Orthogonality in organic, polymer, and supramolecular chemistry: from Merrifield to click chemistry

Structural Landscape of α-Acetamidocinnamic Acid Cocrystals with Bipyridine-Based Coformers: Influence of Crystal Packing on Their Thermal and Photophysical Properties

Controlling the supramolecular synthon outcome in systems with different functionalities has been a key factor for the design of supramolecular materials, which also affected their physicochemical properties. In this contribution, we have analyzed the structural landscape of α-acetamidocinnamic acid (HACA) aiming to find its synthon outcome from the competitivity between its acidic and amidic groups. We prepared four multicomponent forms including one dihydrate (HACA·2H2O) and three cocrystals bearing different bipyridine coformers with formulas (HACA)2(1,2-bpe) (1), (HACA)2(4,4'-azpy) (2), and (HACA)2(4,4'-bipy)3 (3) (1,2-bpe = 1,2-bis(4-pyridyl)ethylene; 4,4'-azpy = 4,4'-azopyridine; 4,4'-bipy = 4,4'-bipyridine). First, we applied a virtual screening approach to assess the feasibility of cocrystal formation. Then, we synthesized the cocrystals, via liquid-assisted grinding (LAG) (1 and 2) or solvothermal (3) techniques, and single crystals of HACA, and their four multicomponent forms were obtained showing different synthons and crystal packings. Besides, a Cambridge Structural Database (CSD) search of the cocrystals presenting bipyridine-type coformers and molecules with acid and amide functionalities was performed, and the observed synthon occurrences as well as the possibility of synthon modification by tuning the H-donor/H-acceptor propensity of the acidic and amidic groups were shown. Finally, we measured their thermal and photophysical properties, which were correlated with their structural features.

New Insights on the Chemical Origin of Life: The Role of Aqueous Polymerization of N-carboxyanhydrides (NCA)

At the origin, the emergence of proteins was based on crucial prebiotic stages in which simple amino acids-based building blocks spontaneously evolved from the prebiotic soup into random proto-polymers called protoproteins. Despite advances in modern peptide synthesis, these prebiotic chemical routes to protoproteins remain puzzling. We discuss in this perspective how polymer science and systems chemistry are reaching a point of convergence in which simple monomers called N-carboxyanhydrides would be able to form such protoproteins via the emergence of a protometabolic cycle involving aqueous polymerization and featuring macromolecular Darwinism behavior.

Dynamic supramolecular hydrogels mediated by chemical reactions

Supramolecular self-assembly in a biological system is usually dominated by sophisticated metabolic processes (chemical reactions) such as catalysis of enzymes and consumption of high energy chemicals, leading to groups of biomolecules with unique dynamics and functions in an aqueous environment. In recent years, increasing efforts have been made to couple chemical reactions to molecular self-assembly, with the aim of creating supramolecular materials with lifelike properties and functions. In this feature article, after summarising the work of chemical reaction mediated supramolecular hydrogels, we first focus on a typical example where dynamic self-assembly of molecular hydrogels is activated by in situ formation of a hydrazone bond in water. We discuss how the formation of the hydrazone-based supramolecular hydrogels can be controlled in time and space. After that, we describe transient assembly of supramolecular hydrogels powered by out-of-equilibrium chemical reaction networks regulated by chemical fuels, which show unique properties such as finite lifetime, dynamic structures, and regenerative capabilities. Finally, we provide a perspective on the future investigations that need to be done urgently, which range from fundamental research to real-life applications of dynamic supramolecular hydrogels.

Dual reactivity based dynamic covalent chemistry: mechanisms and applications

Dynamic covalent chemistry (DCC) focuses on the reversible formation, breakage, and exchange of covalent bonds and assemblies, setting a bridge between irreversible organic synthesis and supramolecular chemistry and finding wide utility. In order to enhance structural and functional diversity and complexity, different types of dynamic covalent reactions (DCRs) are placed in one vessel, encompassing orthogonal DCC without crosstalk and communicating DCC with a shared reactive functional group. As a means of adding tautomers, widespread in chemistry, to interconnected DCRs and combining the features of orthogonal and communicating DCRs, a concept of dual reactivity based DCC and underlying structural and mechanistic insights are summarized. The manipulation of the distinct reactivity of structurally diverse ring-chain tautomers allows selective activation and switching of reaction pathways and corresponding DCRs (C-N, C-O, and C-S) and assemblies. The coupling with photoswitches further enables light-mediated formation and scission of multiple types of reversible covalent bonds. To showcase the capability of dual reactivity based DCC, the versatile applications in dynamic polymers and luminescent materials are presented, paving the way for future functionalization studies.

