Incorporation of [Co(bpy)₃]²⁺ into the cavities of the three-dimensional oxalate network structure in [Co(bpy)₃][LiCr(ox)₃] 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.