Crystal Structures of the Perovskite‐Related System A/Rb/Cu(II)/Br (A=BA, Gu, PEA, 5‐AVA, H2en) with Winners, Losers and Compromises – Versatility from 0D to 3D on Different Levels

Abstract By precipitation from aqueous solutions in HBr we have synthesised new ternary compounds of the systems Rb/Cu(II)/Br and A /Cu(II)/Br with the organic cations A =BA, PEA, H 2 en, 5‐AVA. In addition, we have obtained several quaternary compounds A /Rb/CuBr 2 . All of the 11 new compounds represent the first Cu(II) bromides of the corresponding systems. The coordination of Cu 2+ is dominated by corner‐sharing CuBr 6 octahedra, which have four shorter (square‐planar) and two longer distances, due to the Jahn‐Teller effect. There are also representatives with CuBr 4 tetrahedra. The dimensionality ranges from 3D (RbCuBr 3 ), over 2D with single (BA 2 CuBr 4 , PEA 2 CuBr 4 , 5‐AVA 2 CuBr 4 , H 2 enCuBr 4 ,) or double layers (Rb 3 Cu 2 Br 7 , 5‐AVA 2 RbCu 2 Br 7 ), to 0D (Rb 3 CuBr 5 , Gu 2 CuBr 4 ). A layer structure with edge‐sharing octahedra is found in GuCu 2 Br 5 . Unique structures are found for Rb 7 Cu 3 Br 13 , with a linear chain of elongated (4+2) and compressed (2+4) octahedra, and BACuBr 3 , with a chain of edge‐sharing tetrahedra. All compounds were characterised by single crystal XRD.