UCLA

This work describes synthetic investigations to rationally tune the redox properties of icosahedral dodecaborate clusters through perfunctionalization of all 12 boron vertices. Functionalization in this manner engenders redox activity of the boron cluster derivatives, with the ability to tune these redox properties as a function of the substituent(s) used. New methods were developed to rapidly produce perfunctionalized boron clusters under ambient conditions, enabling the accelerated preparation of additional cluster derivatives. Several clusters featuring higher redox potentials than any cluster derivatives to date were reported, extending the tunable range of clusters of the type B12(OR)12 to over 1 V for the same redox event. Further modification of the cluster through vertex differentiation by incorporating a single NO2 group created a new class of B12(OR)11NO2 clusters. These vertex differentiated clusters featured redox potentials ~ 0.5 V higher than their B12(OR)12 analogues, demonstrating a further expansion of the tunable redox properties of perfunctionalized boron clusters. After thorough demonstration of the high degree of redox tunability possible with perfunctionalized boron clusters, their extremely stable nature was shown via bulk electrochemical cycling using flow cell battery testing. The B12(OR)12 derivatives tested in a symmetric cell exhibit no observable degradation even after 1000+ hours and ~500 cycles, and a proof-of-concept all boron cluster flow cell battery prototype device showed stable cycling for over a week. In summary, new methods to decorate dodecaborate clusters with a diverse array of functional groups were reported, along with new insights on the significantly expanded available redox potential window for these molecules.