The relation between crystal structure and the occurrence of quantum-rotor-induced polarization.

Among hyperpolarization techniques, quantum-rotor-induced polarization (QRIP), also known as the Haupt effect, is a peculiar one. It is, on the one hand, rather simple to apply by cooling and heating a sample. On the other hand, only the methyl groups of a few substances seem to allow for the effect, which strongly limits the applicability of QRIP. While it is known that a high tunnel frequency is required, the structural conditions for the effect to occur have not been exhaustively studied yet. Here we report on our efforts to heuristically recognize structural motifs in molecular crystals able to allow to produce QRIP.