Aqueous Three-Component Self-Assembly of a Pseudo[1]rotaxane Using Hydrazone Bonds

We present herein the synthesis of a new polycationic pseudo[1]rotaxane, self-assembled in excellent yield through hydrazone bonds in aqueous media of three different aldehyde and hydrazine building blocks. A thermodynamically controlled process has been studied sequentially by analyzing the [1 + 1] reaction of a bisaldehyde and a trishydrazine leading to the macrocyclic part of the system, the ability of this species to act as a molecular receptor, the conversion of a hydrazine-pending cyclophane into the pseudo[1]rotaxane and, lastly, the one-pot [1 + 1 + 1] condensation process. The latter was found to smoothly produce the target molecule through an integrative social self-sorting process, a species that was found to behave in water as a discrete self-inclusion complex below 2.5 mM concentration and to form supramolecular aggregates in the 2.5-70 mM range. Furthermore, we demonstrate how the abnormal kinetic stability of the hydrazone bonds on the macrocycle annulus can be advantageously used for the conversion of the obtained pseudo[1]rotaxane into other exo-functionalized macrocyclic species.

Naphthyl-Poly(S-((2-carboxyethyl)thio)-l-cysteine) Peptide Amphiphiles with Different Degrees of Polymerization: Synthesis, Self-Assembly, pH/Reduction-Triggered Drug Release, and Cytotoxicity

Four peptide amphiphiles (PA1-4) with different degrees of polymerization (DP = 40, 15, 10, and 6) were synthesized by Fuchs-Farthing and ring-opening polymerization followed by post-polymerization modification, as fully characterized by ¹H NMR, FT-IR, gel permeation chromatography, and circular dichroism (CD) spectroscopy. It was found that PAs could self-assemble to form regular spherical micelles in low-concentration (about 1 mg/mL) aqueous solution, which had different contents of secondary structures and mainly adopted random coil conformations. The water solubility of PAs increases with the increase of DP, the polypeptide chain stretches randomly in water, the β-sheets decrease, and the random coil conformations dominate. When the pH of PA solution decreases or increases, intramolecular hydrogen bonds break, and molecular chains stretch, leading to a decrease of α-helix, turn conformations, and an increase of β-sheets. Meanwhile, the particle size of micelles increases. At around 0.4 mg/mL, the hemolysis ability of PA2 is negligible at pH 7.4 and 6.5 and about 33% at pH 5.5. Cisplatin (CDDP) was linked to micelles by coordination bonds to explore their potential as drug carriers, exhibiting controlled pH and reduction in dual drug release effects. MTT assay showed that the HeLa cell viability was 78% when cultured in the 13.5 μg/mL PA2 blank micelles for 2 days, while the cell viability was 60% in the CDDP-loaded micelles. Furthermore, a high concentration of PA2 (about 100 mg/mL) could self-assemble into a fibrous hydrogel at pH 5.5, which self-healed 2 h after incision and self-degraded 71% within 14 days. The CDDP-loaded fiber hydrogel exhibited a sustained release effect similar to the CDDP-loaded micelles. The cytotoxicity of CDDP-loaded fibers at 48 h was detected to be the same as that of the same amount of CDDP, and the cell viability was 7%. Therefore, we provide a new strategy for the synthesis of amphiphilic peptides with potential applications in nano-drug carriers and cancer therapy.

Shape-Dependent Complementary Ditopic Terpyridine Pair with Two Levels of Self-Recognition for Coordination-Driven Self-Assembly

Molecular recognition in biological systems plays a vital role in the precise construction of biomacromolecules and the corresponding biological activities. Such recognition mainly relies on the highly specific binding of complementary molecular pairs with complementary sizes, shapes, and intermolecular forces. It still remains challenging to develop artificial complementary motif pairs for coordination-driven self-assembly. Herein, a series of shape-dependent complementary motif pairs, based on ditopic 2,2':6',2″-terpyridine (TPY) backbone, are designed and synthesized. The fidelity degrees of self-assemblies from these motifs are carefully evaluated by multi-dimensional mass spectrometry, nuclear magnetic resonance spectroscopy, and molecular modeling. In addition, two levels of self-recognition in both homoleptic and heteroleptic assembly are discovered in the assembled system. Through finely tuning the shape and size of the ligands, a complementary pair is developed with error-free narcissistically self-sorting at two levels of self-recognition, and the intrinsic principle is carefully investigated.

