Structural‐transformation‐induced Drastic Luminescence Changes in an Organic‐Inorganic Hybrid [ren(cn)4]2− Salt Triggered by Chemical Stimuli

We synthesized a (1‐propylpyridinium) 2 [ReN(CN) 4 ]‐type organic–inorganic hybrid exhibiting water‐vapor‐induced drastic structural changes of the [ReN(CN) 4 ] 2− assemblies. Specifically, upon exposure to water vapor, dehydrated nitrido‐bridged chains were converted to hydrated cyanido‐bridged tetranuclear clusters via rearrangements of large molecular building units in the crystals. These switchable assembly forms display substantially different photo‐physical properties, although in both cases the emission is caused by a metal‐centered d–d transition. The nitrido‐bridged chain exhibited a near‐infrared (749 nm) emission, which blue‐shifted as the temperature increased, while a visible (561 nm) emission and its red shift was demonstrated by the cyanido‐bridged cluster.