Octahedral connectivity and its role in determining the phase stabilities and electronic structures of low-dimensional, perovskite-related iodoplumbates

We describe a single crystal X-ray diffraction study and computational analysis of three guanidinium (Gua) based low-dimensional iodoplumbates with one edge-sharing and two corner-sharing octahedral connectivities, respectively. (Gua)3PbI5, which is reported for the first time, has a 1D corner-sharing octahedral chain structure. GuaPbI3 adopts a 1D edge-sharing octahedral chain structure in preference to structures that are either 3D and corner-sharing (i.e., perovskite) or 1D and face-sharing. (Gua)2PbI4 exhibits 2D corner-sharing octahedral connectivity in agreement with previous work. Density functional theory calculations are used to gain insight into the relative stabilities of the three polymorphs of GuaPbI3 and to assess how the connectivity and dimensionality of the octahedral framework influence the electronic structure of each of the hybrid perovskites studied.