Fig. 4. Zero-field ⁵⁷Fe Mössbauer spectrum of a microcrystalline sample of 2, recorded at 77 K. The solid line (shown in black) represents the best fit obtained with parameters: δ = 0.48(1) mm s^–1, ΔE_Q = 1.29(1) mm s^–1 (Γ_FWHM,1 = 0.53(1) mm s^–1, Γ_FWHM,2 = 0.42(1) mm s^–1, FWHM = full width at half maximum). The asymmetric doublet was fitted with two quadrupole lines of Lorentzian shape and different linewidths (Γ_FWHM,1/2) but equal integrated area.