High nuclearity cerium–manganese clusters and their structural and magnetic properties: CeIV3MnIII7 and CeIV5MnIII11

Abstract

The syntheses, structures, and magnetic properties are reported of two new high nuclearity Ce–Mn oxo carboxylate clusters at high CeIV/MnIII oxidation states and with nuclearities of Ce5Mn11 and Ce3Mn7. The compounds are (NnBu4)2[Ce5Mn11O13(OH)2(O2CPh)24(NO3)2](NO3) (1) and [Ce3Mn7O8(O2CPh)17(H2O)4] (2). 1 was prepared from the oxidation of Mn(O2CPh)2 by (NnBu4)2Ce(NO3)6, whereas 2 was obtained from the comproportionation reaction of Mn(O2CPh)2 and NnBu4MnO4 in the presence of Ce(NO3)3. Both compounds possess unprecedented structures, comprising an irregular metal topology of several edge-fused triangular units with overall virtual C2 symmetry. Variable-temperature, solid-state dc and ac magnetization studies on 1 and 2 in the 1.8–300K range revealed predominantly weak antiferromagnetic exchange interactions within the complexes. For 1, the combined dc and ac data indicate an S=5 ground state but with low-lying excited states consistent with the high nuclearity. For 2, even lower-lying excited states were observed, precluding clear determination of the ground state but with an estimate of S=2 or 3, or less. Complexes 1 and 2 are new additions to the Ce–Mn family of clusters and the broader class of 3d/4f molecular systems, and 1 is the highest nuclearity Ce–Mn cluster to date.