Synthesis, Structure, Spectroscopic Studies and Magnetic Properties of the Tetrakis(5,7-dichloro-8-quinolinolato)gadolinium(III) Complex

The synthesis and structural characterization of the neutral gadolinium tetrakis-type complex with 5,7-dichloro-8-quinolinolato (H5,7ClQ) ligands, [Gd(5,7ClQ)₂(H5,7ClQ)₂Cl], is reported. The Gd ^III ion is epta coordinated to one chloride ion and to four ligands: two N,O-chelated monoanions and two as zwitterionic (⁺NH and O ^-) monodentate oxygen donors. Electronic and vibrational spectra provide suitable markers to distinguish the presence of deprotonated and protonated ligands. The magnetic behaviour of this compound was investigated and explained by taking into account that π-π stacking interactions between the (H5,7ClQ) ligands give rise to a ferromagnetic interaction between the gadolinium centres. The Gd^III derivatives provide magnetic evidence for the presence of stacking interactions, which are usually undetectable in optically active Er^III derivatives.