Peripheral site modification in a family of dinuclear [Dy2(hynad)2-6(NO3)0-6(sol)0-2]0/2- single-molecule magnets bearing a {Dy2(μ-OR)2}4+ diamond-shaped core and exhibiting dissimilar magnetic dynamics

The first use of the organic chelate N-hydroxy-1,8-naphthalimide (hynadH) in Dy-III chemistry has unveiled access to a synthetic 'playground' composed of four new dinuclear complexes, all of which possess the same planar {Dy-2(mu-OR)(2)}(4+) diamond-shaped core, resulting from the bridging and chelating capacity of the hynad- groups. The structural stability of the central {Dy-2} core has allowed for the modulation of the peripheral coordination sites of the metal ions, and specifically the NO3-/hynad(-) ratio of capping groups, thus affording the compounds [Dy-2(hynad)(2)(NO3)(4)(DMF)(2)] (1), (Me4N)(2)[Dy-2(hynad)(2)(NO3)(6)] (2), [Dy-2(hynad)(4)(NO3)(2)(H2O)(2)] (3), and [Dy-2(hynad)(6)(H2O)(2)] (4). Because of the chemical and structural modifications in the series 1-4, the Dy-III coordination polyhedra are also dissimilar, comprising the muffin (1 and 3), tetradecahedral (2), and spherical tricapped trigonal prismatic (4) geometries. Complexes 1, 2, and 4 exhibit a ferromagnetic response at low temperatures, while 3 is antiferromagnetically coupled. All compounds exhibit out-of-phase (chi''M) ac signals as a function of ac frequency and temperature, thus behaving as single-molecule magnets (SMMs), in the absence or presence of applied dc fields. Interestingly, the hynad(-)-rich and nitrato-free complex 4, demonstrates the largest energy barrier (U-eff = 69.62(1) K) for the magnetization reversal which is attributed to the presence of the two axial triangular faces of the spherical tricapped trigonal prism by the negatively charged O-atoms of the hynad(-) ligands.