Spin State of Cobalt(II) 2,6-Bis(pyrazol-3-yl)pyridine Complex with a Redox-Active Ferrocenyl Substituent

The reaction of new 2,6-bis(pyrazol-3-yl)pyridine ligand (L) containing a redox-active ferrocenyl substituent with cobalt(II) salt gave the cobalt(II) complex [Co(L)2](ClO4)2 (I), which was isolated in a pure state and characterized by elemental analysis, NMR spectroscopy, cyclic voltammetry, and X-ray diffraction. According to X-ray diffraction data (CIF file CCDC no. 2049714) and the Evans method, which allows determining the spin state of paramagnetic compounds in solution on the basis of NMR spectra, the cobalt(II) ion in complex I occurs in the high-spin state and does not undergo temperature-induced spin transition in the temperature range of 120–370 K.