Macromolecules, Vol.49, No.17, 6163-6172, 2016
Oxime-Bridged Mn-6 Clusters Inserted in One-Dimensional Coordination Polymer
The reaction of MnCl2.4H(2)O with salicylaldoxime (H(2)salox) and the sodium salt of 1,3-bis(carboxypropyl)tetramethyldisiloxane (H2L) in a 1:1:1 molar ratio led to the self-assembly of {[Mn6O2(salox)(6)(H(2)salox)(H2O)(3)(mu-L)]H(2)salox.1.2H(2)O}n, a 1D coordination polymer consisting of hexamanganese(III) salicylaldoximate cluster as secondary building unit (SBU) and tetramethyldisiloxane-based dicarboxylate linker, namely, 1,3-bis(carboxypropyl)tetramethyldisiloxane. The structure of the compound was established by single crystal X-ray diffraction. The Mn(III) clusters consist of two staggered mu(3)-oxo-bridged Mn-3 triangles held together by the oxygen atoms of the oxime groups. Because of JahnTeller distortion, the MnO distances reach 2.5 angstrom for the oxygen atoms located above and below the triangles mean planes. The compound showed a glass transition peak at around 14 degrees C in the differential scanning calorimetry (DSC) curve. The magnetic susceptibility data were fitted with a set of three intracluster antiferromagnetic exchange interaction coupling constants: J(1) = -0.65 cm1, J(2) = -1.5 cm1, and J(3) = -0.9 cm1. The ac magnetic susceptibility measurements in the 25 K temperature range reveal a frequency-dependent behavior indicative of a slow relaxation of magnetization at low temperature. The coexistence of the lypophilic 1,3-bis(propyl)tetramethyldisiloxane moieties and hydrophilic polar SBUs confers to the structure an amphiphilic character. Dynamic light scattering (DLS), small-angle X-ray scattering (SAXS), and transmission (TEM) and scanning (SEM) electron microscopies demonstrate that in dimethylformamide (DMF) the coordination polymer organizes as micelles, whereas in chloroform it tends to form inverse micelles and vesicles.