Incorporation of [Co(bpy)3]2+ into the cavities of the three-dimensional oxalate network structure in [Co(bpy)3][LiCr(ox)3] (see picture) produces chemical pressure that destabilises the normal high-spin ground state 4T1 to such an extent that the [Co(bpy)3]2+ complex becomes a spin-crossover complex. It shows a temperature-dependent equilibrium between the 2E low-spin and the 4T1 high-spin states.