In situ X-ray study of breathing-like effect in interlocked metal-organic nanocages

Using in situ-variable temperature single-crystal X-ray diffraction (VT-SCXRD) and solid-state quantum mechanical (QM) molecular modelling, the structural adaptability of mechanically interlocked M₁₂L₈ metal-organic cages (MOCs) including different guests is reported. Upon heating, the interlocked material shows a different response as a function of the guest's templating behavior, including a swelling and breathing-like effect of the M₁₂L₈ nanocages. The X-ray structures and solid-state QM calculations were used to analyse the energetic aspects related to the stability of the overall architectures. The energy of the 1D chains of interlocked M₁₂L₈ cages is investigated together with the stabilisation energy of M₁₂L₈ cages and M₁₂L₈ chains immersed in the crystalline phases. The role of the N-Zn-N coordination angles and the mechanical bonds in the breathing-like effect and the stability of the interlocked material is discussed.