment. It is found that PAEN showed third-order degradation mechanism: (i) Side chain degradation starts at 350–480 °C in the pentanoic acid moiety and CN groups, resulting in the main pyrolysis products of Ph-CH2-Ph-O-Ph or Ph-Ph-O-Ph by releasing CH4, H2O, HCN, CO, HCHO, CH3OH, CO2, HCOOH, C4H8. (ii) Main chain pyrolysis was caused by cleavages of CC and CO bond in backbone at 480–650 °C, mainly releasing aromatic compounds including C6H6, C7H8, C6H5OH, C6H5OCH3, etc. (iii) Carbonization happened over 650 °C and finally formed an extended aromatic array of graphite. The obtained results not only help our understanding for the identification, structural determination, and thermal resistance of PAEN materials, but also will guide molecular design of poly arylene ethers with higher thermal durability.

Aromatic block copolymer ligand sensitized lanthanide nanostructures as ratiometric fluorescence probe for determination of residual K2CO3 in super engineering thermoplastics

• An aromatic amphiphilic block copolymer named of D5S5 was synthesized. • D5S5 was self-assembled with Tb 3+ and Rhodamine B to obtain nanoprobe of Tb-D5S5/RB. • Tb-D5S5/RB exhibits pH dependent fluorescence emission in acid and basic solution. • Tb-D5S5/RB shows ratiometric enhanced fluorescence as the increased K 2 CO 3 content. • Tb-D5S5/RB nanoprobe is able to detect residual K 2 CO 3 in super-engineering polymer. The residual catalyst (K 2 CO 3 ) presented in the super engineering polyarylene ethers exerts side effects onto their processability and electrical properties. However, the sensitive and reliable analytical tools, that are able to detect residual K 2 CO 3 content in these high performance thermoplastics, are rarely reported. Herein, we firstly synthesized an aromatic amphiphilic block copolymer bearing pendent carboxyl and sulfonate groups (named as D5S5). Next, a lanthanide ions mediated solvent-exchange self-assembly was explored to fabricate fluorescent metallopolymeric nanospheres composed of D5S5 and Tb 3+ with strong green emission (named as Tb-D5S5). Then, the rhodamine B (RB) dyes were combined with the Tb-D5S5 to obtain the fluorescent probe of Tb-D5S5/RB, which exhibited a ratiometric fluorescence response to K 2 CO 3 . Specifically, the I 545 /I 585 (intensity ratio of two emission bands at 545 nm and 585 nm) of probe linearly increased with the increasing K + concentration of K 2 CO 3 in the range from 0.05 to 7.41 mM. Furthermore, the sensing mechanism of this probe towards K 2 CO 3 was revealed. Finally, the Tb-D5S5/RB probe was employed to determine the residual K 2 CO 3 in a super engineering polyarylene ether produced by an industrial plant, which showed 85.98 %–89.31 % recoveries of the benchmark results obtained from the inductively coupled plasma optical emission spectrometer (ICP-OES).

Design of Chiral NHC‐Carboxylates as Potential Ligands for Pd‐Catalyzed Enantioselective C−H Activation

AbstractDespite numerous efforts, the synthesis of scalemic carbo‐ and heterocycles through Pd0‐catalyzed C(sp3)−H activation employing chiral ancillary ligands or chiral bases is still limited. Inspired by the recently reported outstanding performance of IBiox‐type NHC ligands and bifunctional ligands in similar transformations, a new class of bifunctional NHC‐ligands bearing a pendant carboxylate group was designed. A library of 10 imidazolium‐carboxylic acids was obtained in five to six steps from enantiopure l‐tert‐leucinol. In addition, four well‐defined Pd(DMBPA)‐NHC palladacycles were synthesized in good to excellent yields from the corresponding imidazolium precursors. These complexes were tested in a prototypical C(sp3)−H arylation reaction, and the most active one afforded the indoline product in low yield but significant enantioselectivity. These new bifunctional NHCs could find broader applications in catalytic enantioselective transformations occurring under milder conditions.

Synthesis of Alkaline-soluble Triazine-based Poly(phenylene sulfide)s with Single/Double Pendant Carboxylic Acid Moieties and Their Application to Refractive Index Contrast Materials

Abstract The design, synthesis, and optical characterization of refractive-index-contrast (RIC) triazine-based poly(phenylene sulfide)s (PPSs) are investigated. Indeed, novel PPSs with two pendant groups, either tert-butyl (tBu) ester or carboxylic acid groups, at each monomer repeating unit (PPS-2E or PPS-2CA, respectively) were successfully synthesized. PPS-2CA showed high refractive index (n) values of 1.6964 (633 nm) and 1.6714 (940 nm) as well as high δn (increase in the n value by the deprotection of PPS-2E) values of +0.062 (633 nm) and +0.058 (940 nm).

Synthesis of DOTA-pyridine chelates for 64Cu coordination and radiolabeling of \u03b1MSH peptide

Background64Cu is one of the few radioisotopes that can be used for both imaging and therapy, enabling theranostics with identical chemical composition. Development of stable chelators is essential to harness the potential of this isotope, challenged by the presence of endogenous copper chelators. Pyridyl type chelators show good coordination ability with copper, prompting the present study of a series of chelates DOTA-xPy (x = 1–4) that sequentially substitute carboxyl moieties with pyridyl moieties on a DOTA backbone.ResultsWe found that the presence of pyridyl groups significantly increases 64Cu labeling conversion yield, with DOTA-2Py, −3Py and -4Py quantitatively complexing 64Cu at room temperature within 5 min (1 × 10− 4 M). [64Cu]Cu-DOTA-xPy (x = 2–4) exhibited good stability in human serum up to 24 h. When challenged with 1000 eq. of NOTA, no transmetallation was observed for all three 64Cu complexes. DOTA-xPy (x = 1–3) were conjugated to a cyclized α-melanocyte-stimulating hormone (αMSH) peptide by using one of the pendant carboxyl groups as a bifunctional handle. [64Cu]Cu-DOTA-xPy-αMSH retained good serum stability (> 96% in 24 h) and showed high binding affinity (Ki = 2.1–3.7 nM) towards the melanocortin 1 receptor.ConclusionDOTA-xPy (x = 1–3) are promising chelators for 64Cu. Further in vivo evaluation is necessary to assess the full potential of these chelators as a tool to enable further theranostic radiopharmaceutical development.