Reactive Terminal Groups Research Articles

Green Fluorescent Diamino‐Terephthalonitriles with Reactive Terminal Groups Towards Synthesis of Value‐Added Fluorophores

AbstractWe report synthesis of a library of diamino‐terephthalonitrile based single‐benzene fluorophores (SBFs). These SBFs contain a reactive terminal linker group. They open up the possibility of marrying their excellent fluorescent property with various biogenic units, leading to value‐added SBFs. The solvatofluorochromism behavior of these newly synthesized SBFs was also studied. The emission enhances and blue‐shifts in case of non‐polar solvents and vice versa in the polar solvents, implying the environmental sensitivity of these fluorophores. Photostability test was also done to test for the stability of the emission of these fluorophores with time and the fluorophores were found to be stable. We also observed time‐dependent fluorescence enhancement of one of our SBFs in presence of reactive biogenic amines. Overall, the generation of these novel molecules opens up new opportunities towards bioconjugated fluorophores.

Synthetic Approaches towards Peptide‐Conjugates of Pt(II) Compounds with an (O,S) Chelating Moiety

AbstractMetal‐containing peptide (bio−)conjugates have received continuous interest due to their enormous potential for bioinorganic and medicinal research. In many bioconjugates the chemical inertness of the metal‐containing units facilitates synthesis e. g. by copper‐catalyzed alkyne−azide cycloaddition or the formation of peptide bonds. However, when the metal complex contains labile ligands, which are often critical to their biological activity, the synthetic proceeding requires careful planning. Here, we report on the synthesis of a set of peptide bioconjugates with a platinum(II) core, coordinated through widely variable (O,S) chelating β‐hydroxydithiocinnamic ester and two monodentate ligands. We have evaluated the synthetic applicability of metal−peptide bioconjugation techniques between the model peptide Leu5−enkephalin and differently functionalized (O,S)Pt units. Within this, the type and position of anchor used at the β‐hydroxydithiocinnamic unit proved to be crucial for success, but equally important was the synthetic order of conjugation and complexation. In this work, synthetic approaches for the linkage of metal complexes that are coordinated by functionalized ligands towards peptides were explored. Two general methods to link the studied (O,S)Pt pharmacophore to the model peptide, Leu5−enkephalin, have been applied, namely the most prominent “click” reaction, CuAAC, and the linking via amide bonds. Overall, it could be shown that the structural motif of the (O,S)Pt compounds presented here offers multiple possibilities of derivatization, so that bioconjugation towards peptides can be made possible. Depending on the demands made on the resulting metal bioconjugate, both the dithioester and the aromatic unit of β‐hydroxydithiocinnamic esters can be used as anchor for peptides. However, from our results here, it can be concluded that anchoring at the aromatic subsite seems preferable from a synthetic point of view as the spatial distance of the reactive terminal functional group (alkyne or azide) to the metal center may avoid intramolecular reactions. Also, for using azide−alkyne click chemistry as a conjugation strategy, the (O,S) unit should contain the azide function and not the alkyne function, as triple bond hydration may occur. Classical amide‐bond conjugation also proved to be a suitable method in our hands when performed in solution. A coupling of the β‐hydroxydithiocinnamic unit to resin‐bound peptide would not be possible due to the typically harsh cleavage conditions.

Enhancement of the stability window of PEO for high voltage all-solid-state lithium batteries

Polyethylene oxide (PEO), one of the leading polymer electrolytes recommended against the safety concerns of liquid electrolytes, is unsuitable for high potential positive electrodes (e.g. LiNixMnyCozO2) needed to meet the increasing energy demand. Herein PEO main chain has been stabilized by modifying its (-OH) reactive terminal group. Modification of the reactive (-OH) group with (-OCH3) and (−CN) terminal groups exhibit a remarkable increase in the ionic conductivity at ambient temperature (4.52 × 10−4 S cm−1). In addition, electrochemical stability window (ESW) has been expanded (>4.18 V). The modified gel polymer electrolyte (GPE) has exhibited 150 mAh g−1 discharge capacity and has retained 92% of its capacity for 50 cycles in charge-discharge tests. Instead of increasing the ESW with inorganic additives, modification of PEO's (-OH) reactive terminal groups and making the PEO main chain a stable matrix can be a more permanent solution/strategy in the first instance. Moreover, developed solid electrolyte promise stability, safety and flexibility, making their utilization possible even with complex geometry batteries with high energy density.