Cucurbit[10]uril-Based Orthogonal Supramolecular Polymers with Host-Guest and Coordination Interactions and Its Applications in Anion Classification

A novel orthogonal supramolecular polymer (Q[10]-TPDPB-Lu³⁺) in a host-guest ratio of 2:1 was successfully constructed utilizing the specificity and excellent cavity matching of Q[10] with the tripyridine derivatives (TPDPB). Significantly, non-covalent interactions between Q[10]'s hydrophobic cavities and Lu³⁺ were used to induce charge transfer of TPDPB to TPDPB and TPDPB to Lu³⁺, resulting in the construction of structurally interesting orthogonal assemblies with excellent fluorescence properties. Finally, the Q[10]-TPDPB-Lu³⁺ assemblies were shown to have good recognition and classification of strong and weak acid anions as well as iodide anions, and the classification was accompanied by a clear fluorescence emission change allowing visual observation.

A Review of Multi-Material 3D Printing of Functional Materials via Vat Photopolymerization

Additive manufacturing or 3D printing of materials is a prominent process technology which involves the fabrication of materials layer-by-layer or point-by-point in a subsequent manner. With recent advancements in additive manufacturing, the technology has excited a great potential for extension of simple designs to complex multi-material geometries. Vat photopolymerization is a subdivision of additive manufacturing which possesses many attractive features, including excellent printing resolution, high dimensional accuracy, low-cost manufacturing, and the ability to spatially control the material properties. However, the technology is currently limited by design strategies, material chemistries, and equipment limitations. This review aims to provide readers with a comprehensive comparison of different additive manufacturing technologies along with detailed knowledge on advances in multi-material vat photopolymerization technologies. Furthermore, we describe popular material chemistries both from the past and more recently, along with future prospects to address the material-related limitations of vat photopolymerization. Examples of the impressive multi-material capabilities inspired by nature which are applicable today in multiple areas of life are briefly presented in the applications section. Finally, we describe our point of view on the future prospects of 3D printed multi-material structures as well as on the way forward towards promising further advancements in vat photopolymerization.

Pre-arranged building block approach for the orthogonal synthesis of an unfolded tetrameric organic-inorganic phosphazane macrocycle

Inorganic macrocycles remain challenging synthetic targets due to the limited number of strategies reported for their syntheses. Among these species, large fully inorganic cyclodiphosphazane macrocycles have been experimentally and theoretically highlighted as promising candidates for supramolecular chemistry. In contrast, their hybrid organic-inorganic counterparts are lagging behind due to the lack of synthetic routes capable of controlling the size and topological arrangement (i.e., folded vs unfolded) of the target macrocycle, rendering the synthesis of differently sized macrocycles a tedious screening process. Herein, we report-as a proof-of-concept-the combination of pre-arranged building blocks and a two-step synthetic route to rationally enable access a large unfolded tetrameric macrocycle, which is not accessible via conventional synthetic strategies. The obtained macrocycle hybrid cyclodiphosphazane macrocycle, cis-[μ-P(μ-N^tBu)]₂(μ-p-OC₆H₄C(O)O)]₄[μ-P(μ-N^tBu)]₂ (4), displays an unfolded open-face cavity area of 110.1 Ų. Preliminary theoretical host-guest studies with the dication [MeNC₅H₄]₂²⁺ suggest compound 4 as a viable candidate for the synthesis of hybrid proto-rotaxanes species based on phosphazane building blocks.

