Molecules based on M(v) (M = Mo, W) and Ni(ii) ions: a new class of trigonal bipyramidal cluster and confirmation of SMM behavior for the pentadecanuclear molecule {NiII[NiII(tmphen)(MeOH)]6[Ni(H2O)3]2[μ-CN]30[WV(CN)3]6}†
Abstract
The preparation, respectively. Magnetic measurements indicate that the ground states for the trigonal bipyamidal clusters are S = 4 as a consequence of ferromagnetic coupling with JW–Ni = 9.5 cm−1, JMo–Ni = 10 cm−1. The pentadecanuclear clusters exhibit ferromagnetic coupling as well, which leads to S = 12 ground states (JW–Ni = 12 cm−1, JMo–Ni = 12.2 cm−1). Reduced magnetization studies on the W–Ni analogues support the conclusion that they exhibit a negative axial anisotropy term; the fits give D values of −0.24 cm−1 for the W2Ni3cluster and D = −0.04 cm−1for the W6Ni9cluster. AC susceptibility measurements indicate the beginning of an out-of-phase signal for the W2Ni3 and the W6Ni9 compounds, but detailed low temperature studies on small crystals by the microSQUID technique indicate that only the pentadecanuclear cluster exhibits hysteresis in accord with SMM behavior. Neither Mo cluster reveals any evidence for slow paramagnetic relaxation at low temperatures.