Values of the Mössbauer hyperfine parameters, derived from the least-squares fitting of the ⁵⁷Fe Mössbauer spectra of 1^a.

T (K)	δ (mm s−1)	ΔEQ (mm s−1)	Γ (mm s−1)	Area (%)	Assignment
170	1.19	1.27	0.36	100	Fe(ii), S = 2
80	1.20	1.78	0.25	46	Fe(ii), S = 2
	0.43	0.23	0.25	54	Fe(ii), S = 0
80b	0.35	0.24	0.24	100	Fe(ii), S = 0

^a T is the temperature of measurement, δ is the isomer shift, ΔE_Q is the quadrupole splitting, and Γ is the linewidth. The errors in δ, ΔE_Q, and Γ are ±0.01 mm s⁻¹; the error in area is ±5%.

^bQuench and annealed.