Single-chain fluorinated Ir-NHC catalysts for efficient SABRE pyruvate hyperpolarization with average residual iridium below 100 ppb.

Signal Amplification By Reversible Exchange (SABRE) delivers rapid and inexpensive NMR signal enhancement using parahydrogen-derived spin order, but biomedical translation requires catalysts that simultaneously deliver high polarization efficiency together with minimal residual metal contamination. Here we introduce a class of single-chain fluorinated Ir-NHC catalysts for SABRE hyperpolarization of [1-13C]pyruvate that addresses this longstanding trade-off. Retention of carbene backbone unsaturation preserves SABRE efficiency, enabling ∼4% 13C polarization with 50% parahydrogen, comparable to the benchmark Ir-IMes catalyst and approximately threefold higher than the previously reported perfluorinated Ir-SIMesF2 system under identical conditions. Combined with redissolution SABRE, aqueous extraction, and fluorinated silica filtration, one of these catalysts, Ir-IMesF1, yields aqueous hyperpolarized solutions containing <100 ppb residual iridium. The resulting aqueous formulations, while not yet suitable for direct biomedical administration, deliver efficient SABRE hyperpolarization and ultra-low residual iridium contamination, enabling real-time monitoring of in vitro pyruvate-to-lactate conversion under partial parahydrogen enrichment.