New Silver(I) Coordination Polymer with Fe-4 Single-Molecule Magnets as Long Spacer

In continuation of our work on supramolecular architectures of single-molecule magnets (SMMs) as a promising strategy in developing their magnetic performance, in this paper we report the synthesis and single crystal X-ray structure of the centered triangular tetrairon(III) SMM, [Fe-4(PhpPy)(2)(dpm)(6)], Fe-4 (Hdpm = dipivaloylmethane, H(3)PhpPy = 2-(hydroxymethyl)-2-(4-(pyridine-4-yl)phenyl)propane-1,3-diol), and its assembly in the coordination polymer {[Fe-4(PhpPy)(2)(dpm)(6)Ag](ClO4)}(n), Fe4Ag, upon reaction with silver(I) perchlorate. Thanks to the presence of the pyridyl rings on the two tripodal ligands, Fe-4 behaves as divergent ditopic linker, and due to the Fe-4:AgClO4 1:1 ratio, Fe4Ag probably possesses a linear arrangement in which silver(I) ions are linearly coordinated by two nitrogen atoms, forming 1D chains whose positive charge is balanced by the perchlorate anions. The stabilization of such a polymeric structure can be ascribed to the long distance between the two donor nitrogen atoms (23.4 angstrom) and their donor power. Fe4Ag shows slow relaxation of the magnetization which follows a thermally activated process with U-eff/k(B) = 11.17(18) K, tau(0) = 2.24(17) 10(-7) s in zero field, and U-eff/k(B) = 14.49(5) K, tau(0) = 3.88(8) 10(-7) s in 1-kOe applied field, in line with what reported for tetrairon(III) SMMs acting as building blocks in polymeric structures.