Tetra-substituted BDPA radicals via click-chemistry and application to liquid-state DNP

Abstract

The 1,3-bisdiphenylene-2-phenylallyl (BDPA) radical is a promising polarizing agent for DNP NMR, but is limited by poor persistence. A divergent synthetic strategy, using copper(I)-catalyzed azide–alkyne cycloaddition, is presented for preparing tailored BDPA derivatives. A high-molecular-weight, sterically shielded BDPA-dendrimer showed improved persistence and the highest liquid-state DNP enhancement reported thus far.