Structural features in some layered hybrid copper chloride perovskites: ACuCl₄ or A₂CuCl₄

We present three new hybrid copper(II) chloride layered perovskites of generic composition ACuCl₄ or A₂CuCl₄, which exhibit three distinct structure types. (m-PdH₂)CuCl₄ (m-PdH₂²⁺ = protonated m-phenylenediamine) adopts a Dion–Jacobson (DJ)-like layered perovskite structure type and exhibits a very large axial thermal contraction effect upon heating, as revealed via variable-temperature synchrotron X-ray powder diffraction (SXRD). This can be attributed to the contraction of an interlayer block, via a slight repositioning of the m-PdH₂²⁺ moiety. (3-AbaH)₂CuCl₄ (3-AbaH⁺ = protonated 3-aminobenzoic acid) and (4-AbaH)₂CuCl₄ (4-AbaH⁺ = protonated 4-aminobenzoic acid) possess the same generic formula as Ruddlesden–Popper (RP) layered perovskites, A₂BX₄, but adopt different structures. (4-AbaH)₂CuCl₄ adopts a near-staggered structure type, whereas (3-AbaH)₂CuCl₄ adopts a near-eclipsed structure type, which resembles the DJ rather than the RP family. (3-AbaH)₂CuCl₄ also displays static disorder of the [CuCl₄]_∞ layers. The crystal structures of each are discussed in terms of the differing nature of the templating molecular species, and these are compared to related layered perovskites. Preliminary magnetic measurements are reported, suggesting dominant ferromagnetic interactions.