Non-transient thermo-/photochromism of iodobismuthate hybrids directed by solvated metal cations
Two iodobismuthate-based organic-inorganic hybrids, [M(DMSO)8][Bi2I9] (M = La (1), Bi (2)), have been successfully designed and synthesized by using solvated metal cations as structure-directing agents (SDAs). 1 displays transient high-temperature thermochromism, which is similar to that of the characteristic low-temperature thermochromic properties for bulk bismuth iodide and iodobismuthate hybrids. Differently, 2 exhibits distinguishing non-transient thermochromic properties stimulated by the different temperature range of thermal treatment. More importantly, by comparison of optical inertness of 1, 2 also displays novel photochromic behavior. The completely different thermo-/photo-responsive properties of 1 and 2 are mainly ascribed to the different binding ability of centre metal cations with DMSO molecules, which cause distinct transformation of the inorganic moiety and consequent modulation of band gaps.