Solvent-dependent structures of lanthanide–TCNQ coordination networks and their magnetic properties

Abstract

Lanthanide complexes were prepared with 2,6-diacetylpyridinebis(benzoylhydrazone) (DAPBH2) and 7,7,8,8-tetracyano-p-quinodimethanide (TCNQ•−). The complexes adopted one of two structure types depending on the reaction solvent. The complexes were categorized as Type I (i.e. bis{[2,6-diacetylpyridinebis(benzoylhydrazone)] methanollanthanide(III)}bis(µ2- 7,7,8,8-tetracyanoquinodimethanide(1−))bis(7,7,8,8-tetracyanoquinodimethanide(1−))bis(7,7,8,8-tetracyanoquinodimethanide(1−)) methanol disolvate, [Ln2(DAPBH2)2 (µ2-TCNQ•−)2(TCNQ•−)2(MeOH)2](TCNQ•−)2·2MeOH (Ln = Gd, Tb, or Dy) or Type-II (i.e. [Ln2(DAPBH2)2(µ2-TCNQ•−)2(TCNQ•−)2(EtOH)2] (TCNQ•−)2·solvent (Ln = Tb and Dy, solvent =4EtOH for the Tb and 2EtOH·2CH2Cl2 for the Dy complexes). These two complexes exhibit dramatically different molecular structures and packings. In all complexes, the strong intra- and intermolecular stacking interactions of the TCNQ•− radicals lead to the formation of 1D TCNQ chains. Magnetic susceptibility measurements for Type I and Type II complexes reveal that they exhibit paramagnetic behavior and that their magnetic properties originate from the lanthanide ions alone, owing to the diamagnetic nature of the TCNQ•− stacks.