Single-crystal spectral and magnetic studies of dichlorotetrakis(thiourea)-iron(II) and -manganese(II)

Abstract

Single-crystal and powder magnetic susceptibilities of dichlorotetrakis(thiourea)-iron(II) and -manganese(II) are reported for the temperature range 4—300 K. Polarized crystal spectra of the iron compound have been recorded at room, liquid N₂, and liquid He temperatures. The results are interpreted within the point-charge crystal-field formalism on the assumption of D_4h symmetry and estimates have been made of the values of Dq, Dt, and Ds and also of the effective spin–orbit coupling coefficient. Ambiguity concerning the signs of the distortion parameters is inherent in the iron(II) system and the results indicate 0·6 < k=ζ/ζ₀ < 0·7,|Dt| < 85 cm^–1, and Ds ca. 1·8 times the magnitude of Dt and of the same (undetermined) sign. Within a ⁶S–⁴G–⁴P basis for the d⁵ manganese(II) system, Ds is irrelevant, and a simple relation between the signs of magnetic anisotropy and Dt emerges: here Dt > 0 cm^–1. Finally, results from these two compounds are compared with those from the nickel(II) and cobalt(II) analogues.