Mononuclear Lanthanide Complexes: Energy-Barrier Enhancement by Ligand Substitution in Field-Induced Dy III SIMs

• Published in: Inorganic chemistry 2017-07, Vol.56 (14), p.7985-7997
• Main Authors: Biswas, Sourav, Bejoymohandas, Kochan S, Das, Sourav, Kalita, Pankaj, Reddy, Mundalapudi L P, Oyarzabal, Itziar, Colacio, Enrique, Chandrasekhar, Vadapalli
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/acs.inorgchem.7b00689

The sequential reaction of 2-((6-(hydroxymethyl)pyridin-2-yl)-methyleneamino)phenol (LH ), LnCl ·6H O, and 1,1,1-trifluoroacetylacetone (Htfa) in the presence of Et N afforded [Ln(LH) (tfa) ] [Ln = Dy (1), Ln = Tb (2), and Ln = Gd (3)], while under the same reaction conditions, but in the absence of the coligand, another series of mononuclear complexes, namely, [Ln(LH) ]·Cl·2MeOH] [Ln = Dy (4) and Tb (5)] are obtained. Single-crystal X-ray diffraction analysis revealed that the former set contains a mono-deprotonated [LH] and two tfa ligands, while the latter set comprises of two mono-deprotonated [LH] ligands that are nearly perpendicular to each other at an angle of 86.9°. Among these complexes, 2 exhibited a ligand-sensitized lanthanide-characteristic emission. Analyses of the alternating current susceptibility measurements reveal the presence of single-molecule magnet behavior for 1 and 4, in the presence of direct-current field, with effective energy barriers of 4.6 and 44.4 K, respectively. The enhancement of the effective energy barrier of the latter can be attributed to the presence of a large energy gap between the ground and first excited Kramers doublets, triggered by the change in coordination environments around the lanthanide centers.