However, with the application of a magnetic field (1000 Oe) slow magnetic relaxation was observed in 1-Dy•0.5MeCN, and 1-Yb•0.5MeCN (Figures and). The external fields applied were selected from the field that yielded the slowest relaxation rate that could be accurately fitted to the generalised Debye model. Peaks in the out-of-phase susceptibility (χ″) were observed between 1.9 and 3.0 K for 1-Dy•0.5MeCN, and between 1.8 and 2.8 K for 1-Yb•0.5MeCN. Given the near identical geometries of compounds 1-Dy•0.5MeCN and 1-Yb•0.5MeCN, suggested from continuous SHAPE analysis, slow magnetic relaxation was observed with despite their complementary geometric CF requirements for SMM behaviour (axial environments for Dy 3+ and equatorial environments for Yb 3+ ). Similarly, SMM behaviour with the C3-symmetric Ln(trensal) family where both Dy 3+ and Yb 3+ analogues exhibit slow magnetic relaxation. Slow magnetic relaxation was tested with 1-Gd•0.5MeCN, 1-Tb•0.5MeCN, 1-Ho•0.5MeCN, 1-Er•0.5MeCN, and 1-Tm•0.5MeCN at 2 K with applied fields up to 2000 Oe but no out-of-phase peaks were observed. and. To investigate the dominating relaxation mechanisms, further fitting was performed using the generalised relaxation equation (Equation ):