Tris-dioximate cobalt(II) clathrochelates are promising paramagnetic labels owing to the complete isolation of an encapsulated paramagnetic ion and thus the stability of a complex and the independence of its magnetic behavior from the medium. The functionalization of such complexes by six ribbed and two apical substituents gives a room for fine tuning the characteristics of an encapsulated ion to achieve the desired features. At the same time, the choice of the dioximate ribbed groups affects tremendously the magnetic properties of an encapsulated ion, enabling the temperature-dependent spin transition in these complexes (Fig. 1). Surprisingly, the magnetic properties of the spin-crossover complexes in the solution and in the solid state are different: the spin transition in the latter case is gradual and incomplete at 400K, whereas the solution measurements by Evans method and EPR suggest the complexes to be entirely high-spin at as low as 200K, with the spin-crossover’s temperature of about 100K. The stabilization of the low spin state in the solid state can be explained by the cooperative interactions, the result additionally confirmed by the shift of spin crossover curve to the lower temperatures by progressive grinding of the single crystal. The magnetic susceptibility tensor of the high-spin complexes is highly anisotropic, leading to pseudocontact shifts of distant (>2.5 nm) nuclei signals in the NMR spectra, hence paving the way for the use of the cage cobalt(II) complexes as non-covalent paramagnetic tags (Fig.2). figure