Magnetic properties of molecular compounds of Mn12Ph

We report the magnetic properties of two kinds of new molecular compounds o f Mn12O12(O2CPh)(16)(H2O)(4) (abbreviated as Mn12Ph). (i) The salt of m-N-m ethylpyridinium nitronylnitroxide (abbreviated as m-MPYNN+) and [Mn12Ph](-) was prepared. The EPR spectra of (m-MPYNN+) [Mn12Ph](-) are composed of tw o separate absorptions of m-MPYNN+ and [Mn12Ph](-), indicating that the exc hange interaction between them is negligibly weak. In spite of the weak int eraction, the magnetic relaxation in [Mn12Ph](-) is significantly enhanced in the salt. (ii) The crystal structure and magnetic properties of a solvat ed Mn12Ph, [Mn12Ph]. 2PhCO(2)H, were studied. The crystal includes non-para llel molecular-plane orientations in the unit cell. The single-crystal magn etization curve at 1.7 K shows a hysteresis loop that is very unusual in sh ape. It is found that the curve can be well understood, assuming the presen ce of two domains : the magnetization rotation is frozen in one of the two and is not in the other.