Synthesis, characterization and phase transitions in the inorganic–organic layered perovskite-type hybrids [(C n H2n + 1NH3)2PbI4], n = 4, 5 and 6

Three inorganic–organic layered perovskite-type hybrids of the general formula [(C n H 2 n + 1 NH 3 ) 2 PbI 4 ], n = 4, 5 and 6, display a number of reversible first-order phase transitions in the temperature range from 256 to 393 K. [(C 4 H 9 NH 3 ) 2 PbI 4 ] has a single phase transition, [(C 5 H 11 NH 3 ) 2 PbI 4 ] has two phase transitions and [(C 6 H 13 NH 3 ) 2 PbI 4 ] has three phase transitions. In all three cases, the lowest-temperature phase transition is thermochromic and the crystals change colour from yellow in their lowest-temperature phase to orange in their higher-temperature phase for [(C 4 H 9 NH 3 ) 2 PbI 4 ] and [(C 6 H 13 NH 3 ) 2 PbI 4 ], and from orange to red for [(C 5 H 11 NH 3 ) 2 PbI 4 ]. The structural details associated with this phase transition have been investigated via single-crystal X-ray diffraction, SC-XRD, for all three compounds.