Lanthanide complexes containing pentadentate s-triazine-based Schiff base ligand: Synthesis, structure and magnetic features

Five mononuclear Ln(III) complexes {Ln = Gd ( 1 ), Tb ( 2 ), Dy ( 3 ), Ho ( 4 ) and Er ( 5 )} of the general composition [Ln(L)(NO 3 )(H 2 O)]⋅solv (solv = H 2 O and/or DMF) were synthesized and thoroughly characterized. The pentadentate H 2 L Schiff base ligand, formed by condensation of 2,4-bishydrazino-6-amino- s -triazine with 3-ethoxysalicylaldehyde, is coordinated to the Ln(III) atoms in the N 3 O 2 donor set in an equatorial plane. The coordination geometry of the central metal atoms is then completed by a bidentate-bonded nitrato ligand and one water molecule, thus forming a biaugmented trigonal prism environment, as follows from the X-ray structure of complex 1 . A detailed magnetic evaluation (static ( dc ) and dynamic ( ac ) data) of complexes 1 – 5 uncovered that they behave as magnetically diluted paramagnetics with weak antiferromagnetic features originating probably in the presence of non-covalent bonding in the solid samples. Only the complexes of Dy ( 3 ) and Er ( 5 ) showed signs of slow relaxation of magnetization with the estimated energy barrier values of U eff = 9.4 (5) K (for 3 ) and U eff = 9.9 (6) K (for 5 ), and relaxation times of τ 0 = 0.25 (8) μs (for 3 ) and τ 0 = 0.45(9) μs (for 5 ). • Mononuclear Ln(III) (Ln = Gd, Tb, Dy, Ho and Er) complexes were synthesized and characterized. • A pentadentate Schiff-base ligand (H 2 L) with an N 3 O 2 donor set was employed. • X-ray structure of complex 1 , i.e. [Gd(L)(NO 3 )(H 2 O)]⋅DMF, was elucidated. • Static and dynamic magnetic data of complexes 1 – 5 were evaluated. • Dy 3+ and Er 3+ complexes revealed slow relaxation of magnetization, i.e. the behaviour of SMM.