Magneto-structural studies of an unusual [MnIIIMnIIGdIII(OR)4]4− partial cubane from 2,2′-bis-p-tBu-calix[4]arene

Abstract

Reaction of 2,2′-bis-p-^tBu-calix[4]arene (H₈L) with MnCl₂·4H₂O, GdCl₃·6H₂O and 2,6-pyridinedimethanol (H₂pdm) affords [Mn^IIIMn^IIGd^III(H₃L)(pdmH)(pdm)(MeOH)₂(dmf)]·3MeCN·dmf (3·3MeCN·dmf) upon vapour diffusion of MeCN into the basic dmf/MeOH mother liquor. 3 crystallises in the tetragonal space group P4₁2₁2 with the asymmetric unit comprising the entire cluster. The highly unusual core contains a triangular arrangement of Mn^IIIMn^IIGd^III ions housed within a [Mn^IIIMn^IIGd^III(OR)₄]⁴⁻ partial cubane. Magnetic susceptibility and magnetisation data reveal best fit parameters J_{Mn(II)–Mn(III)} = +0.415 cm⁻¹, J_{Mn(III)–Gd(III)} = +0.221 cm⁻¹, J_{Mn(II)–Gd(III)} = −0.258 cm⁻¹ and D_Mn(III) = −4.139 cm⁻¹. Theoretically derived magnetic exchange interactions, anisotropy parameters, and magneto-structural correlations for 3 are in excellent agreement with the experimental data.