Molecular Orientation of a Terbium(III)-Phthalocyaninato Double-Decker Complex for Effective Suppression of Quantum Tunneling of the Magnetization.

Tsutomu Yamabayashi,Brian Breedlove,Masahiro Yamashita,Keiichi Katoh

doi:10.3390/molecules22060999

Tsutomu Yamabayashi, Brian Breedlove + Show 2 more

Open Access

https://doi.org/10.3390/molecules22060999

Copy DOI

Abstract

Single-molecule magnet (SMM) properties of crystals of a terbium(III)-phthalocyaninato double-decker complex with different molecular packings (1: TbPc2, 2: TbPc2·CH2Cl2) were studied to elucidate the relationship between the molecular packing and SMM properties. From single crystal X-ray analyses, the high symmetry of the coordination environment of 2 suggested that the SMM properties were improved. Furthermore, the shorter intermolecular Tb–Tb distance and relative collinear alignment of the magnetic dipole in 2 indicated that the magnetic dipole–dipole interactions were stronger than those in 1. This was confirmed by using direct current magnetic measurements. From alternating current magnetic measurements, the activation energy for spin reversal for 1 and 2 were similar. However, the relaxation time for 2 is three orders of magnitude slower than that for 1 in the low-T region due to effective suppression of the quantum tunneling of the magnetization. These results suggest that the SMM properties of TbPc2 highly depend on the molecular packing.

Highlights

Single-molecule magnets (SMMs) have interesting quantum properties, such as slow magnetic relaxation [1,2] and quantum tunneling of magnetization (QTM) [3,4,5]
Considering two components of the ligand field (LF) parameters and the magnetic dipole-dipole (MD) interactions, we focused on two crystal structures of TbPc2 [47,48] with or without crystal solvent molecules
Dc dc energies of the spin states, the QTM rate between ground states was slower, and τ increased. Than it was in an Zeeman splitting, which causes a difference the which causes a difference in the energies of the spin states, the QTM rate between ground statesinwas. These results show that the molecular packing in 2 effectively suppresses QTM via the small energies of the spin states, the rate between ground states was slower, and τ increased

Summary

Introduction

Single-molecule magnets (SMMs) have interesting quantum properties, such as slow magnetic relaxation [1,2] and quantum tunneling of magnetization (QTM) [3,4,5]. Since the discovery of the Mn12 cluster, several compounds showing slow magnetic relaxation have been reported. (LnIII ) complexes have been extensively studied because LnIII ions have a ground state multiplet with large angular momenta, J = L + S, and ligand field (LF) splitting of the ground state gives a large activation energy for spin reversal (Ueff ) compared to polynuclear complexes of transition metal ions [6,7,8,9]. The electronic structure of LnPc2 has been reported by Ishikawa and co-workers [10]. The ground state of the TbIII ions, 7 F6 , which is caused by Russell–Saunders coupling, is mainly split by the strong axial LF around the TbIII ion.

Methods

Results

Conclusion