Ligand Hyperfine Interaction in the Complex [Mn(H2O)6] ++ in La2(Mg,Mn)3(NO3)12·24H2O
Abstract The elements of the hyperfine interaction (h.f.i.) between the manganese ion and the protons in the complex [Mn(H2O)6]++ in one of the two possible sites in La2(Mg, Mn)3(NO3)12 · 24 H2O have been measured with ENDOR at 15 to 20 K. The six water molecules in the complex at the chosen site are equivalent for reasons of symmetry.One principal direction of the h.f.i. tensor of each proton is found to be perpendicular to the Mn, O line. With the assumption that each proton is located in the plane of the other two principal directions of its interaction tensor the positions of the protons are evaluated from the anisotropic parts of the h.f.i. tensors. In this calculation the effect of covalency on the anisotropic h.f.i. is ac-counted for with the aid of a simple model.The isotropic h.f.i.'s with the two protons of a water molecule appear to be very nearly equal (+ 0.890 MHz for both). This latter result is remarkable in view of the fact that one proton is distinctly nearer to the manganese ion than the other.