Tris complex of FeII2(2'-pyridyl)imidazole has been encapsulated in the supercages of zeolite Y and characterized by using powder XRD, FTIR, Mössbauer spectroscopy, variable temperature magnetization and MAS NMR techniques and results have been compared with those obtained for this complex with ClO4‾ and SO42‾ as anions. At room temperature, the [Fe(pyim)3](ClO4)2 complex exhibited low spin state, while [FeII(pyim)3]SO4 exhibited the existence of both low and high spin states. The encapsulated [FeII(pyim)3]2+ complex exhibited a broad quadrupole doublet characterized by isomer shift, δ=+0.55 mm/s and quadrupole splitting ∆Eq = 1:26 mm/s. The magnetization measurements carried out for the encapsulated [FeII(pyim)3]2+ complex showed a systematic decrease in its values with decreasing temperature down to 75K with no indication of thermal hysteresis effects. These results suggest the existence of a dynamic spin state equilibrium between the high and low spin states for the encapsulated [FeII(pyim)3]2+ complex with time constant comparable to the characteristic Mössbauer time scale of 57Fe nuclei.