Flexible and alternately layered high electrochemical active electrode based on MXene, carboxymethylcellulose, and carbon nanotube for asymmetric micro-supercapacitors

Recent studies have shown that Ti-based MXene has great potential for electrochemical energy storage applications, including Li-ion batteries and micro-supercapacitors. However, self-stacking and weak interlayer interactions lead to poor electrochemical properties. Herein, a simple one-step vacuum filtration method was used to prepare a MXene/carboxymethylcellulose/carbon nanotube (Ti3C2Tx/CMC/CNT) hybrid membrane. Due to the unique adhesion and flexibility of CMC, it can be interwoven with CNT to form an interconnected mesh structure, which on the one hand mitigates the self-aggregation of CNT, and on the other hand, the CNT entangled on the surface of CMC imparts its electrical conductivity. Moreover, the –OH of CMC can form hydrogen bonds with the reactive terminal groups (-O, –OH, -F) of Ti3C2Tx, resulting in the tight anchoring of CMC and CNT to Ti3C2Tx nanosheet layers and bridging adjacent Ti3C2Tx nanosheets to form a complete conductive pathway. As a result, the mechanical property test indicates that the Ti3C2Tx/CMC/CNT hybrid film could achieve a maximum tensile strength of 64.9 MPa. Furthermore, an asymmetric micro-supercapacitor (MSC) using Ti3C2Tx/CMC/CNT as the cathode and reduced graphene oxide/carboxymethylcellulose/polypyrrole (RGO/CMC/PPy) as the anode was fabricated, which exhibited a high energy density of 258.8 μWh cm−2 at a power density of 750 μW cm−2, and an ultra-long cycle life (93.2% capacitance retention after 15,000 GCD cycles). The simple and scalable preparation process makes this MSC device very promising for commercial electronics applications.

Monoribbed‐Functionalized Macrobicyclic Iron(II) Complexes Decorated with Terminal Reactive and Vector Groups: Synthetic Strategy, Chemical Transformations and Structural Characterization

Comprehensive SummaryGeneral and straightforward synthetic strategy towards the iron(II) clathrochelates with functionalizing substituents in their apical capping and one of the three chelate ribbed fragments was developed. Their hexachloroclathrochelate precursors were prepared by the direct template condensation of dichloroglyoxime with a suitable boronic acid on the Fe2+ ion as a matrix and underwent a stepwise nucleophilic substitution with S2‐, N2‐ or O2‐bis‐nucleophiles, forming the alicyclic or aromatic N2‐, S2‐ or O2‐six‐membered fragments. Depending on the reaction conditions and precursor‐to‐dinucleophile molar ratios, iron(II) clathrochelates with one (S, O and N), two (S, O and N) or three (S and O) X2‐six‐membered ribbed substituent(s) were obtained. Their reactivity substantially decreases in a row: Cl6‐Cage > Cl4X2‐Cage (where X = S, O or, especially, N) > Cl2X4‐Cage (where X = S or O). The reactive monoribbed‐functionalized clathrochelates underwent further chemical transformations giving the target macrobicyclic complexes with terminal vector groups. As follows from the single crystal XRD data, their FeN6‐coordination polyhedra possess the geometry intermediate between a trigonal prism and a trigonal antiprism (φ = 21.3°—25.20°). Fe—N distances vary from 1.887(6) to 1.933(8) Å. Their 3D‐molecules, the hydrophobic–hydrophilic balance in which can be tuned using a ribbed functionalization, form in the crystals the intermolecular specific halogen bonds and/or hydrophobic interactions.

Hybrid iron(II) phthalocyaninatoclathrochelates with a terminal reactive vinyl group and their organo-inorganic polymeric derivatives: synthetic approaches, X-ray structures and copolymerization with styrene.

