Two Heterometallic Nanoclusters [DyIII4NiII8] and [DyIII10MnIII4MnII2]: Structure, Assembly Mechanism, and Magnetic Properties.

ABSTRACT

A full understanding of the assembly mechanisms of coordination complexes is of great importance for a directional synthesis under control. We thus explored here the formation mechanisms of the two new heterometallic nanoclusters [DyIII4NiII8(µ3-OH)8(L)8(OAc)4(H2O)4]·3.25EtOH·4CH3CN (1) and [DyIII10MnIII4MnII2O4(OH)12(OAc)16(L)4(HL)2(EtOH)2]·2EtOH·2CH3CN·2H2O (2) with different cubane-based squarelike ring structures, which were obtained from the reactions of 4-bromo-2-[(2-hydroxypropylimino)methyl]phenol (H2L) with Dy(NO)3·6H2O and the transition metal salt Ni(OAc)2·4H2O or Mn(OAc)2·4H2O. The high-resolution electrospray ionization mass spectrometry (HRESI-MS) tests showed that the skeletons of clusters 1 and 2 have a high stability under the measurement conditions for HRESI-MS. The intermediates formed in the reaction courses of clusters 1 and 2 were tracked using time-dependent HRESI-MS, which helped to determine the proposed hierarchical assembly mechanisms for 1 (H2L → NiL → Ni2L2 → Ni3L4 → Ni4L4 → DyNi4L5 → Dy2Ni6L6 → Dy3Ni6L6 → Dy3Ni7L7 → Dy4Ni8L8) and 2 (H2L → MnL → DyMnL → DyMn2L → Dy2Mn2Lx → Dy8Mn2L2 → Dy10Mn2L2 → Dy10Mn6Lx and H2L → DyL → Dy4L2 → Dy6L2 → Dy8Mn2L2 → Dy10Mn2L2 → Dy10Mn6Lx). This is one of the rare examples of investigating the assembly mechanisms of 3d-4f heterometallic clusters. Magnetic studies indicated that the title complexes both show slow magnetic relaxation behaviors and cluster 1 is a field-induced single-molecule magnet.