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Bioconjugation techniques for biomolecule-polymer conjugation are numerous, however, slow kinetics and steric challenges generally necessitate excess reagents or long reactions times. Organometallic transformations are known to circumvent these issues; however, harsh reaction conditions, incompatibility in aqueous media and substrate promiscuity often limit their use in a biological context. This work reported herein, demonstrates a facile and benign organometallic Au(III) S-arylation approach that enables the synthesis of poly(ethylene glycol) monomethyl ether (mPEG)-protein conjugates with high efficiency. Isolable and bench-stable 2, 5, and 10 kDa mPEG-Au(III) reagents were synthesized via oxidative addition into terminal aryl iodide substituents installed on mPEG substrates with a (Me-DalPhos)Au(I)Cl precursor. Reaction of the isolable mPEG-Au(III) oxidative addition complexes with a cysteine thiol on a biomolecule resulted in facile and selective cysteine arylation chemistry forging covalent S-aryl linkages and affording the stable mPEG-biomolecule conjugates. Notably, low polymer reagent loadings were used to achieve near quantitative conversion at room temperature in one minute due to the rapid kinetics and high chemoselectivity of this Au-based bioconjugation approach. Therefore, this work represents an important addition to the protein-polymer conjugation chemical tool box.

Herein, we report the use of sterically invariant carborane-based chalcogenols, containing exopolyhedral B–Se or B–S bonds, as ligands for the formation of photoluminescent copper(I)-based metal–organic chalcogenolate assemblies (MOCHAs). We show that precise tuning of the carborane dipole by changing the carborane isomer from meta to ortho allows for control over the MOCHA morphology and regulation of the resulting photophysical properties. Furthermore, microcrystal electron diffraction (MicroED) has been demonstrated as a powerful tool for metal chalcogenide structure elucidation. Through the use of MicroED, one of the isolated materials is determined to consist of zero-dimensional Cu₄(Se–C₂B₁₀H₁₁)₄ clusters with an unprecedented Cu₄Se₄ geometry.

The (18)F-labeling of unprotected peptides and sugars with a Au(III)-[(18)F]fluoroaryl complex is reported. The chemoselective method generates (18)F-labeled S-aryl bioconjugates in an aqueous environment in 15 min with high radiochemical yields and displays excellent functional group tolerance. This approach utilizes an air and moisture stable, robust organometallic Au(III) complex and highlights the versatility of designer organometallic reagents as efficient agents for rapid radiolabeling.

The dynamic photoluminescence properties, and potential quenching mechanisms, of anti-B18H22, 4,4′-Br2-anti-B18H20, and 4,4′-I2-anti-B18H20 are investigated in solution and polymer films.

We report the synthesis and characterization of a 2D coordination polymer composed of a dianionic perhydroxylated boron cluster, [B12(OH)122−], coordinated to Zn(ii)—the first example of a transition metal-coordinated [B12(OH)12]2− compound.

Chalcogen-containing carboranes have been known for several decades and possess stable exopolyhedral B(9)-Se and B(9)-Te σ bonds despite the electron-donating ability of the B(9) vertex. While these molecules are known, little has been done to thoroughly evaluate their electrophilic and nucleophilic behavior. Herein, we report an assessment of the electrophilic reactivity of meta-carboranyl selenyl (II), tellurenyl (II), and tellurenyl (IV) chlorides and establish their reactivity pattern with Grignard reagents, alkenes, alkynes, enolates, and electron-rich arenes. These electrophilic reactions afford unique electron-rich B-Y-C (Y = Se, Te) bonding motifs not commonly found before. Furthermore, we show that meta-carboranyl selenolate, and even meta-carboranyl tellurolate, can be competent nucleophiles and participate in nucleophilic aromatic substitution reactions. Arene substitution chemistry is shown to be further extended to electron-rich species via the palladium mediated cross-coupling chemistry.

