Strong Equatorial Crystal Field Enhances the Axial Anisotropy and Energy Barrier for Spin Reversal Process in Yb2 SMMs.

Strong Equatorial Crystal Field Enhances the Axial Anisotropy and Energy Barrier for Spin Reversal Process in Yb2 SMMs.
Chemistry. 2020 Oct 21;:
Authors: Konar S, Mondal A
Abstract
The importance of equatorial crystal fields on magnetic anisotropy of ytterbium SMMs is observed for the first time. Herein, we report three similar dinuclear ytterbium complexes of formula [Yb 2 (3-OMe-L) 2 (DMF) 2 (NO 3 ) 2 ]·DMF ( 1 ), [Yb 2 (3-H-L) 2 (DMF) 2 (NO 3 ) 2 ]·DMF·H 2 O ( 2 ) and [Yb 2 (3-NO 3 -L) 2 (DMF) 2 (NO 3 ) 2 ] ( 3 ), [where 3-X-H 2 L= N'-(2-hydroxy-3-X-benzylidene)picolinohydrazide, X = OMe( 1 ), H( 2 ) NO 2 ( 3 )]. The detailed magnetic measurements display the presence of weak antiferromagnetic interaction between the Yb centers and field induced slow relaxation of magnetization in all the complexes. The higher energy barrier for spin reversal was observed for complex 1 (U eff = 50 K) and it dercreases in the order of 2 (47 K) to 3 (40 K). Notably, complex 1 shows a remarkable energy barrier with in the frequency range of 1-850 Hz reported for Yb-based single molecule magnets (SMMs). Further, the ab initio calculations show the higher axial anisotropy and lower QTM (quantum tunneling of magnetization) in the ground state for 1 compared to 2 and 3 . It has also been observed that the presence of strong crystal field in the equatorial plane(when the ∠O1-Yb-O3 bond angle is close to 90º) enhances the axial anisotropy and improve...

Source: Chemistry - October 21, 2020 Category: Chemistry Authors: Konar S, Mondal A Tags: Chemistry Source Type: research