Orthogonal chemistry in the design of rare-earth metal oxyhydrides

Inorganic systems containing two or more kinds of anions, such as rare-earth metal oxyhydrides, have a number of interesting properties that can be used in the design and development of new functional materials with desired characteristics. Chemical synthesis of these materials can be accomplished by oxidation of metal hydrides. However, the oxidation process of a metal hydride is directly accompanied by the release of hydrogen; both processes are a combination of two sequential reactions. This is usually not favorable for the formation and crystallization of the ternary oxyhydride composition. One possible way to overcome this problem is to introduce an appropriate amount of oxygen atoms into certain interstitial positions adjacent to the metal sites of the hydride lattice. Guided by the ideas of orthogonality, we have proposed a theoretical model capable of providing a thorough understanding of the chemical processes occurring in a multicomponent system at the molecular level. This model opens the way for predicting a wide range of new, stable multi-anion compounds of different compositions. It can also control functionality by adding noncovalent interactions between different kinds of anions, which can lead to the formation of chiral structures or a significant increase in ferro- and piezoelectric properties.

Enzymatic and Chemical Approaches for Post-Polymerization Modifications of Diene Rubbers: Current state and Perspectives

Diene rubbers are polymeric materials which present elastic properties and have double bonds in the macromolecular backbone after the polymerization process. Post-polymerization modifications of rubbers can be conducted by enzymatic or chemical methods. Enzymes are environmentally friendly catalysts and with the increasing demand for rubber waste management, biodegradation and biomodifications have become hot topics of research. Some rubbers are renewable materials and are a source of organic molecules, and biodegradation can be conducted to obtain either oligomers or monomers. On the other hand, chemical modifications of rubbers by click-chemistry are important strategies for the creation and combination of new materials. In a way to expand the scope of uses to other non-traditional applications, several and effective modifications can be conducted with diene rubbers. Two groups of efficient tools, enzymatic, and chemical modifications in diene rubbers, are summarized in this review. By analyzing stereochemical and reactivity aspects, the authors also point to some applications perspectives for biodegradation products and to rational modifications of diene rubbers by combining both methodologies.

Synergistic effect of serine protease inhibitors and a bothropic antivenom in reducing local hemorrhage and coagulopathy caused by Bothrops jararaca venom

Snakebite accidents are a public health problem that affects the whole world, causing thousands of deaths and amputations each year. In Brazil, snakebite envenomations are caused mostly by snakes from the Bothrops genus. The local symptoms are characterized by pain, swelling, ecchymosis, and hemorrhages. Systemic disturbances can lead to necrosis and amputations. The present treatment consists of intravenous administration of bothropic antivenom, which is capable of reversing most of the systemic symptoms, while presenting limitations to treat the local effects, such as hemorrhage and to neutralize the snake venom serine protease (SVSP). In this context, we aimed to evaluate the activity of selective serine protease inhibitors (pepC and pepB) in combination with the bothropic antivenom in vivo. Further, we assessed their possible synergistic effect in the treatment of coagulopathy and hemorrhage induced by Bothrops jararaca venom. For this, we evaluated the in vivo activity in mouse models of local hemorrhage and a series of in vitro hemostasis assays. Our results showed that pepC and pepB, when combinated with the antivenom, increase its protective activity in vivo and decrease the hemostatic disturbances in vitro with high selectivity, possibly by inhibiting botropic proteases. These data suggest that the addition of serine protease inhibitor to the antivenom can improve its overall potential.

Developments in Treatment Methodologies Using Dendrimers for Infectious Diseases

Dendrimers comprise a specific group of macromolecules, which combine structural properties of both single molecules and long expanded polymers. The three-dimensional form of dendrimers and the extensive possibilities for use of additional substrates for their construction creates a multivalent potential and a wide possibility for medical, diagnostic and environmental purposes. Depending on their composition and structure, dendrimers have been of interest in many fields of science, ranging from chemistry, biotechnology to biochemical applications. These compounds have found wide application from the production of catalysts for their use as antibacterial, antifungal and antiviral agents. Of particular interest are peptide dendrimers as a medium for transport of therapeutic substances: synthetic vaccines against parasites, bacteria and viruses, contrast agents used in MRI, antibodies and genetic material. This review focuses on the description of the current classes of dendrimers, the methodology for their synthesis and briefly drawbacks of their properties and their use as potential therapies against infectious diseases.

A calix[4]pyrrole-based linear supramolecular polymer constructed by orthogonal self-assembly

A calix[4]pyrrole having a ureidopyrimidinone unit was successfully synthesized from its alcohol-functionalized congener and further used for the first time to obtain a thermo- and chemical-responsive linear supramolecular polymer via orthogonal self-assembly comprising a combination of quadruple hydrogen bonding and anion recognition.