Synthetic bioconjugation at cysteine (Cys) residues in peptides and proteins has emerged as a powerful tool in chemistry. Soft nucleophilicity of the sulfur in Cys renders an exquisite chemoselectivity with which various functional groups can be placed onto this residue under benign conditions. While a variety of reactions have been successful at producing Cys-based bioconjugates, the majority of these feature sulfur-carbon bonds. We report Cys-borylation, wherein a benchtop stable Pt(II)-based organometallic reagent can be used to transfer a boron-rich cluster onto a sulfur moiety in unprotected peptides forging a boron-sulfur bond. Cys-borylation proceeds at room temperature and tolerates a variety of functional groups present in complex polypeptides. Further, the bioconjugation strategy can be applied to a model protein modification of Cys-containing DARPin (designed ankyrin repeat protein). The resultant bioconjugates show no additional toxicity compared to their Cys alkyl-based congeners. Finally, we demonstrate how the developed Cys-borylation can enhance the proteolytic stability of the resultant peptide bioconjugates while maintaining the binding affinity to a protein target.

This study details the design and implementation of an online materials chemistry general education (GE) course during the COVID-19 pandemic. While many pedagogical techniques involving active learning have been established in STEM major courses, their use within STEM general education courses for non-majors are not as well-established. The recently developed GE course at UCLA (termed Chemistry 3: Material World) utilized high-impact practices to introduce students to the scientific process and impart skills of critical thinking and scientific communication through its flexible activities and assignments. Emphasis was placed on collaborative learning, problem-solving, and interpreting scientific information from published reports. Additionally, content focused on social justice and community engagement was introduced throughout several topics (e.g., underrepresentation in science, war on drugs, nuclear proliferation, pollution, and global climate change) to showcase that chemistry is intricately related to bigger societal challenges. This article details our efforts in achieving the course learning outcomes and shares tangible results regarding the assessment of our teaching strategies from student feedback and reflections. We envision that this work will assist faculty in designing inclusive chemistry GE courses that focus on process versus content and adopting our teaching strategies in both in-person and online classrooms.

This work describes select narratives pertaining to undergraduate teaching and mentorship at UCLA Chemistry and Biochemistry by Alex Spokoyny and his junior colleagues. Specifically, we discuss how individual undergraduate researchers contributed and jump-started multiple research themes since the conception of our research laboratory. This work also describes several recent innovations in the inorganic and general chemistry courses taught by Spokoyny at UCLA with a focus of nurturing appreciation for research and creative process in sciences including the use of social media platforms.

A set of two dodecaborate [B(12)(OR)(12)](1−) radical cluster anions containing a dense layer of fluorinated end-groups provide nuclear spin hyperpolarization via the dissolution dynamic nuclear polarization (D-DNP) technique. We show that these clusters can enhance (19)F nuclear magnetic resonance (NMR) signals. Importantly, given the inherent radical delocalization in dodecaborate-based radicals, these species are compatible with reactive compounds such as Lewis acids, providing ~ 1000 – 2000 times of signal enhancement for B(C(6)F(5))(3) in liquid state NMR experiments at 9.4 T. This observation suggests that 3D aromatic radicals can provide advantages over the conventional radical species that are currently used for DNP, such as 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) by showing superior chemical compatibility. The ability to hyperpolarize reactive compounds using [B(12)(OR)(12)](1−) cluster radicals opens up new applications of reaction monitoring by D-DNP NMR spectroscopy, including the observation of catalytically active species in complex reaction mixtures.

Porous metal-organic framework (MOF) materials can be synthesized with precise spatial control of coordinatively unsaturated Mg2+ sites within the pore interior. Zick and co-workers show how these Mg2+ sites can dictate selective interactions between the MOF-based absorbent and molecules containing C-F bonds.

Host-guest interactions represent a growing research area with recent work demonstrating the ability to chemically manipulate both host molecules as well as guest molecules to vary the type and strength of bonding. Much less is known about the interactions of the guest molecules and hybrid materials containing similar chemical features to typical macrocyclic hosts. This work uses in vitro and in vivo kinetic analyses to investigate the interaction of closo-dodecahydrododecaborate derivatives with ferumoxytol, an iron oxide nanoparticle with a carboxylated dextran coating. We find that several boron cluster derivatives can become encapsulated into ferumoxytol, and the lack of pH dependence in these interactions suggests that ion pairing, hydrophobic/hydrophilic interaction, and hydrogen bonding are not the driving force for encapsulation in this system. Biodistribution experiments in BALB/c mice show that this system is nontoxic at the reported dosage and demonstrate that encapsulation of dodecaborate-based clusters in ferumoxytol can alter the biodistribution of the guest molecules.

