Structural and Physical Properties of Two Distinct 2D Lead Halides with Intercalated Cu(II).

Transition metal cation intercalation between the layers of two-dimensional (2D) metal halides is an underexplored research area. In this work we focus on the synthesis and physical property characterizations of two layered hybrid lead halides: a new compound [Cu(O2C-CH2-NH2)2]Pb2Br4 and the previously reported [Cu(O2C-(CH2)3-NH3)2]PbBr4. These compounds exhibit 2D layered crystal structures with incorporated Cu2+ between the metal halide layers, which is achieved by combining Cu(II) and lead bromide with suitable amino acid precursors. The resultant [Cu(O2C-(CH2)3-NH3)2]PbBr4 adopts a 2D layered perovskite structure, whereas the new compound [Cu(O2C-CH2-NH2)2]Pb2Br4 crystallizes with a new structure type based on edge-sharing dodecahedral PbBr5O3 building blocks. [Cu(O2C-CH2-NH2)2]Pb2Br4 is a semiconductor with a bandgap of 3.25 eV. It shows anisotropic charge transport properties with a semiconductor resistivity of 1.44×1010 Ω·cm (measured along the a-axis) and 2.17×1010 Ω·cm (along the bc-plane), respectively. The fabricated prototype detector based on this material showed response to soft low-energy X-rays at 8 keV with a detector sensitivity of 1462.7 μCGy-1cm-2, indicating its potential application for ionizing radiation detection. These encouraging results are discussed together with the results from density functional theory calculations, optical, magnetic, and thermal property characterization experiments.