Hybrid metallo(IV)phthalocyaninate-capped tris-dioximate iron(II) complexes (termed as "phthalocyaninatoclathrochelates") with non-equivalent apical fragments and functionalized with one terminal reactive vinyl group were prepared for the first time using three different synthetic approaches: (i) transmetallation (capping group exchange) of the appropriate labile boron,antimony-capped cage precursors, (ii) capping of the initially isolated reactive semiclathrochelate intermediate, and (iii) direct one-pot template condensation of their ligand synthons on the iron(II) ion as a matrix. The obtained polytopic cage complexes were characterized using elemental analysis, 1H NMR, MALDI-TOF MS and UV-vis spectra, and the single-crystal X-ray diffraction experiments. One of the obtained vinyl-terminated iron(II) phthalocyaninatoclathrochelates and its semiclathrochelate precursor were tested as monomers in a copolymerization reaction with styrene as the main component. These vinyl-terminated (semi)clathrochelate iron(II) complexes were found to be successfully copolymerized with this industrially important monomer, affording the intensely colored copolymer products. Because of a low solubility of the tested zirconium(IV) phthalocyaninate-capped tris-nioximate monomer in styrene as a solvent, a molar ratio of 1 : 500 was used. The obtained copolymer products and the kinetics of their formation were studied using GPC, FTIR, UV-vis, TGA and DSC methods. Even at such a low concentration of the Fe,Zr-binuclear metallocomplex component, an increase in the rate of the UV-light degradation of the organo-inorganic products, as well as in their thermal stability, was observed.

Synthesis and reactivity of the apically functionalized (pseudo)macrobicyclic iron(ii) tris-dioximates and their hybrid phthalocyaninatoclathrochelate derivatives comprising reactive and vector terminal groups

Iron(ii) phthalocyaninatoclathrochelates functionalized with terminal reactive formyl group were prepared. Their post-synthetic functionalization gave those with vector pharmacophoric fragment.

Low-cost, ubiquitous biomolecule as a strength enhancer for cement mortars

This study explores a bioinspired, low-cost, and ubiquitous biomolecule – tannic acid (TA) – as a small-dose molecular-scale admixture to modify the nano- and micro-structures of the major hydration product of ordinary Portland cement (OPC) (e.g., calcium silicate hydrate (C-S-H)) so that the performance and eco-efficiency of the concrete can be significantly enhanced. With abundant reactive terminal phenolic hydroxyl groups, TA can cross-link macromolecular sites through multiple interactions, including hydrogen and ionic bonds and hydrophobic interactions. Therefore, TA can be used to manipulate the structure of C-S-H gel, and to fundamentally modify the properties of concrete. Testing results show that adding TA could reduce the total porosity of the mortar by up to 31%. Particularly, the capillary pores with size within 10 nm – 50 nm were significantly reduced. Both the packing densities and elastic modulus of the hydration products were also increased by adding TA, as indicated by nanoindentation testing. As a result, much better mechanical performance is achieved. Furthermore, finite element simulation revealed that more uniform distribution of stress is achieved by the presence of TA. This study broadens the application of bio-based molecules in concrete, bringing new possibilities of reactivity and offering higher specificity for interaction with targeted phases. Compared with existing petroleum-based admixtures, bio-based molecules enjoy many advantages, such as abundant, renewable, safe, yet low-cost.

Experimental investigation on the thermal resistance of thermotropic aromatic oligoesters

Synthesis and characterization of liquid crystalline polymers based on 4-hydroxybenzoic acid, aromatic dibasic acids, and aromatic diols via a high-temperature polycondensation are described. FT-IR spectroscopy was employed to evaluate a molecular weight of the samples that can be considered as oligoesters. The mesophase existence ranges of the samples were estimated by means of DSC and optical polarizing microscopy. Liquid crystalline oligoesters offer excellent thermal (T0 = 250-373 °C) properties. The macromolecules obtained contain reactive terminal groups and retain the ability to grow at elevated temperatures.

