Heterometallic Hexanuclear [Cu<sub>2</sub>Ln<sub>4</sub>] Complexes Showing Zero‐field SMM Behaviour and Magnetocaloric Effect
Arindam Gupta, Sandhya Kapurwan, Siba Prasad Bera, Dibya Jyoti Mondal, Shraoshee Shome, Sanjit Konar
Abstract
Abstract Three heterometallic hexanuclear 3d–4f complexes bearing the formula [Cu 2 (L) 2 Ln 4 (L) 4 (o‐van) 2 ] [L=2‐(( E )‐((2‐hydroxyphenyl)imino]methyl)phenol; o‐van=ortho‐vanillin] (Ln III =Gd III (1), Dy III (2), and Tb III (3)) have been synthesized and characterized. DC magnetic susceptibility measurements reveal overall antiferromagnetic interactions in 1 and 3, whereas co‐existence of ferro‐ as well as antiferromagnetic interactions were observed in 2. The magnetocaloric effect has been observed for 1 with an entropy change (−Δ S m ) of 22.3 J kg −1 K −1 at 3 K and 7 T. Zero‐field single molecule magnet (SMM) behaviour has been observed for 2, where Raman relaxation and quantum tunneling of magnetization (QTM) played a role in magnetization relaxation. The Cu−O−Ln angle well explains the magnetic exchange coupling occurring in the complexes. BS‐DFT calculation for the complexes provides an estimate of the exchange interactions between the paramagnetic centres. Ab initio calculations performed for complex 2 established a good correlation to the experimental relaxation dynamics.