Field Induced Single Ion Magnetic Behaviour in Square-Pyramidal Cobalt(II) Complexes with Easy-Plane Magnetic Anisotropy

Amit Mondal,Arpan Mondal,Sanjit Konar

doi:10.3390/magnetochemistry5010012

Amit Mondal, Arpan Mondal + Show 1 more

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https://doi.org/10.3390/magnetochemistry5010012

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Abstract

Two penta-coordinate CoII complexes with formulae [Co(14-TMC)Cl](BF4) (1, 14-TMC = 1,4,8,11-Tetramethyl-1,4,8,11-tetraazacyclotetradecane) and [Co(12-TBC)Cl](ClO4)·(MeCN) (2, 12-TBC = 1,4,7,10-Tetrabenzyl-1,4,7,10-tetraazacyclododecane) were synthesized and characterized. Structural analysis revealed that ligand coordinates to the CoII centre in a tetradentate fashion and the fifth position is occupied by chloride ion and the geometries around CoII centres are best described as distorted square pyramidal. Detailed magnetic measurements disclose the presence of significant easy-plane magnetic anisotropy and field induced slow magnetic relaxation behaviours of the studied complexes. More insight into the magnetic anisotropy has been given using ab initio theory calculations, which agree well with the experimental values and further confirmed the easy-plane magnetic anisotropy.

Highlights

Following the discovery of single-molecule magnet (SMM) behaviour in the well-known Mn12 compound, the number of multinuclear transition metal complexes extended rapidly to probe this phenomenon [1,2,3]
The substantial efforts have been given for the development of both lanthanides based [7,8,9,10] and transition metal based [11,12,13,14,15,16,17,18,19,20,21,22,23,24,25] single ion magnets (SIMs)
The efforts to rationally manipulate the magnetic anisotropy of single ion magnets have been increased [12]

Summary

Introduction

Following the discovery of single-molecule magnet (SMM) behaviour in the well-known Mn12 compound, the number of multinuclear transition metal complexes extended rapidly to probe this phenomenon [1,2,3]. The magnetization data for 1 and 2 have been reached the highest values of 2.33 and 2.45 NμB respectively at 2 K and 7 T (Figure 4b and Supplementary Material Figure S6). It has been found earlier that the difference in slow magnetic relaxation behaviours of mononuclear complexes was mostly because of the different structural distortions around the metal centres [7,8,49,53,54,55] In this present case the differences in ligand system between 1 and 2 brings the structural distortion and promote the elevation of CoII centre which, in turn, gives to substantial spin-orbit coupling and producing different anisotropic and dynamic behaviours

Materials and Methods

Conclusions