Single-Crystal-to-Single-Crystal Transformation from δ-(BEDT-TTF)4[OsNOCl5]1.33(C6H5NO2)0.67 to β"-(BEDT-TTF)3[OsNOCl5]

We report on the single-crystal-to-single-crystal transformation occurring over time in a layered organic molecular conductor based on BEDT-TTF. The process is connected with removal of solvent molecules from the complex anion layer resulting in concomitant partial irreversible conversion of the δ-(BEDT-TTF)4[OsNOCl5]1.33(C6H5NO2)0.67 structure to the β"-(BEDT-TTF)3[OsNOCl5] structure. Along with symmetry lowering from I2/a to Р, huge, drastic changes in the conducting BEDT-TTF layer as well as in the anion arrangement are observed, meanwhile crystallinity of the sample is retained. Coexistence of two phases, parent δ and daughter β" in the same crystal helps in the study of their mutual orientation as well as to formulate a mechanism for the structural transformation.