Among the coordination compounds, the spin crossover compounds are the most representative examples of the molecular bistability. In this work we are interested by Fe(II) spin crossover compounds which are susceptible to switch between the paramagnetic (high spin S = 2) to diamagnetic (low spin S =0) state and vice versa. This phenomena implies significant magnetic, structural, electrical, chromatic and optical modifications. This open up a plethora of potential applications in the fields of display, memory [1], nanoscience [2] as well as in the other areas... Beside the fact that this phenomenon is known since 1931 [3] and hundreds of compounds were studied, just handful show bistability properties around room temperatures required for device applications [4]. The transition temperature and cooperativity of a SCO system are depending of intermolecular interactions in the crystal lattice and also by molecules themselves [5]. Here we study the influence of different type of interactions on the spin transition properties in few families of Fe(II) compounds. We are interested especially in π-π interactions that are assured by including organic ligands with different number of aromatic rings and different solvents. Also, we show the influence of solvent insertion in the crystal lattice on the intermolecular interactions and transition properties [6]. We observe that the number of aromatic rings involved and different solvents influence differently the cooperativity and transition properties in different classes of studied materials. 1O. Kahn, C. J. Martinez, Science, 1998, 279, 44-48. 2G. Molnar, L. Salmon, W. Nicolazzi, F. Terki, A. Bousseksou, J. Mater. Chem. C, 2014, 2, 1360-1366. 3L. Cambi, A. Gagnasso, Atti. Accad Naz. Lincei, 1931, 13, 809. 4I. Salitros, N. T. Madhu, R. Boca, J. Pavlik, M. Ruben, Monatsh. Chem., 2009, 140, 695-733. 5M. Halcrow, A. Chem. Soc. Rev., 2011, 40, 4119-4142. 6H. J. Shepherd, T. Palamarciuc, P. Rosa, P. Guionneau, G. Molnar, J. F. Letard, A. Bousseksou, Angewandte Chemie International Edition, 2012, V124, Issue 16, 3976- 3980.