Abstract
A new synthetic method allows isolating fluoride-bridged complexes Bu(4)N{[M(3NO(2),5Br-H(3)L(1,1,4))](2)(μ-F)} (M = Dy, 1; M = Ho, 2; M = Gd, 3) and Bu(4)N{[Dy(3Br,5Cl-H(3)L(1,2,4))](2)(μ-F)}·2H(2)O, 4·2H(2)O. The crystal structures of 1·5CH(3)C(6)H(5),·2·2H(2)O·0.75THF, 3, and 4·2H(2)O·2THF show that all of them are dinuclear compounds with linear single fluoride bridges and octacoordinated metal centers. Magnetic susceptibility measurements in the temperature range of 2-300 K reveal that the Gd(III) ions in 3 are weakly antiferromagnetically coupled, and this constitutes the first crystallographically and magnetically analyzed gadolinium complex with a fluoride bridge. Variable-temperature magnetization demonstrates a poor magnetocaloric effect for 3. Alternating current magnetic measurements for 1, 2, and 4·2H(2)O bring to light that 4·2H(2)O is an SMM, 1 shows an SMM-like behavior under a magnetic field of 600 Oe, while 2 does not show relaxation of the magnetization even under an applied magnetic field. In spite of this, 2 is the first fluoride-bridged holmium complex magnetically analyzed. DFT and ab initio calculations support the experimental magnetic results and show that apparently small structural differences between 1 and 4·2H(2)O introduce important changes in the dipolar interactions, from antiferromagnetic in 1 to ferromagnetic in 4·2H(2)O.