Abstract
Three tetranuclear heterometallic Zn-II-Ln(III) complexes of the 30-membered [3+3] hexaimine macrocycle (L-Et)(6-), with general formula Zn(3)(II)Ln(III) (L-Et)(NO3)(2)OAc center dot 5H(2)O (Ln(III) = Dy-III, Er-III, Yb-III), were prepared using our established one-pot synthesis methodology, whereby the individual components of the whole system are poised to assemble themselves into a mixed 3d/f4f macrocyclic system. This uses a 3:1:3:3 reaction of Zn-II acetate, the appropriate Ln(III) nitrate, 1,4-diformy1-2,3-dihydroxybenzene, and 1,2-diaminoethane. These len individual building blocks readily assemble into tetrametallic complexes, analogous to our previously reported examples with larger macrocycles. Identity was confirmed by IR spectroscopy (imine), micro- (C, H, N) and metal- (Zn, Ln) analysis. TGA (solvent content), and mass spectrometry. Magnetic properties were studied down to 2 K and with ac susceptibility measurements were used to check for slow relaxation of the magnetization characteristic of Single-Molecule Magnet (SMM) behavior. As is often the case for single ion systems (only Ln is paramagnetic) no such behavior was observed. However, under an applied dc field, an out-of-phase ac susceptibility signal is seen for all three complexes. We speculate that shrinkage of macrocyclic ring size (30) compared to that of the original Zn-3(II) Dy-III system (33) has led to a less favorable coordination arrangement for the Dy-III and Er-III ions through a change in the imposed coordination environment of the Ln(III) ion.