Synthesis, characterization and phase transitions of the inorganic-organic layered perovskite-type hybrids [(CnH2n+1NH3)(2)PbI4] (n=12, 14, 16 and 18)

The room temperature single-crystal structures of the inorganic-organic layered perovskite-type hybrids of general formula [(CnH2n+ 1NH3)(2)PbI4] (n = 12, 14, 16 and 18) have been determined. The four compounds each display two reversible phase transitions above room temperature, with phases labelled III, II and I. The single-crystal structures of phase II have also been determined. The phase transition from phase III to phase II is a first-order transition and corresponds to a change in the conformation of the alkylammonium chains and a shift of the inorganic layers relative to each other. The phase change from III to II is thermochromic for all compounds, going from a yellow to an orange colour.