Multidentate, V-Shaped Pyridine Building Blocks as Tectons for Crystal Engineering

The formation of supramolecular structural units through self-assembly is a powerful method to design new architectures and materials endowed with specific properties. With the aim of adding a group of versatile tectons to the toolkit of crystal engineers, we have devised and synthesised four new V-shaped building blocks characterised by an aryl acetylene scaffold comprising three substituted pyridine rings connected by two triple bonds. The judicious choice of different substituents on the pyridine rings provides these tectons with distinctive steric, electrostatic and self-assembly properties, which influence their crystal structures and their ability to form co-crystals. Co-crystals of the tectons with tetraiododifluorobenzene were obtained both via traditional and mechanochemical crystallisation strategies, proving their potential use in crystal engineering. The energetic contributions of the supramolecular interactions at play in the crystal lattice have also been evaluated to better understand their nature and strength and to rationalise their role in designing molecular crystals.

Injury-mediated stiffening persistently activates muscle stem cells through YAP and TAZ mechanotransduction

The skeletal muscle microenvironment transiently remodels and stiffens after exercise and injury, as muscle ages, and in myopathic muscle; however, how these changes in stiffness affect resident muscle stem cells (MuSCs) remains understudied. Following muscle injury, muscle stiffness remained elevated after morphological regeneration was complete, accompanied by activated and proliferative MuSCs. To isolate the role of stiffness on MuSC behavior and determine the underlying mechanotransduction pathways, we cultured MuSCs on strain-promoted azide-alkyne cycloaddition hydrogels capable of in situ stiffening by secondary photocrosslinking of excess cyclooctynes. Using pre- to post-injury stiffness hydrogels, we found that elevated stiffness enhances migration and MuSC proliferation by localizing yes-associated protein 1 (YAP) and WW domain-containing transcription regulator 1 (WWTR1; TAZ) to the nucleus. Ablating YAP and TAZ in vivo promotes MuSC quiescence in postinjury muscle and prevents myofiber hypertrophy, demonstrating that persistent exposure to elevated stiffness activates mechanotransduction signaling maintaining activated and proliferating MuSCs.

Design, synthesis, and evaluation of Bothrops venom serine protease peptidic inhibitors

Background:

In Central and South America, snakebite envenomation is mainly caused by Bothrops spp. snakes, whose venoms feature significant biochemical richness, including serine proteases. The available bothropic antivenoms are efficient in avoiding fatalities, but do not completely neutralize venom serine proteases, which are co-responsible for some disorders observed during envenomation.

Methods:

In order to search for tools to improve the antivenom’s, 6-mer peptides were designed based on a specific substrate for Bothrops jararaca venom serine proteases, and then synthesized, with the intention to selectively inhibit these enzymes.

Results:

Using batroxobin as a snake venom serine protease model, two structurally similar inhibitor peptides were identified. When tested on B. jararaca venom, one of the new inhibitors displayed a good potential to inhibit the activity of the venom serine proteases. These inhibitors do not affect human serine proteases as human factor Xa and thrombin, due to their selectivity.

Conclusion:

Our study identified two small peptides able to inhibit bothropic serine proteases, but not human ones, can be used as tools to enhance knowledge of the venom composition and function. Moreover, one promising peptide (pepC) was identified that can be explored in the search for improving Bothrops spp. envenomation treatment.

Click Chemistry Enabling Covalent and Non-Covalent Modifications of Graphene with (Poly)saccharides

Graphene is a material with outstanding properties and numerous potential applications in a wide range of research and technology areas, spanning from electronics, energy materials, sensors, and actuators to life-science and many more. However, the insolubility and poor dispersibility of graphene are two major problems hampering its use in certain applications. Tethering mono-, di-, or even poly-saccharides on graphene through click-chemistry is gaining more and more attention as a key modification approach leading to new graphene-based materials (GBM) with improved hydrophilicity and substantial dispersibility in polar solvents, e.g., water. The attachment of (poly)saccharides on graphene further renders the final GBMs biocompatible and could open new routes to novel biomedical and environmental applications. In this review, recent modifications of graphene and other carbon rich materials (CRMs) through click chemistry are reviewed.

