Supramolecular Organization and Magnetic Properties of Mesogen-Hybridized Mixed-Valent Manganese Single Molecule Magnets [MnIII8MnIV4O12(Lx,y,z-CB)16(H2O)4

Abstract

Single molecule magnets (SMM) may be considered for the construction of future integrated nanodevices, provided however that some degree of ordering is imparted to these molecules (surfaces nanostructuration). Combining such nanoobjects with liquid-crystalline orderings to control their assembly and to potentially address them individually therefore appears as one promising strategy. Four mesomorphic, mixed-valent [Mn(III)(8)Mn(IV)(4)O(12)(L(x,y,z-CB))(16)(H(2)O)(4)] SMM, differing in the number of liquid-crystalline promoters, (L(x,y,z-CB)), were synthesized, and their self-organizing and magnetic properties were investigated. The influence of the peripheral modifications, and precisely how supramolecular ordering and magnetic properties may be affected by the evolution of the proto-mesogenic cyanobiphenyl-based ligands substitution pattern, was explored. Small-angle X-ray scattering studies revealed that all of the hybridized clusters self-organize into room-temperature bilayer smectic phases, mandated by the specific mesogenic functionalization and that the polymetallic cores are further organized according to a short-range pseudo-2D lattice with hexagonal and/or square symmetry. All mesomorphous hybridized dodecamanganese complexes still behave as SMM: they exhibit blocking of the magnetization at about 2.6 K as evidenced by the occurrence of frequency-dependent out-of-phase ac susceptibility signals as well as an opening of the hysteresis cycle with coercive fields varying between 0.13 and 0.6 T, depending on the surface ligands topology. Comparison of the magnetic properties within this series reveals intricate correlations between the structural features of the mesomorphous molecule magnet (i.e., symmetry of the ligands substitution patterns, molecular conformation, average intercluster distances, and respective inclination) with respect to the relative proportion of slow- and fast-relaxing species and the absolute values of the coercive fields.