A family of [MnIII6LnIII2] rod-like clusters

Abstract

Employment of H₃L (= 2-(β-naphthalideneamino)-2-hydroxymethyl-1-propanol) in mixed-metal manganese-lanthanide cluster chemistry has led to the isolation of five new octametallic heteronuclear isostructural [Mn^III₆Ln^III₂] complexes. More specifically, the reaction of Mn(ClO₄)₂·6H₂O with H₃L and the corresponding lanthanide nitrate in MeCN in the presence of a base, NEt₃, yielded four complexes with the general formula [Mn^III₆Ln^III₂O₂(OH)₂(H₂O)₂(HL)₆(NO₃)₆]·6MeCN·0.5H₂O (Ln: Gd, 1·6MeCN·0.5H₂O; Tb, 2·6MeCN·0.5H₂O; Dy, 3·6MeCN·0.5H₂O; Er, 4·6MeCN·0.5H₂O). Furthermore, the Y^III analogue, [Mn^III₆Y^III₂O₂(OH)₂(H₂O)₂(HL)₆(NO₃)₆]·6MeCN·0.5H₂O (5·6MeCN·0.5H₂O), was also synthesized in the same manner. All five clusters describe a central rod-like topology consisting of four face-sharing defective cubane metallic units, forming a planar hexametallic [Mn^III₄Ln^III₂] core, which is further capped by two Mn^III ions. Dc magnetic susceptibility studies in the 5–300 K range for complexes 1–5 reveal the presence of dominant antiferromagnetic exchange interactions within the metallic clusters, while ac magnetic susceptibility measurements show temperature and frequency dependent out-of-phase signals for the Dy^III analogue (3·6MeCN·0.5H₂O), suggesting potential single molecule magnetism character. Furthermore, the Y^III analogue yielded a diamagnetic ground-state for the [Mn^III₆] core, thus proving that the SMM character displayed by 3·6MeCN·0.5H₂O is due to the presence of the Dy^III centres.