Perfluorocarbons in Chemical Biology

Perfluorocarbons, saturated carbon chains in which all the hydrogen atoms are replaced with fluorine, form a separate phase from both organic and aqueous solutions. Though perfluorinated compounds are not found in living systems, they can be used to modify biomolecules to confer orthogonal behavior within natural systems, such as improved stability, engineered assembly, and cell-permeability. Perfluorinated groups also provide handles for purification, mass spectrometry, and 19 F NMR studies in complex environments. Herein, we describe how the unique properties of perfluorocarbons have been employed to understand and manipulate biological systems.

Light-Activated Olefin Metathesis: Catalyst Development, Synthesis, and Applications

The most important means for tuning and improving a catalyst's properties is the delicate exchange of the ligand shell around the central metal atom. Perhaps for no other organometallic-catalyzed reaction is this statement more valid than for ruthenium-based olefin metathesis. Indeed, even the simple exchange of an oxygen atom for a sulfur atom in a chelated ruthenium benzylidene about a decade ago resulted in the development of extremely stable, photoactive catalysts. This Account presents our perspective on the development of dormant olefin metathesis catalysts that can be activated by external stimuli and, more specifically, the use of light as an attractive inducing agent.The insight gained from a deeper understanding of the properties of cis-dichlororuthenium benzylidenes opened the doorway for the systematic development of new and efficient light-activated olefin metathesis catalysts and catalytic chromatic-orthogonal synthetic schemes. Following this, ways to disrupt the ligand-to-metal bond to accelerate the isomerization process that produced the active precatalyst were actively pursued. Thus, we summarize herein the original thermal activation experiments and how they brought about the discoveries of photoactivation in the sulfur-chelated benzylidene family of catalysts. The specific wavelengths of light that were used to dissociate the sulfur-ruthenium bond allowed us to develop noncommutative catalytic chromatic-orthogonal processes and to combine other photochemical reactions with photoinduced olefin metathesis, including using external light-absorbing molecules as "sunscreens" to achieve novel selectivities. Alteration of the ligand sphere, including modifications of the N-heterocyclic carbene (NHC) ligand and the introduction of cyclic alkyl amino carbene (CAAC) ligands, produced more efficient light-induced activity and special chemical selectivity. The use of electron-rich sulfoxides and, more prominently, phosphites as the agents that induce latency widened the spectrum of light-induced olefin metathesis reactions even further by expanding the colors of light that may now be used to activate the catalysts, which can be used in applications such as stereolithography and 3D printing of tough metathesis-derived polymers.

Mixed Polymer Brushes for "Smart" Surfaces

Mixed polymer brushes (MPBs) are composed of two or more disparate polymers covalently tethered to a substrate. The resulting phase segregated morphologies have been extensively studied as responsive "smart" materials, as they can be reversible tuned and switched by external stimuli. Both computational and experimental work has attempted to establish an understanding of the resulting nanostructures that vary as a function of many factors. This contribution highlights state-of-the-art MPBs studies, covering synthetic approaches, phase behavior, responsiveness to external stimuli as well as novel applications of MPBs. Current limitations are recognized and possible directions for future studies are identified.

Combining Coordination and Hydrogen Bonds to Develop Discrete Supramolecular Metalla-Assemblies

In Nature, metal ions play critical roles at different levels, and they are often found in proteins. Therefore, metal ions are naturally incorporated in hydrogen-bonded systems. In addition, the combination of metal coordination and hydrogen bonds have been used extensively to develop supramolecular materials. However, despite this win-win combination between coordination and hydrogen bonds in many supramolecular systems, the same combination remains scarce in the field of coordination-driven self-assemblies. Indeed, as illustrated in this mini-review, only a few discrete supramolecular metalla-assemblies combining coordination and hydrogen bonds can be found in the literature, but that figure might change rapidly.