Multivalent protein-protein interactions serve central roles in many essential biological processes, ranging from cell signaling and adhesion to pathogen recognition. Uncovering the rules that govern these intricate interactions is important not only to basic biology and chemistry, but also to the applied sciences where researchers are interested in developing molecules to promote or inhibit these interactions. Here we report the synthesis and application of atomically precise inorganic cluster nanomolecules consisting of an inorganic core and a covalently linked densely-packed layer of saccharides. These hybrid agents are stable under biologically relevant conditions and exhibit multivalent binding capabilities, which enable us to study the complex interactions between glycosylated structures and a dendritic cell lectin receptor. Importantly, we find that subtle changes in the molecular structure lead to significant differences in the nanomolecule’s protein-binding properties. Furthermore, we demonstrate an example of using these hybrid nanomolecules to effectively inhibit protein-protein interactions in a human cell line. Ultimately, this work reveals an intricate interplay between the structural design of multivalent agents and their biological activities toward protein surfaces.

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.

The expanding field of boron clusters has attracted continuous theoretical efforts to understand their diverse structures and unique bonding. We recently discovered a new reversible redox event of B12(O-3-methylbutyl)12 in which the superoxidized radical cationic form [B12(O-3-methylbutyl)12]•+ was identified and isolated for the first time. Herein, comprehensive (TD-)DFT studies in tandem with electrochemical experiments were employed to demonstrate the generality of the reported behavior across perfunctionalized B12(OR)12 clusters (R = aryl or alkyl). While the spin density of radical cationic clusters is delocalized in the core region, the oxidation brings about notable gains of positive partial charges on the supporting groups whose electronics can readily tune the redox potential of the 0/•+ couple. The underlying changes of frontier orbitals were elucidated, and the resulting [B12(OR)12]•+ species manifest a general diagnostic absorption as a consequence of mixed local/charge-transfer excitations.

Over the past several years, a number of strategies for the functionalization of dicarba-closo-dodecaboranes (carboranes) have emerged. Despite these developments, B - N bond formation on the carborane scaffold remains a challenge due to the propensity of strong nucleophiles to partially deboronate the parent closo-carborane cluster into the corresponding nido form. Here we show that azide, sulfonamide, cyanate, and phosphoramidate nucleophiles can be straightforwardly cross-coupled onto the B(9) vertices of the o- and m-carborane core from readily accessible precursors without significant deboronation by-products, laying the groundwork for further study into the utility and properties of these new B-aminated carborane species. We further showcase select reactivity of the installed functional groups highlighting some unique features stemming from the combination of the electron-donating B(9) position and the large steric profile of the B-connected carborane substituent.

© 2019 American Chemical Society. We report a class of perfunctionalized dodecaborate clusters that exhibit stability during galvanostatic cycling. These boron clusters afford several degrees of freedom in material design to tailor properties including solubility and redox potential. The exceptional stability of these clusters was demonstrated by using a symmetric flow cell setup for electrochemical cycling between two oxidation states for 45 days, with post-run analysis showing negligible decomposition of the active species (

Synthetic bioconjugation at cysteine (Cys) residues in peptides and proteins has emerged as a powerful tool in chemistry. Soft nucleophilicity of the sulfur in Cys renders an exquisite chemoselectivity with which various functional groups can be placed onto this residue under benign conditions. While a variety of reactions have been successful at producing Cys-based bioconjugates, the majority of these feature sulfur-carbon bonds. We report Cys-borylation, wherein a benchtop stable Pt(II)-based organometallic reagent can be used to transfer a boron-rich cluster onto a sulfur moiety in unprotected peptides forging a boron-sulfur bond. Discovered Cysborylation proceeds at room temperature and is tolerant to a variety of functional groups present in complex polypeptides. The resultant bioconjugates show no additional toxicity compared to their Cys aryl-based congeners. Finally, we demonstrate how the developed Cys-borylation can enhance the proteolytic stability of the produced peptide bioconjugates while maintaining the binding affinity to a protein target.

