Structure and magnetic properties of two new lanthanide complexes with the 1-((E)-2-pyridinylmethylidene)semicarbazone ligand
Author(s)
Soek, Rafael Natan
Ferreira, Caroline Mariano
Santana, Francielli Sousa
Hughes, David L.
Date Issued
2019
Type
article
Volume
1184
Start Page
254
End Page
261
Journal
Abstract
Two novel semicarbazone-lanthanide(III) complexes were prepared and structurally characterized as [Ln (Hscpy) 2 (NO 3 ) 2 ]NO 3 ·MeOH (Ln = Gd and Tb; Hscpy = 1-((E)-2-pyridinylmethylidene)semicarbazone). The 4f metal ions experience deca-coordination geometry. Each molecular formula contains two neutral Hscpy molecules in the keto form coordinated through two nitrogen atoms and one oxygen atom, while two nitrate ligands are both coordinated in a chelate mode. The 1 + charge of the cation-complex is balanced by a nitrate anion. Extensive intermolecular hydrogen bonds are formed through the methanol solvate molecule, which acts both as a donor and an acceptor molecule. The chemical composition of the compounds was confirmed by high resolution mass spectra (ESI-MS); peaks at m/z = 122.07 and 148.05, assigned to the fragments C 6 H 8 N 3+ and C 7 H 6 N 3 O + , respectively, are in agreement with the coordination of Hscpy. Alternating current magnetic susceptibility analysis was performed in the 10–10000 Hz range, and the terbium-complex showed slow relaxation of the magnetization when immersed in a static magnetic field of 1 kOe and 1.5 kOe, with an activation barrier to the relaxation (21.9(4) cm −1 ) among the highest found for ten-coordinated Tb(III) complexes. This behavior of slow relaxation of the magnetization is relevant as a memory effect regarding the development of Single Molecule Magnets (SMM).