PyrroTriPol: a semi-rigid trityl-nitroxide for high field Dynamic Nuclear Polarization

The advent of high-field DNP-enhanced solid-state NMR has brought new challenges in the design of polarizing agents (PA) used to enhance sensitivity. Here, we present a trityl-nitroxide PA family, PyrroTriPol, based on a rigid piperazine linker. These new radicals can be readily synthesized and purified in large quantities. The rigid linker provides improved performance across a broad range of experimental conditions, while requiring reduced microwave power compared to bis-nitroxides.