Ruthenium dimers with multiple bonds between metal atoms: Building blocks for molecule-based magnets

High spin, S = 3/2, ruthenium dimers have proven to be interesting building blocks for molecule-based magnetic materials. Systems containing [RuII/III2(O2CR)4] + form ferrimagnetic two- and three-dimensional (2- and 3-D) network solids, depending upon the R group. An interesting observation from studies of [RuII/III2(O2CMe)4] 3-[Cr(CN)6] is an anomalous constricted hysteresis loop, which has been attributed to the interpenetrated (body centered cubic) structure. Gaining full understanding of this unexpected behavior requires investigation of other interpenetrated materials.;Similar interpenetrated materials Hx[RuII/III 2(O2CMe)4]3-x[Cr(CN)5NO]·zH 2O (x = 0.2; z = 10) and [Ru2(O2CMe)4] 2[Fe(CN)5NO]·H2O have been synthesized. In addition to a constricted hysteresis loop, the [Cr(CN)5NO] 3- species exhibits higher Tc (4 K vs 2.1 K) and smaller unit cell parameters than its S = 1/2 [Fe(CN)6] 3- analog. Another family of interpenetrated materials obtained is [Ru2(O2CH)4]3[MIII(CN) 6] (M = Co, Fe). These materials have smaller unit cell parameters than their acetate analogs and for M = Fe, a greater than 6-fold increase in Tc is observed (13.4 K vs 2.1 K).;In addition to cationic dimers, anionic systems such as [RuII/III 2(CO3)4]3- warrant investigation. Reaction of MII and K3[Ru 2(CO3)4] led to ferrimagnetic HxK 1-xMII[Ru2(CO3) 4](H2O)y(MeOH)z [M = Mn, Fe, Co, Ni, Cu, and Mg] with Tc = 4.2 +/- 0.8 K. All materials, except M = Cu, are isomorphous with orthorhombic 3-D structures composed of linked chains, and mu3-CO32- linkages to both Ru and MII sites, where interactions between [RuII/III2(CO3)4]3- units also results in [RuII/III2(CO 3)4]3- layers bridged by MII sites. A layered motif agrees with nominally identical Tc values, (including S = 0, MgII) as MII plays an important structural role but is not as important in the (through layer) magnetic exchange pathway.;Further investigation of [Ru2(CO3)4] 3- led to LnIII[Ru2(CO3) 4]·8H2O (Ln = Gd, Nd, Ho, Yb), which do not magnetically order above 2K. These materials have a 3-D network structure composed of linked chains with microm-CO3 linkages to Ru and LnIII sites, which is best described as LnIII(OH2)4[Ru 2(CO3)4]1/2[Ru2(CO 3)4(OH2)1/2·3H2O. LnIII-[Ru2(CO3)4] chain interactions, are observed, similar to the MII analog; however Ln materials have mu4-CO3 environments and lack the layered motif as half of the [Ru2(CO3)4]3- sites have axial H2O coordination.