The spin crossover (SCO) phenomenon was discovered more than 80 years ago and refers to the transition between high-spin and low spin states for certain metal ions with d4-d7 electronic configurations mainly in octahedral ligand surrounding. This phenomenon is of current interest in molecular magnetism due to the wide range of potential applications of these systems in molecular electronics and spintronics. Among the possible future applications there are data storage, display devices, molecular switches etc. The majority of known SCO compounds contains octahedrally coordinated iron(II) ions. The number of known Co(II) SCO complexes is considerably smaller. In the present contribution the analysis of magnetic and magnetic circular dichroism behavior of the [Co(L-N4 tBu2)(NCS)2] (L-N4 tBu2 = N,N’-Di-tert-butyl-2,11-diaza[3.3](2,6)pyridinophane) compound is given. The compound under study demonstrates low spin to high spin temperature induced spin transition. The observed spin transition is considered as a cooperative phenomenon that is driven by the interaction of the electronic shells of the Co(II) ions with the deformation of the local surrounding that is extended over the crystal lattice via the acoustic phonon field. The model also includes the crystal field of the nearest ligands acting on the Co(II) ion, interelectronic repulsion inside Co(II) ion, spin-orbit and Zeeman interactions. The values of the crystal field parameters are obtained from the analysis of the low temperature magnetic circular dichroism spectrum. In the framework of the presented theoretical approach the experimental magnetic behaviour of the studied compound is explained.