Neutral polar hybrid perovskites of [(CH3)2SO][RE(HCOO)3] (RE = Lu and Y): Phase transitions driven by transformation of weak C-HâO interactions

Abstract

Two iso-structural hybrid perovskites of [(CH3)2SO][RE(HCOO)3] for RE3+ = Lu3+ and Y3+ are polar and possess neutral rare earth formate frameworks incorporating dimethyl sulfoxide locating in the framework cavities and coordinating to the RE3+ ions. The materials display reversible phase transitions at 172 K and 138 K for Lu and Y, respectively. The phase transitions are driven by the transformations of weak C-HâO interactions and the gradual twists of the constituents in low temperature, which control the order-disorder states of dimethyl sulfoxide and account for different anisotropic thermal expansion behaviors for the two phases and the characters of dielectric responses.