Fig. 4: EPR spectra and temperature-dependent plots of χ_MT for the crystals of 2²⁺.

a The EPR spectrum of frozen solution of 2²⁺ (1 × 10⁻⁴ mol/l) at 183 K (in black) with simulation (in red). b The EPR spectrum of the powder sample of 2²⁺ at 183 K with the forbidden transition at the half magnetic field. c Temperature-dependent plots of χ_MT for the crystals of 2²⁺ from 2 to 320 K (in black) with the fitting plot via the Bleaney–Bowers equation (in red). d Temperature-dependent plots of χ_MT for the crystals of 1²⁺ from 2 to 320 K.