Structural Disorder in High-Spin {Co(II)(9)W(V)(6)} (Core)-[Pyridine N-Oxides] (Shell) Architectures.

The combinations of Co(II), octacyanidotungstate(V), and monodentate pyridine N-oxide (pyNO) or 4-phenylpyridine N-oxide (4-phpyNO) led to crystallization of novel crystalline phases {Co(II)[Co(II)(8)(pyNO)(12)(MeOH)(12)][W(V)(CN)(8)](6)} (1) and {Co(II)[Co(II)(8)(4-phpyNO)(7)(MeOH)(17)][W(V)(CN)(8)](6)}·7MeOH·(4-phpyNO)(3) (2). In both architectures, metal-cyanide clusters are coordinated by N-oxide ligands in a simple monodentate manner to give the spherical objects of over 1 nm core diameter and about 2.2 nm (1) and 3 nm (2) of the total diameter, terminated with the aromatic rings. The supramolecular architecture is dominated by dense and rich π-π interaction systems. Both structures are characterized by a significant structural disorder in ligand shell, described with the suitable probability models. For 1, the π-π interactions between the pyNO ligands attached to the same metal centers are suggested for the first time. In 2, 4-phpyNO acts as monodentate ligand and as the crystallization molecule. Magnetic studies indicate the high-spin ground state due to the ferromagnetic interactions Co(II)-W(V) through the cyanido bridges. Due to the high symmetry of the clusters, no signature of slow magnetic relaxation was observed. The characterization is completed by solid-state IR and UV-Vis-NIR spectroscopy. The conditions for the stable M(9)M'(6)-based crystals formation are synthetically discussed in terms of the type of capping ligands: monodentate, bridging, and chelating. The potential of the related polynuclear forms toward the magnetism-based functional properties is critically indicated.