Synthesis and crystal structure of new organic-based layered perovskites with 2,2′-biimidazolium cations

The reaction of 2,2′-biimidazole with metal diiodides, PbI2 and SnI2, in hydriodic acid affords new organic-based layered perovskites, (C6H8N4)PbI4 and (C6H8N4)SnI4, in which non-primary ammonium organic cations were incorporated with the inorganic layered perovskites. Single crystal X-ray investigations show the aromatic heterocyclic biimidazolium cations form organic layers sandwiched between the metal iodide sheets. The metal iodide perovskite layers exhibit unusual structural features associated with one-dimensional metal halide structures. These structural features are rationalized in terms of stereoactive lone pairs that arise from the weakening of secondary bonds.