Self-assembling behaviour of chiral calamitic monoacrylates targeted for polymer stabilisation of polar smectic phases in chiral liquid crystals

The stabilisation and control of synclinic and anticlinic chiral liquid crystalline phases remain an actual and highlighted task. This work presents the design and mesomorphic properties of new chiral calamitic reactive mesogens, monoacrylates, based on biphenyl benzoate and phenyl biphenyl-4-carboxylate cores with reactive terminal groups placed far from the chiral chain. The compound's structures, compatible with the components of modern ferroelectric and antiferroelectric liquid crystalline mixtures, are confirmed by mass spectrometry (electron ionization) analysis and proton/carbon nuclear magnetic resonance. All the reactive mesogens possess the self-assembling, i.e. liquid crystalline behaviour with high tendency to create smectic phases in a broad temperature range, which was confirmed by a polarizing optical microscopy, differential scanning calorimetry and broad-band dielectric spectroscopy. Doping of advanced multicomponent mixtures possessing the chiral smectic phases by the designed monoacrylates with further cross-linking procedure, can be an effective and functional tool for stabilising ferroelectric and antiferroelectric phases in various states and hence, can allow the symmetrisation of the switching times in the modes employed surface stabilised geometry; this is a very highlighted task for optoelectronics. Moreover, an evident considerable tendency for thermal polymerisation of specific reactive mesogens can reduce the drawbacks of polymer stabilisation.

Folding fluorescent probes for self-reporting transesterification in dynamic polymer networks.

Dynamic exchange reactions in covalent adaptable networks (CANs) are difficult to probe directly via various macroscopic mechanical methods. Herein, we report a fluorescent strategy for directly reporting the dynamic bond exchange in transesterification-based CANs by using folding molecular probes. The folding probes (PDI-dimers) consist of two perylene diimide (PDI) cores, a spacer of dynamic esters between the two PDI cores, and reactive terminal groups. During transesterification in CANs, the PDI-dimers unfold their PDI excimers to show a sharp fluorescent color change from orange to bright yellow. This visual strategy is demonstrated by a crosslinked thiol-Michael network (TMN) and poly(4-hydroxybutyl acrylate) network (PHBA). The dynamic behaviors like stress relaxation and self-stiffening in these CANs can be directly read out via the change of fluorescent color. This method can provide quantitative information and show spatiotemporal resolution and therefore, can be applied to probe various dynamic chain exchange mechanisms in crosslinked materials.

Research progress on the biomimetic remineralization of hard tooth tissues based on polyamide-amine dendrimer

Polyamide-amine (PAMAM) dendrimer, a new hyperbranched macromolecular polymer, is considered an "artificial protein" by many scholars on account of its excellent chemical and biological characteristics. PAMAM has internal cavities and a large number of reactive terminal groups. These structures allow the polymer to be used as a bionic macromoleculethat could simulate the biomimetic mineralization of the natural organic matrix on the surface of tooth tissue. Specifically, PAMAM can beused as an organic template to regulate mineral nucleation and crystal growth; thus, the polymerisa more ideal dental restoration material than traditional allogenic materials. This article reviews research progress on thePAMAM-induced biomimetic mineralization of hard tooth tissues.

Semi‐Interpenetrating Polymer Electrolyte as a Coating Layer Constructed on Polyphenylene Sulfide Nonwoven to Afford Superior Stability and Performance for Lithium‐Ion Batteries

AbstractHigh power lithium‐ion battery (LIB) puts forward higher requirements for separator. In this study, a new composite separator (SIPN/PPS) with superior stability and improved electrochemical performance was fabricated by the construction of semi‐interpenetrating polymer network (SIPN) on polyphenylene sulfide (PPS) nonwoven substrate. In SIPN, branched polyethyleneimine (PEI) was selected as crosslinking points due to multiple reactive terminal groups −NH2. Meanwhile, PEI owned irregular topology structure, which would be beneficial to interrupt the crystallization of polymer matrix and increase electrolyte storage by swelling. Characterization results show that this designed composite separator can exhibit higher porosity, improved electrolyte wettability, enhanced electrolyte uptake and excellent electrochemical performance, thus endowing battery with superior discharge capacity even at 3 C. In addition, the introduction of SIPN is confirmed to increase mechanical strength more obviously than that of single cross‐linked network reported in previous study. Meanwhile, anode current begins to be detected for SIPN/PPS composite separator under higher applied voltage (4.6 V vs Li+/Li), indicating its broader electrochemical window. Moreover, SIPN/PPS composite separator is displayed satisfactory cycling stability with higher discharge capacity retention ratio (85.3 %). Consequently, this contribution opens a new avenue for separator applied in high power LIB.