Organometallic complexes have recently gained attention as competent bioconjugation reagents capable of introducing a diverse array of substrates to biomolecule substrates. Here, we detail the synthesis and characterization of an aminophosphine-supported Au(III) platform that provides rapid and convenient access to a wide array of peptide-based assemblies via cysteine S-arylation. This strategy results in the formation of robust C‒S covalent linkages and is an attractive method for the modification of complex biomolecules due to the high functional group tolerance, chemoselectivity, and rapid reaction kinetics associated with these arylation reactions. This work expands upon existing metal-mediated cysteine arylation by introducing a class of air-stable organometallic complexes that serve as competent bioconjugation reagents enabling the synthesis of conjugates of higher structural complexity including macrocyclic stapled and bicyclic peptides, as well as a peptide-functionalized multivalent hybrid nanocluster. This organometallic-based approach provides a convenient, one-step method of peptide functionalization and macrocyclization, and has the potential to contribute to efforts directed towards developing efficient synthetic strategies of building new and diverse hybrid peptide-based assemblies of high complexit

Here we show that azide, sulfonamide, cyanate, and phosphoramidate nucleophiles can be straightforwardly cross-coupled onto the B(9) vertices of the o- and m-carborane core from readily accessible precursors without significant deboronation by-products, laying the groundwork for further study into the utility and properties of these new B-aminated carborane species.

High affinity guest have been reported for the macrocyclic host cucurbit[7]uril (CB[7]), enabling widespread applications, but preventing CB[7] materials from being returned to their guest-free state for reuse. Here we present polyhedral boron clusters (carboranes) as strongly-binding, yet easily removable, guests for CB[7]. Aided by a Pd-catalyzed coupling of an azide anion, we prepared boron-functionalized 9-amino and 9-ammonium modified ortho-carboranes that bind to CB[7] with a Ka=1010 M-1. Upon treatment with base, the ortho-carboranes readily undergo deboronation to yield anionic nido-carborane, a poor guest of CB[7], facilitating recovery of guest-free CB[7]. We showcase the utility of the modified ortho-carborane guest by recycling a CB[7]-functionalized resin. With this report, we introduce stimuli-responsive decomplexation as an additional consideration in the design of high affinity host-guest complexes.

Carrier mobility in doped conjugated polymers is limited by Coulomb interactions with dopant counterions. This complicates studying the effect of the dopant's oxidation potential on carrier generation because different dopants have different Coulomb interactions with polarons on the polymer backbone. Here, dodecaborane (DDB)‐based dopants are used, which electrostatically shield counterions from carriers and have tunable redox potentials at constant size and shape. DDB dopants produce mobile carriers due to spatial separation of the counterion, and those with greater energetic offsets produce more carriers. Neutron reflectometry indicates that dopant infiltration into conjugated polymer films is redox‐potential‐driven. Remarkably, X‐ray scattering shows that despite their large 2‐nm size, DDBs intercalate into the crystalline polymer lamellae like small molecules, indicating that this is the preferred location for dopants of any size. These findings elucidate why doping conjugated polymers usually produces integer, rather than partial charge transfer: dopant counterions effectively intercalate into the lamellae, far from the polarons on the polymer backbone. Finally, it is shown that the IR spectrum provides a simple way to determine polaron mobility. Overall, higher oxidation potentials lead to higher doping efficiencies, with values reaching 100% for driving forces sufficient to dope poorly crystalline regions of the film.

We report our discovery of utilizing perhydroxylated dodecaborate clusters ([B12(OH)12]2-) as a molecular cross-linker to generate a hybrid tungsten oxide material. We further demonstrate how these robust B12-based clusters in the resulting hybrid tungsten oxide material can effectively preserve the specific capacitance up to 4000 cycles and reduce the charge transfer resistance as well as the response time compared to that of pristine tungsten oxide.

