High‐pressure single‐crystal X‐ray diffraction has been used to trap both the low‐spin (LS) and high‐spin (HS) states of the iron(II) Hofmann spin crossover framework, [FeII(pdm)(H2O)[Ag(CN)2]2⋅H2O, under identical experimental conditions, allowing the structural changes arising from the spin‐transition to be deconvoluted from previously reported thermal effects.

High-pressure single-crystal X-rayd iffraction has been used to trap both the low-spin (LS) and high-spin (HS) states of the iron(II) Hofmann spin crossover framework, [Fe II (pdm)(H 2 O)[Ag(CN) 2 ] 2 ·H 2 O, under identical experimental conditions,allowing the structural changes arising from the spin-transition to be deconvoluted from previously reported thermal effects.Iron(II) spin crossover (SCO) complexes reversibly switch between the low-spin (LS, t 2g 6 e g 0 )a nd high-spin (HS, t 2g 4 e g 2 ) electronic states in response to ac hange in temperature, pressure and irradiation with light. [1][2][3][4][5][6][7][8] TheH S-LS switch involves population-depopulation of the antibonding e g orbitals,t hereby inducing al engthening or shortening of the Fe II À Lb onds by ca. 0.2 .T hese structural changes are transmitted from one active SCO building block to another across the crystal through elastic interactions.Strong coupling between the active building blocks favours cooperative hysteretic behaviour, conferring bistability (memory effect) to the magnetic,optical, electrical, structural and mechanical properties of the material. These properties are promising for