Freezing of ring-puckering molecular motion and giant dielectric anomalies in metal-organic perovskites.

Pucker up! Metal-organic perovskites containing azetidinium cations, [(CH(2))(3)NH(2)][M(HCOO)(3)] (M = Mn, Cu, Zn), all show a structural phase transition, coupled with the freezing of the ring-puckering molecular motion of azetidinium cations, and an extremely large dielectric anomaly near room temperature. Molecular dynamics simulations showed the freezing of ring-puckering motion of the four-membered-ring azetidinium cation near room temperature.