Framework and coordination strain in two isostructural hybrid metal-organic perovskites

Monotonic compression of two iso-structural hybrid metal-organic perovskites [DMA]M(HCOO) 3 (M = Co, Ni) has been connected to their structural distortions. The strongest effects of pressure occur in the tilts of the MO 6 octahedra, M-O bond compression, angular distortions within the MO 6 octahedra and small folding between the octahedra and formate units. The anisotropic stronger compression along the trigonal axis is consistent with NH O bonding nearly perpendicular to this direction. Raman spectra indicate a first order solid-state phase transition between 3-5 GPa in both formates, which can be associated with the symmetry breaking induced by the ordering of the Dma cation. Compression of DmaNiFor 3 and DmaCoFor 3 has been investigated by single-crystal X-ray diffraction and Raman spectroscopy.