posted on 2016-02-22, 14:10authored byCurtis M. Zaleski, Simon Tricard, Ezra C. Depperman, Wolfgang Wernsdorfer, Talal Mallah, Martin L. Kirk, Vincent L. Pecoraro
The magnetic behavior of the pentanuclear complex of formula MnII(O2CCH3)2[12-MCMnIII(N)shi-4](DMF)6, 1, was investigated using magnetization and magnetic susceptibility measurements both in the solid state and in solution. Complex 1 has a nearly planar structure, made of a central MnII ion surrounded by four peripheral MnIII ions. Solid state variable-field dc magnetic susceptibility experiments demonstrate that 1 possesses a low value for the total spin in the ground state; fitting appropriate expressions to the data results in antiferromangetic coupling both between the peripheral MnIII ions (J = −6.3 cm–1) and between the central MnII ion and the MnIII ones (J′ = −4.2 cm–1). In order to obtain a reasonable fit, a relatively large single ion magnetic anisotropy (D) value of 1 cm–1 was necessary for the central MnII ion. The single crystal magnetization measurements using a microsquid array display a very slight opening of the hysteresis loop but only at a very low temperature (0.04 K), which is in line with the ac susceptibility data where a slow relaxation of the magnetization occurs just around 2 K. In frozen solution, complex 1 displays a frequency dependent ac magnetic susceptibility signal with an energy barrier to magnetization reorientation (E) and relaxation time at an infinite temperature (τo) of 14.7 cm–1 and 1.4 × 10–7 s, respectively, demonstrating the single molecule magnetic behavior in solution.