N-Heterocyclic Carbene Copper(I) Rotaxanes Mediate Sequential Click Ligations with All Reagents Premixed

We have prepared NHC-Cu^I complexes with a rotaxane structure and used them as sterically sensitive catalysts for one-pot sequential copper-catalyzed azide/alkyne cycloadditions in solutions containing all of the coupling partners premixed in unprotected form. Most notably, a photolabile and sterically encumbered complex first catalyzed the coupling of a less bulky azide/alkyne pair; after removing the protective macrocyclic component from the rotaxane structure, through irradiation with light, the exposed dumbbell-shaped NHC-Cu^I complex catalyzed the second click reaction of a bulkier azide/alkyne pair. Using this approach, we obtained predominantly, from a single sealed pot, a bis-triazole product (84 %) from a mixture of two sterically distinct azides and a diyne.

Well-Defined Conjugated Macromolecules Based on Oligo(Arylene Ethynylene)s in Sensing

Macromolecules with well-defined structures in terms of molar mass and monomer sequence became interesting building blocks for modern materials. The precision of the macromolecular structure makes fine-tuning of the properties of resulting materials possible. Conjugated macromolecules exhibit excellent optoelectronic properties that make them exceptional candidates for sensor construction. The importance of chain length and monomer sequence is particularly important in conjugated systems. The oligomer length, monomer sequence, and structural modification often influence the energy bang gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the molecules that reflect in their properties. Moreover, the supramolecular aggregation that is often observed in oligo-conjugated systems is usually strongly affected by even minor structural changes that are used for sensor designs. This review discusses the examples of well-defined conjugated macromolecules based on oligo(arylene ethynylene) skeleton used for sensor applications. Here, exclusively examples of uniform macromolecules are summarized. The sensing mechanisms and importance of uniformity of structure are deliberated.

Sunscreen-Assisted Selective Photochemical Transformations

In this review, we describe a simple and general procedure to accomplish selective photochemical reaction sequences for two chromophores that are responsive to similar light frequencies. The essence of the method is based on the exploitation of differences in the molar absorptivity at certain wavelengths of the photosensitive groups, which is enhanced by utilizing light-absorbing auxiliary filter molecules, or “sunscreens”. Thus, the filter molecule hinders the reaction pathway of the least absorbing molecule or group, allowing for the selective reaction of the other. The method was applied to various photochemical reactions, from photolabile protecting group removal to catalytic photoinduced olefin metathesis in different wavelengths and using different sunscreen molecules. Additionally, the sunscreens were shown to be effective also when applied externally to the reaction mixture, avoiding any potential chemical interactions between sunscreen and substrates and circumventing the need to remove the light-filtering molecules from the reaction mixture, adding to the simplicity and generality of the method.

Photo-induced thiol-ene reactions for late-stage functionalization of unsaturated polyether macrocycles: regio and diastereoselective access to macrocyclic dithiol derivatives

Double hydrothiolation of bis enol ether macrocycles was achieved under photo-mediated conditions. The thiol-ene reactions afford a fully regioselective anti-Markovnikov post-functionalization. Thanks to the use of ethanedithiol as reagent, moderate to excellent diastereoselectivity was accomplished leading to macrocycles containing four defined stereocenters in only three steps from 1,4-dioxane, tetrahydrofuran (THF) or tetrahydropyran (THP).

Assembly of miscible supramolecular network blends using DDA·AAD hydrogen-bonding interactions of pendent side-chains

Miscible blends of poly(methyl methacrylate) and polystyrene polymers are assembled through triple hydrogen bonding between complementary ureidoimidazole and amidoisocytosine heterodimers.

Cellular Uptake Evaluation of Amphiphilic Polymer Assemblies: Importance of Interplay between Pharmacological and Genetic Approaches

Understanding the cellular uptake mechanism of materials is of fundamental importance that would be beneficial for materials design with enhanced biological functions. Herein, we report the interplay of pharmacological and genetic approaches to minimize the possible misinterpretation on cellular uptake mechanism. A library of amphiphilic polymers was used as a model system to evaluate the reliability of such methodological interplay. To probe the cellular uptake of amphiphilic polymers, we utilized an orthogonal end-group labeling strategy to conjugate one fluorescent molecule on each polymer chain. The results from the methodological interplay with these labeled polymers revealed the off-target effects of dynasore, a well-known dynamin inhibitor. Instead of dynamin, actin was found to be an essential cellular component during the cellular uptake of these amphiphilic polymers. Our study demonstrates the importance of interplaying pharmacological and genetic approaches when evaluating the endocytic mechanism of functional materials, providing insights on understanding the cellular uptake of future therapeutic materials.