Fig. 3

The variation of interlayer distance and corresponding crystal deformation. a The interlayer distance at 123 K. b The interlayer distance at 393 K. Upon heating from 123 to 393 K, the interlayer distance between CuCl₄²⁻ dianions separated by the Himd⁺ cations in layer A increases from 5.59 to 6.26 Å, while that separated by layer B increases from 5.64 to 6.16 Å. c Photographs of the crystal deformation recorded at 123 K (left) and 403 K (right) upon heating. (The length of scale bar is 0.2 mm.) The thickness of the crystal corresponds to the crystallographic b-axis. d Durability test of the crystal transformation. The inset shows a photograph of the crystal after 20 cycles. The expansion and shrinkage of the crystal thickness were recorded over 20 cycles without significant deterioration in the single-crystal quality