While the icosahedral closo-[B12H12]2– cluster does not display reversible electrochemical behavior, perfunctionalization of this species via substitution of all twelve B–H vertices with alkoxy orbenzyloxy (OR) substituents engenders reversible redox chemistry, providing access to clusters in the dianionic,monoanionic, and neutral forms. Here, we evaluated the electrochemical behavior of the electron-rich B12(O-3-methylbutyl)12 (1) cluster and discovered that a new reversible redox event that gives rise to a fourth electronic state is accessible through one-electron oxidation of the neutral species. Chemical oxidation of 1 with [N(2,4-Br2C6H3)3]•+ afforded the isolable[1] •+ cluster, which is the first example of an open-shell cationic B12 cluster in which the unpaired electron is proposed to be delocalized throughout the boron cluster core. The oxidation of 1 is also chemically reversible, where treatment of [1]•+ with ferrocene resulted in its reduction back to 1. The identity of [1]•+ is supported by EPR, UV-vis, multinuclear NMR (1H, 11B), and X-ray photoelectron spectroscopic characterization.

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2, yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Φtotal = 0.07 in oxygen-free cyclohexane. Increased oxygen content in cyclohexane solution quenches the phosphorescence signal. The fluorescent signal intensity remains unaffected by oxygen, suggesting that this molecule could be used as a ratiometric oxygen probe.

Functional handles appended to polymer chain ends are important tools often used as spectroscopic probes for determining polymer structure, affinity labels, and as reactive handles for the conjugation of functional payloads. An easily tunable molecular handle able to carry out multiple functions simultaneously would be of significant use at the polymer, materials, and biology interface. Here, we report the development of carborane-containing chain transfer agents (CTAs, commonly referred to as RAFT agents) which are used in reversible addition–fragmentation chain transfer (RAFT) polymerization. These carborane RAFT agents establish control over polymerization processes leading to monodisperse (Đ = 1.03–1.15) polymers made from N-isopropylacrylamide, styrene, 4-chlorostyrene, and methyl acrylate monomers. The tunable nature of the carborane-based scaffold appended on the polymer chain end serves as a general 1H NMR spectroscopic handle, which can be used to elucidate polymer molecular weight via end-group analysis. Isothermal titration calorimetry (ITC) measurements show that synthesized carborane terminated polymers exhibit strong binding to β-cyclodextrin with an affinity (Ka) of 9.37 × 104 M−1, thereby demonstrating its potential use as an affinity label. Additionally, we show that the free B–H vertices on the carborane RAFT agents exhibit a Raman vibrational signal at ∼2549 cm−1, a Raman-silent region for biological milieu, indicating its potential utility as an innate Raman active probe. The reported carborane RAFT agents bolster the expanding toolbox of molecular probes and serve as tunable platforms for incorporating additional and complementary handles for tailoring chain-end functionality and facilitating polymer analysis.

The synthesis of [1,1’-bis(o-carboranyl)]boranes was achieved through the deprotonation of 1,1’-bis(o-carborane) reagents followed by salt metathesis with ((i)Pr)(2)NBCl(2). X-ray crystallography confirms planar central BC(4) rings and Gutmann-Beckett studies reveal an increase in Lewis acidity at the boron center in comparison to their biphenyl congener, 9-borafluorene.

We report the synthesis of two isomeric Pt(II) complexes ligated by doubly deprotonated 1,1′-bis(o-carborane) (bc). The κ2-C,C-bound isomer (3a) is generated through salt metathesis of K2[bc] and Pt(dtb-bpy)Cl2 (dtb-bpy = 4,4′-di-tert-butyl-2,2′-bipyridine), whereas the κ2-B,C-bound isomer (3b) forms after the addition of K[H-bc] to a reaction mixture containing the Pt(II) starting material and an alkyl lithium reagent. The structures of both isomers were confirmed with 1H NMR spectroscopy and single crystal X-ray crystallography. A cathodic shift is observed for both oxidation (>260 mV) and reduction (∼130 mV) potentials of 3b versus those of 3a, which is corroborated by DFT calculations of both complexes. While photophysical studies reveal similar quantum yields and excited state lifetimes for both isomers, emission spectra for 3b in a PMMA film, frozen solution at 77 K, and as a neat solid are slightly blue-shifted relative to the corresponding emission spectra for 3a. Ultimately, this work provides a ...

