The role of the picric acid in the hydrated lanthanide derivatives with neutral ligands. Synthesis and X-ray structures of hydrated neodymium, praseodymium and thulium picrate complexes with nicotinamide-N-oxide

Lanthanide(III) complexes with composition Ln(nic)(H2O)n(pic)3(nic) (Ln=Pr, Nd n=8; Tm n=7) (pic=picrate, nic=nicotinamideN-O) were obtained by reaction of the hydrated lanthanide picrate with nicotinamideN-oxide in ethanol. They were characterized by elemental analysis and IR spectra. The molecular structures of Pr, Nd and Tm complexes were established by X-ray crystallography. Different triclinic phases have been detected for the isostructural Nd and Pr derivatives. They are nine coordinated to eight water molecules and a monodentate nic ligand while the apparently isomorphous Tm derivative looses a water molecule with a eight coordination number and a coordination geometry changing from tricapped trigonal prism (Pr, Nd) to square antiprismatic.