Ready-to-Use Germanium Surfaces for the Development of FTIR-Based Biosensors for Proteins.

Germanium is particularly suitable for the design of FTIR-based biosensors for proteins. The grafting of stable and thin organic layers on germanium surfaces remains, however, challenging. To tackle this problem, we developed a calix[4]arene-tetradiazonium salt decorated with four oligo(ethylene glycol) chains and a terminal reactive carboxyl group. This versatile molecular platform was covalently grafted on germanium surfaces to yield robust ready-to-use surfaces for biosensing applications. The grafted calixarene monolayer prevents nonspecific adsorption of proteins while allowing bioconjugation with biomolecules such as bovine serum albumin (BSA) or biotin. It is shown that the native form of the investigated proteins was maintained upon immobilization. As a proof of concept, the resulting calix[4]arene-based germanium biosensors were used through a combination of ATR-FTIR spectroscopy and fluorescence microscopy for the selective detection of streptavidin from a complex medium. This study opens real possibilities for the development of sensitive and selective FTIR-based biosensors devoted to the detection of proteins.

Heat-Resistant Polymer Materials Based on Liquid Crystal Compounds

Data on heat-resistant linear and crosslinked polymer materials containing mesogenic groups in their structure have been systematized. Principles of the macromolecular design of thermoplastic liquid-crystal (LC) polymers providing high performance characteristics and their relationship with the supermolecular organization and processing conditions have been discussed. Methods for synthesizing LC precursors with reactive terminal groups cured to form three-dimensional LC networks have been discussed; the effect of the chemical nature of the terminal groups on the thermal stability of the resulting material has been shown.

Evaluation of PSMA-Targeted PAMAM Dendrimer Nanoparticles in a Murine Model of Prostate Cancer.

The prostate-specific membrane antigen (PSMA) is a validated target for detection and management of prostate cancer (PC). It has also been utilized for targeted drug delivery through antibody-drug conjugates and polymeric micelles. Polyamidoamine (PAMAM) dendrimers are emerging as a versatile platform in a number of biomedical applications due to their unique physicochemical properties, including small size, large number of reactive terminal groups, bulky interior void volume, and biocompatibility. Here, we report the synthesis of generation 4 PSMA-targeted PAMAM dendrimers [G4(MP-KEU)] and evaluation of their targeting properties in vitro and in vivo using an experimental model of PC. A facile, one-pot synthesis gave nearly neutral nanoparticles with a narrow size distribution of 5 nm in diameter and a molecular weight of 27.3 kDa. They exhibited in vitro target specificity with a dissociation constant ( Kd) of 0.32 ± 0.23 μm and preferential accumulation in PSMA+ PC3 PIP tumors versus isogenic PSMA- PC3 flu tumors. Positron emission tomography-computed tomography imaging and ex vivo biodistribution studies of dendrimers radiolabeled with 64Cu, [64Cu]G4(MP-KEU), demonstrated high accumulation in PSMA+ PC3 PIP tumors at 24 h post-injection (45.83 ± 20.09% injected dose per gram of tissue, %ID/g), demonstrating a PSMA+ PC3 PIP/PSMA- PC3 flu ratio of 7.65 ± 3.35. Specific accumulation of G4(MP-KEU) and [64Cu]G4(MP-KEU) in PSMA+ PC3 PIP tumors was inhibited by the known small-molecule PSMA inhibitor, ZJ-43. On the contrary, G4(Ctrl), control dendrimers without PSMA-targeting moieties, showed comparable low accumulation of ∼1%ID/g in tumors irrespective of PSMA expression, further confirming PSMA+ tumor-specific uptake of G4(MP-KEU). These results suggest that G4(MP-KEU) may represent a suitable scaffold by which to target PSMA-expressing tissues with imaging and therapeutic agents.