This Viewpoint Article describes major advances pertaining to perfunctionalized boron clusters in synthesis and their respective applications. The first portion of this work highlights key synthetic methods allowing one to access a wide range of polyhedral boranes (B4 and B6 – B12 cluster cores) that contain exhaustively functionalized vertices. The second portion of this Viewpoint showcases the historical developments in using these molecules for applications ranging from materials science to medicine. Lastly, we suggest potential new directions for these clusters as they apply to both synthetic methods and applications.

We report the synthesis of air-stable Pd(I) dimer complexes featuring biaryl phosphine ligands. Catalytic experiments suggest that these complexes are comptent precatalysts that can mediate cross-coupling amination reactions between aryl halide electrophiles with both aliphatic and aromatic amine nucleophiles. This work represents an expansion of the air-stable precatalyst toolbox for Pd-catalyzed cross-coupling transformations.

The synthesis of two biscarboranyl (bc) magnesium reagents is described. Treatment of 1,1'-bis(o-carborane) (H2-bc) or 8,8',9,9',10,10',12,12'-octamethyl-1,1'-bis(o-carborane) (H2-Mebc) with Mg(n-Bu)2 in 1,2-dimethoxyethane (DME) affords (bc)Mg(DME)2 (1a-b) as crystalline solids. The magnesium compounds, which have been characterized by NMR spectroscopy and single crystal X-ray crystallography in the case of 1a, serve as competent Grignard-type reagents to generate bc-containing species of tin from Me2SnCl2 (2a-b). The type of substitution of the bis(o-carboranyl) ligand framework is found to strongly effect the electronic character of the tin center, as judged by 119Sn NMR spectroscopy. The disclosed compounds, which are stable solids under an atmosphere of dry nitrogen gas at room temperature, provide a new class of bc-transfer reagents.

Bromination of the luminescent borane, anti-B18H22, via electrophilic substitution using AlCl3 and Br2 yields the monosubstituted derivative 4-Br-anti-B18H21 as an air-stable crystalline solid. In contrast to the unsubstituted parent compound, 4-Br-anti-B18H21 product possesses dual emission upon excitation with UV light and exhibits fluorescence at 410 nm and phosphorescence at 503 nm, with Фtotal = 0.07 in oxygen-free cyclohexane. Increased oxygen content in cyclohexane solution quenches the phosphorescence signal. The fluorescent signal intensity remains unaffected by oxygen, suggesting that this molecule could be used as a ratiometric oxygen probe.

We report the first indirect observation and use of boron vertex-centered carboranyl radicals generated by the oxidation of modified carboranyl precursors. These radical intermediates are formed by the direct oxidation of a B─B bond between a boron cluster cage and an exopolyhedral boron-based substituent (e.g., −BF(3)K, −B(OH)(2)). The in situ generated radical species are shown to be competent substrates in reactions with oxygen-based radicals, dichalcogenides, and N-heterocycles, yielding the corresponding substituted carboranes containing B─O, B─S, B─Se, B─Te, and B─C bonds. Remarkably, this chemistry tolerates various electronic environments, providing access to facile substitution chemistry at both electron-rich and electron-poor B─H vertices in carboranes.

The chloride gradient plays an important role in regulating cell volume, membrane potential, pH, secretion, and the reversal potential of inhibitory glycine and GABAA receptors. Measurement of intracellular chloride activity, $${{\boldsymbol{a}}}_{{\boldsymbol{Cl}}}^{{\boldsymbol{i}}}$$aCli, 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 $${\bf{HC}}{{\bf{O}}}_{{\bf{3}}}^{-}$$HCO3− 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 aCl (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 aCl (1 mM to 100 mM) the potentiometric response of the MC3-ISM is insensitive to $${\bf{HC}}{{\bf{O}}}_{{\bf{3}}}^{-}$$HCO3− or changes in pH. Finally, we demonstrate the biological application of an MC3-ISM by measuring intracellular aCl, and the response to an external Cl-free challenge, for an isolated skeletal muscle fiber.

