A cyano-bridged single-molecule magnet: slow magnetic relaxation in a trigonal prismatic MnMo(6)(CN)(18) cluster.

We report the synthesis of the first well-documented example of a cyano-bridged single-molecule magnet. An assembly reaction parallel to that employed in producing the trigonal prismatic [(Me(3)tacn)(6)MnCr(6)(CN)(18)](2+) (Me(3)tacn = N,N',N"-trimethyl-1,4,7-triazacyclononane) cluster affords K[(Me(3)tacn)(6)MnMo(6)(CN)(18)](ClO(4))(3) (1), containing an analogous molybdenum(III)-substituted cluster. Fits to the DC magnetic susceptibility and magnetization data for 1 show that the MnMo(6) cluster possesses weak antiferromagnetic coupling (J = -6.7 cm(-1)), leading to an S = (13)/(2) ground state with significantly enhanced magnetic anisotropy (D = -0.33 cm(-1) and E = -0.018 cm(-1)). Consistent with these results, AC magnetic susceptibility measurements show the molecule to exhibit slow magnetic relaxation indicative of a single-molecule magnet with an energy barrier of 10 cm(-1) for spin reversal.