Abstract
Two 3d-4f hetero-metal pentanuclear complexes with the formula {[Cr(III)(2)Ln(III)(3)L(10)(OH)(6)(H(2)O)(2)]Et(3)NH} [Ln=Tb (1), Dy (2); HL=pivalic acid, Et(3)N=triethylamine] have been produced. The metal core of each cluster is made up of a trigonal bipyramid with three Ln(III) ions (plane) and two Cr(III) ions (above and below) held together by six μ(3)-OH bridges. Also reported with this series is the diamagnetic Cr(III)-Y(III) analogue (3). Fortunately, we successfully prepared Al(III)-Ln(III) analogues with the formula {[Al(III)(2)Ln(III)(3)L(10)(OH)(6)(H(2)O)(2)]Et(3)NH⋅H(2)O} [Ln=Tb (4), Dy (5)], containing diamagnetic Al(III) ions, which can be used to evaluate the Cr(III)-Ln(III) magnetic nature through a diamagnetic substitution method. Subsequently, static (dc) magnetic susceptibility studies reveal dominant ferromagnetic interactions between Cr(III) and Ln(III) ions. Dynamic (ac) magnetic susceptibility studies show frequency-dependent out-of-phase (χ'') signals for [Cr(III)(2)Tb(III)(3)] (1), [Cr(III)(2)Dy(III)(3)] (2), and [Al(III)(2)Dy(III)(3)] (5), which are derived from the single-ion behavior of Ln(III) ions and/or the Cr(III)-Ln(III) ferromagnetic interactions.