A MetatlaH Latelli2021-02-102021-02-102019http://dspace.univ-msila.dz:8080//xmlui/handle/123456789/23781spin crossover in binuclear molecule is investigated using an Ising-type model, including the intramolecular vibrations. The spin transition curve of [Fe(bt)(NCS)2]2bpym complex which presents a two-step transition plateau is well described by the above model. We show that the equilibrium low-spin/high-spin temperature Teq is independent of the vibration frequencies of the intermediate state (HS–LS or LS–HS) xLHS. In addition, a large values of LS–LS state vibration frequencies xLLS lead to an evident two-step transition plateau.Spin crossover; Ising-type model; Binuclear molecules; Two-step spin transitionArticle