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200 years of research with carbon-rich molecules have shaped the development of modern chemistry. Research pertaining to the chemistry of boron-rich species has historically trailed behind its more distinguished neighbor (carbon) in the periodic table. Notably, a potentially rich and, in many cases, unmatched field of coordination chemistry using boron-rich clusters remains fundamentally underdeveloped. Our work has been devoted to examining several basic concepts related to the functionalization of icosahedral boron-rich clusters and their use as ligands, aimed at designing fundamentally new hybrid molecular motifs and materials. Particularly interesting are icosahedral carboranes, which can be regarded as 3D analogs of benzene. These species comprise a class of boron-rich clusters that were discovered in the 1950s during the “space race” while researchers were developing energetic materials for rocket fuels. Ultimately, the unique chemical and physical properties of carborane species, such as rigidity, indefinite stability to air and moisture, and 3D aromaticity, may allow one to access a set of properties not normally available in carbon-based chemistry. While technically these species are considered as inorganic clusters, the chemical properties they possess make these boron-rich species suitable for replacing and/or altering structural and functional features of the organic and organometallic molecules—a phenomenon best described as “organomimetic”. Aside from purely fundamental features associated with the organomimetic chemistry of icosahedral carboranes, their use can also provide new avenues in the development of systems relevant to solving current problems associated with energy production, storage, and conversion.

The majority of biomolecules are intrinsically atomically precise, an important characteristic that enables rational engineering of their recognition and binding properties. However, imparting a similar precision to hybrid nanoparticles has been challenging because of the inherent limitations of existing chemical methods and building blocks. Here we report a new approach to form atomically precise and highly tunable hybrid nanomolecules with well-defined three-dimensionality. Perfunctionalization of atomically precise clusters with pentafluoroaryl-terminated linkers produces size-tunable rigid cluster nanomolecules. These species are amenable to facile modification with a variety of thiol-containing molecules and macromolecules. Assembly proceeds at room temperature within hours under mild conditions, and the resulting nanomolecules exhibit high stabilities because of their full covalency. We further demonstrate how these nanomolecules grafted with saccharides can exhibit dramatically improved binding affinity towards a protein. Ultimately, the developed strategy allows the rapid generation of precise molecular assemblies to investigate multivalent interactions. The operational simplicity of modifying the surfaces of thiol-capped gold nanoparticles has been a hallmark of their success in materials chemistry, despite having limited control over the surface composition. Now, S N Ar chemistry on activated perfluoroaromatics has been shown to mimic this simplicity and allow for the synthesis of atomically precise nanomolecules.

Although the majority of ligands in modern chemistry take advantage of carbon-based substituent effects to tune the sterics and electronics of coordinating moieties, we describe here how icosahedral carboranes—boron-rich clusters—can influence metal–ligand interactions. Using a series of phosphine–thioether chelating ligands featuring meta- or ortho-carboranes grafted on the sulfur atom, we were able to tune the lability of the platinum–sulfur interaction of platinum( II )–thioether complexes. Experimental observations, supported by computational work, show that icosahedral carboranes can act either as strong electron-withdrawing ligands or electron-donating moieties (similar to aryl- or alkyl-based groups, respectively), depending on which atom of the carborane cage is attached to the thioether moiety. These and similar results with carborane-selenol derivatives suggest that, in contrast to carbon-based ligands, icosahedral carboranes exhibit a significant dichotomy in their coordination chemistry, and can be used as a versatile class of electronically tunable building blocks for various ligand platforms. Rather than tuning metal–ligand interactions using carbon-based substituents, the effect of icosahedral carborane moieties — boron-rich clusters — on the coordination chemistry of phosphine–thioether ligands has been investigated. Depending on the positional attachment of the sulfur atom, the carboranes acted as either strong electron-withdrawing or strong electron-donating substituents.

Introducing a tri-coordinate boron-based functional group (e.g., boronic ester) into an unactivated C–H bond in the absence of directing groups is an ongoing challenge in synthetic chemistry. Despite previous developments in transition metal-catalyzed and -free approaches, C–H borylation of sterically hindered arenes remains a largely unsolved problem to date. Here, we report a synthetic strategy of a two-step, precious metal-free electrophilic C–H borylation of sterically hindered alkyl- and haloarenes to generate aryl boronic esters. The first step relies on electrophilic aromatic substitution (EAS) induced by cage-opening of Cs 2 [ closo -B 10 H 10 ], forming a 6-Ar- nido -B 10 H 13 product containing a B–C bond, followed by a cage deconstruction of arylated decaboranes promoted by diols. The combination of these two steps allows for the preparation of aryl boronic esters that are hardly accessible by current direct C–H borylation approaches. This reaction does not require any precious metals, highly-engineered ligands, pre-functionalized boron reagents, or inert conditions. In addition, the unique properties of a non-classical boron cluster electrophile intermediate, B 10 H 13 + , afford a regioselectivity with unique steric and electronic control without the undesirable side reactions. Electrophilic borylation of sterically hindered arenes is a challenging transformation. Here, authors report a metal-free electrophilic C–H borylation of hindered arenes using a boron cluster reagent producing valuable aryl boronic esters.

