A homologous heterospin series of mononuclear lanthanide/TCNQF(4) organic radical complexes

Reactions between trivalent rare earth ions (M-III = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb) and the radical anion of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (TCNQF(4)) produce a family of mononuclear complexes {M[(TCNQF(4))](2)[H2O](x)}center dot(TCNQF(4))(3H(2)O), x = 6, 7. The cationic complex {M-III([TCNQF(4)](-center dot))(2)[H2O](x)}(+) cocrystallizes with one [TCNQF(4)](-center dot) radical anion and three water molecules. One of the coordinated [TCNQF(4)](-center dot) radicals is involved in pi-pi stacking interactions with the uncoordinated [TCNQF(4)](-center dot) radicals which leads to the antiferromagnetic coupling for these ((TCNQF(4))(2))(2-) pi-dimers. The second coordinated [TCNQF(4)](-center dot) remains as a radical ligand and is not involved in pi-pi interactions. Magnetic studies indicate that the Sm compound magnetically orders at 4.4 K and that a fraction of the Gd and Dy samples undergo magnetic ordering at 3.7 K and 4.3 K respectively due to partial dehydration (loss of interstitial water molecules). Diamagnetic metal ions were used to generate magnetically dilute Gd, and Dy compounds that do not exhibit any signs of magnetic ordering.