Different supramolecular architectures in self-assembled praseodymium(III) and europium(III) complexes with rare coordination pattern of salicylaldimine ligand

Abstract

The metal-promoted one-step reaction of 5-methylsalicylaldehyde with 1,3-phenylenediamine in the presence of europium(III) or praseodymium(III) ions produces salicylaldimine complexes containing the N,N′-bis(5-methylsalicylidene)-1,3-phenylenediamine ligand (C22H20N2O2=H2L) as a result of the [2+1] Schiff base condensation. The compounds were characterized by spectroscopic data (ESI-MS, IR, 1H NMR, UV–Vis, luminescence), magnetic measurements, thermogravimetric analysis and X-ray crystallography. The crystal structures of the complexes reveal two different supramolecular architectures: a finite dimer in {[Eu2(μ-C22H20N2O2)2(C22H20N2O2)2(NO3)6]·2CH3CN} complex with a nine-coordinate distorted tricapped trigonal antiprism geometry and an infinite two-dimensional polymer in {[Pr2(μ-C22H20N2O2)4(NO3)6]∞·4CH3CN} complex with ten-coordinate distorted bicapped dodecahedron geometry. The rare cooordinated pattern of salicylaldimine is observed in these complexes in which the potentially tetradentate N2O2 Schiff base acts as undeprotonated monodentate and/or bridging ligands that use exclusively the oxygens as donor atoms with the nitrogen atoms not being involved in coordination.