A boron cluster is used to template a hybrid molecular scaffold capable of killing multiple pathogenic and antibiotic-resistant bacterial strains.

Palladium( ii ) complexes can be used in efficient and highly selective cysteine conjugation reactions that are rapid and robust, and the resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. A new route to S -aryl conjugates These authors demonstrate that palladium( II ) complexes can be used in efficient and highly selective cysteine conjugation reactions that are rapid and robust, and the resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the new bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody–drug conjugates. Previously the use of transition-metal based reactions to modify complex biomolecules has proved problematic due mainly to the need for stringent reaction conditions and the presence of multiple reactive functional groups in peptides. Reactions based on transition metals have found wide use in organic synthesis, in particular for the functionalization of small molecules 1 , 2 . However, there are very few reports of using transition-metal-based reactions to modify complex biomolecules 3 , 4 , which is due to the need for stringent reaction conditions (for example, aqueous media, low temperature and mild pH) and the existence of multiple reactive functional groups found in biomolecules. Here we report that palladium( ii ) complexes can be used for efficient and highly selective cysteine conjugation (bioconjugation) reactions that are rapid and robust under a range of bio-compatible reaction conditions. The straightforward synthesis of the palladium reagents from diverse and easily accessible aryl halide and trifluoromethanesulfonate precursors makes the method highly practical, providing access to a large structural space for protein modification. The resulting aryl bioconjugates are stable towards acids, bases, oxidants and external thiol nucleophiles. The broad utility of the bioconjugation platform was further corroborated by the synthesis of new classes of stapled peptides and antibody–drug conjugates. These palladium complexes show potential as benchtop reagents for diverse bioconjugation applications.

Metal oxides are ubiquitous in our daily lives because they are robust and possess versatile electrochemical properties. Despite their popularity, these materials present limitations with respect to effective large-scale implementation. Recently, there has been growing interest in creating hybrid metal oxides to tailor the morphology and properties of these materials. From this perspective, we highlight several recent developments in cross-linked hybrid metal oxides, focusing on chemical cross-linking techniques to enrich their properties. We discuss future directions of this cross-linking approach that could enable further manipulation of these materials.Chemical cross-linking represents a unique approach for creating hybrid materials with enriched properties. This method facilitates the formation of interconnected networks within the material, which can modulate its porosity, conductivity and photophysical properties. Porous morphologies are beneficial for electrochemical applications as they enable the smooth diffusion and penetration of ions, effective ion transport at material interfaces, and also offer a synergy of the properties of the constituent materials and cross-linker. This perspective article highlights the recent advances in the area of covalently cross-linked hybrid metal oxides.

There is significant interest in the development of methods to create hybrid materials that transform capabilities, in particular for Earth-abundant metal oxides, such as TiO2, to give improved or new properties relevant to a broad spectrum of applications. Here we introduce an approach we refer to as ‘molecular cross-linking’, whereby a hybrid molecular boron oxide material is formed from polyhedral boron-cluster precursors of the type [B12(OH)12]2–. This new approach is enabled by the inherent robustness of the boron-cluster molecular building block, which is compatible with the harsh thermal and oxidizing conditions that are necessary for the synthesis of many metal oxides. In this work, using a battery of experimental techniques and materials simulation, we show how this material can be interfaced successfully with TiO2 and other metal oxides to give boron-rich hybrid materials with intriguing photophysical and electrochemical properties.

The chloride gradient plays an important role in regulating cell volume, membrane potential, pH, secretion, and the reversal potential of inhibitory glycine and GABA A receptors. Measurement of intracellular chloride activity, a Cl i , using liquid membrane ion-selective microelectrodes (ISM), however, has been limited by the physiochemical properties of Cl − ionophores which have caused poor stability, drift, sluggish response times, and interference from other biologically relevant anions. Most importantly, intracellular HC O 3 − may be up to 4 times more abundant than Cl − (e.g. skeletal muscle) which places severe constraints on the required selectivity of a Cl − – sensing ISM. Previously, a sensitive and highly-selective Cl − sensor was developed in a polymeric membrane electrode using a trinuclear Hg(II) complex containing carborane-based ligands, [9]-mercuracarborand-3, or MC3 for short. Here, we have adapted the use of the MC3 anion carrier in a liquid membrane ion-selective microelectrode and show the MC3-ISM has a linear Nernstian response over a wide range of a Cl (0.1 mM to 100 mM), is highly selective for Cl − over other biological anions or inhibitors of Cl − transport, and has a 10% to 90% settling  time of 3  sec. Importantly, over the physiological range of a Cl (1 mM to 100 mM) the potentiometric response of the MC3-ISM is insensitive to HC O 3 − or changes in pH. Finally, we demonstrate the biological application of an MC3-ISM by measuring intracellul a r a Cl , and the response to an external Cl-free challenge, for an isolated skeletal muscle fiber.

In the version of this Article originally published, Liban M. A. Saleh was incorrectly listed as Liban A. M. Saleh due to a technical error. This has now been amended in all online versions of the Article.