Ex Vivo and In Vivo Evaluation of Dodecaborate-Based Clusters Encapsulated in Ferumoxytol Nanoparticles.

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.

A molecular boron cluster-based chromophore with dual emission.

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.

Sterically Unprotected Nucleophilic Boron Cluster Reagents.

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.

Sonochemical Synthesis of Small Boron Oxide Nanoparticles.

The synthesis of small boron oxide nanoparticles (NPs) is reported. A sonochemical approach in the presence of a capping agent was employed to produce approximately 4-5-nm-sized B2O3 NPs, including the 10B isotopically enriched form. The morphology and composition of the NPs were established using transmission electron microscopy and diffraction, respectively. X-ray photoelectron and Fourier transform infrared spectroscopies provided information about surface functionalization of the B2O3 NPs, which can be further modified through a facile, one-step ligand-exchange process. The toxicity of the synthesized NPs was investigated in Chinese hamster ovarian cells, indicating that these systems were nontoxic up to 1.7 mM concentrations.