For decades, chemists have strived to mimic the intricate design and diverse functions of naturally occurring systems through the bioinspired synthesis of programmable inorganic nanomaterials. The development of thiol-capped gold nanoparticles (AuNPs) has driven advancement in this area; however, although versatile and readily accessible, hybrid AuNPs are rarely atomically precise, which limits control over their surface topology and therefore the study of complex structure-function relationships. Here, we present a bottom-up approach to the systematic assembly of atomically precise hybrid nanoclusters employing a strategy that mimics the synthetic ease with which thiol-capped AuNPs are normally constructed, while producing welldefined covalent nanoscale assemblies with diverse surface topologies. For the first time, using a structurally characterized cluster-based organometallic building block, we demonstrate the systematic synthesis of nanoclusters with multivalent binding capabilities to complex protein targets.

Off-cycle processes in catalytic reactions can dramatically influence the outcome of the chemical transformation and affect its yield, selectivity, rate, and product distribution. While the generation of off-cycle intermediates can complicate reaction coordinate analyses or hamper catalytic efficiency, the generation of such species may also open new routes to unique chemical products. Recently, we reported the Pd-mediated functionalization of carboranes with a range of O-, N-, and C-based nucleophiles. By utilizing a Pd-based catalytic system supported by a biaryl phosphine ligand developed by Buchwald and co-workers, we discovered an off-cycle isomerization process (“cage-walking”) that generates four regioisomeric products from a single halogenated boron cluster isomer. Here we describe how several off-cycle processes affect the regioisomer yield and distribution during Pd-catalyzed tandem cage-walking/cross-coupling. In particular, tuning the transmetallation step in the catalytic cycle allowed us to incorporate the cage-walking process into Pd-catalyzed cross-coupling of sterically unencumbered substrates, including cyanide. This work demonstrates the feasibility of using tandem cage-walking/cross-coupling as a unique low-temperature method for producing regioisomers of mono-substituted carboranes.

We report the discovery that a perhydroxylated dodecaborate cluster ([B12(OH)12]2-) can act as an inorganic polyol, serving as a molecular cross-linker in the synthesis of polyurethane-based materials. We further demonstrate how the inherent robustness of the utilized boron cluster can effectively enhance the thermal stability of the produced polyurethane materials incorporating [B12(OH)12]2- building blocks compared to analogous polymers made from carbon-based polyols. Ultimately, this approach provides a potential route to tune the chemical and physical properties of soft materials through incorporation of polyhedral boron-rich clusters into the polymer network.

Redox-active proanions of the type B_(12)(OCH_2Ar)_(12) [Ar = C_6F_5 (1), 4-CF_3C_6H_4 (2), 3,5-(CF_3)_2C_6H_3 (3)] are introduced in the context of an experimental and computational study of the visible-light-initiated polymerization of a family of styrenes. Neutral, air-stable proanions 1–3 were found to initiate styrene polymerization through single-electron oxidation under blue-light irradiation, resulting in polymers with number-average molecular weights (M_n) ranging from ∼6 to 100 kDa. Shorter polymer products were observed in the majority of experiments, except in the case of monomers containing 4-X (X = F, Cl, Br) substituents on the styrene monomer when polymerized in the presence of 1 in CH_2Cl_2. Only under these specific conditions are longer polymers (>100 kDa) observed, strongly supporting the formulation that reaction conditions significantly modulate the degree of ion pairing between the dodecaborate anion and cationic chain end. This also suggests that 1–3 behave as weakly coordinating anions (WCA) upon one-electron reduction because no incorporation of the cluster-based photoinitiators is observed in the polymeric products analyzed. Overall, this work is a conceptual realization of a single reagent that can serve as a strong photooxidant, subsequently forming a WCA.

Summary A cornerstone of modern synthetic chemistry rests on the ability to manipulate the reactivity of a carbon center by rendering it either electrophilic or nucleophilic. However, accessing a similar reactivity spectrum with boron-based reagents has been significantly more challenging. While classical nucleophilic carbon-based reagents normally do not require steric protection, readily accessible, unprotected boron-based nucleophiles have not yet been realized. Herein, we demonstrate that the bench-stable closo-hexaborate cluster anion can engage in a nucleophilic substitution reaction with a wide array of organic and main-group electrophiles. The resulting molecules containing B‒C bonds can be further converted to tricoordinate boron species widely used in organic synthesis.