Free-standing polydimethylsiloxane-based cross-linked network solid polymer electrolytes for future lithium ion battery applications

A series of cross-linked network solid polymer electrolytes based on dual end-functionalized polydimethylsiloxane bearing reactive thiol terminal groups with poly(ethylene glycol) diglycidyl ether and pentaerythritol tetrakis(3-mercaptopropionate) have been synthesized and characterized. The obtained results can be briefed as: ionic conductivity in the range of 1.5 × 10−6 S cm−1 at room temperature to 1.6 × 10−4 S cm−1 at 90 °C, lithium ion transference number ranged from 0.15 to 0.20, electrochemical window up to 5.3 V (vs. Li+/Li), thermal resistance (Td5ca. 254.5 °C), and tensile strength (ca. 1.6 MPa at max.). The interplay taking place between structure and physico-electrochemical properties of in these systems based on merits of poly(ethylene glycol) moieties as high solvation matrix for Li+ ions flexible along with smooth solid support from polydimethylsiloxane allow the tailoring of the design of polymer electrolytes for future all-solid-state lithium batteries.

Grafting polymerization of glycidyl methacrylate onto capillary-channeled polymer (C-CP) fibers as a ligand binding platform: Applications in immobilized metal-ion affinity chromatography (IMAC) protein separations

Immobilized metal-ion affinity chromatography (IMAC) is a valuable method for preparative and analytical-scale protein separations. Nylon 6 capillary-channeled polymer (C-CP) fibers were grafted with glycidyl methacrylate (GMA) as a monomer with ceric ammonium nitrate (in dilute nitric acid) used as the initiator. The polymerization reaction occurs rapidly (15 min) in a residential microwave. Iminodiacetic acid (IDA) is then attached to the grafted GMA polymers by reacting with the reactive terminal epoxide groups. Different parameters regarding the grafting time, initiator concentration and conversion time were investigated to find the optimal conditions for the entire modification process. The resulting nylon-IDA fibers were characterized by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM). The resulting carboxyl density and copper binding capacity were determined to be 612 ± 21 μmol g−1 and 375 ± 12 μmol g−1, respectively. When charged with Cu2+ ions and packed in a column format, the nylon-IDA fibers can be applied as an IMAC stationary phase for the separation of histidine rich proteins. The performance of this novel phase was evaluated through the separation of a mixture of model proteins (cytochrome C, α-chymotrypsinogen A and lysozyme) and a recombinant histidine-tagged protein (his-tagged ubiquitin). Despite multi-step modifications, columns of the modified fibers still maintain the anticipated high levels of throughput and efficiency, with binding capacities of 6.89 ± 0.56 mg lysozyme g−1 fiber and 6.32 ± 0.12 mg His-tagged ubiquitin g−1 fiber.

Identification of multi-crosslinked species by mass spectrometry

A search for multiple crosslinking reaction products was conducted using processed raw data of the protein SALBIII obtained by LC/MS-MS. In parallel, new compounds containing three reactive terminal groups were used with myoglobin and cytochrome c to evaluate the formation of multiple crosslinked species.

Single-Polymer-Single-Cargo Strategy Packages Hydrophobic Fluorophores in Aqueous Solution with Retention of Inherent Brightness.

A strategy for encapsulating hydrophobic organic entities in aqueous solution has been developed through use of a self-assembling heterotelechelic amphiphilic random copolymer. The polymer (∼40 kDa), prepared by living radical polymerization, contains orthogonally reactive terminal groups and pendant hydrophobic (dodecyl), nonionic hydrophilic (PEG9), and ionic hydrophilic (sulfonate-terminated) groups. Covalent conjugation of a hydrophobic entity to the polymer terminus has been demonstrated for 8 classes of organic fluorophores. The resulting "pod-fluorophore" architecture is unimeric (∼15 nm in diameter) in aqueous solution with spectral features and fluorescence brightness resembling those of the benchmark fluorophore in organic solution. This strategy separates the functional design of the packaged molecular entity ("cargo") from the often vexing challenge of water solubilization and in so doing creates a unitary (one-pod-one-cargo) platform architecture for potential applications in cytometry, biomedical imaging, environmental sensing, and supramolecular chemistry.