A homologous heterospin series of mononuclear lanthanide/TCNQF4organic radical complexes

Abstract

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 (TCNQF₄) produce a family of mononuclear complexes {M[(TCNQF₄)]₂[H₂O]_x}·(TCNQF₄)(3H₂O), x = 6, 7. The cationic complex {M^III([TCNQF₄]⁻˙)₂[H₂O]_x}⁺ cocrystallizes with one [TCNQF₄]⁻˙ radical anion and three water molecules. One of the coordinated [TCNQF₄]⁻˙ radicals is involved in π–π stacking interactions with the uncoordinated [TCNQF₄]⁻˙ radicals which leads to the antiferromagnetic coupling for these ((TCNQF₄)₂)²⁻π-dimers. The second coordinated [TCNQF₄]⁻˙ remains as a radical ligand and is not involved in π–π 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.