New Silver(I) Coordination Polymer with Fe4 Single-Molecule Magnets as Long Spacer

Luca Rigamonti,Carlo Baschieri,Manuela Vaccari,Fabrizio Roncaglia,Alessandra Forni

doi:10.3390/magnetochemistry4040043

Abstract

In continuation of our work on supramolecular architectures of single-molecule magnets (SMMs) as a promising strategy in developing their magnetic performance, in this paper we report the synthesis and single crystal X-ray structure of the centered triangular tetrairon(III) SMM, [Fe4(PhpPy)2(dpm)6], Fe4 (Hdpm = dipivaloylmethane, H3PhpPy = 2-(hydroxymethyl)-2-(4-(pyridine-4-yl)phenyl)propane-1,3-diol), and its assembly in the coordination polymer {[Fe4(PhpPy)2(dpm)6Ag](ClO4)}n, Fe4Ag, upon reaction with silver(I) perchlorate. Thanks to the presence of the pyridyl rings on the two tripodal ligands, Fe4 behaves as divergent ditopic linker, and due to the Fe4:AgClO4 1:1 ratio, Fe4Ag probably possesses a linear arrangement in which silver(I) ions are linearly coordinated by two nitrogen atoms, forming 1D chains whose positive charge is balanced by the perchlorate anions. The stabilization of such a polymeric structure can be ascribed to the long distance between the two donor nitrogen atoms (23.4 Å) and their donor power. Fe4Ag shows slow relaxation of the magnetization which follows a thermally activated process with Ueff/kB = 11.17(18) K, τ0 = 2.24(17) 10−7 s in zero field, and Ueff/kB = 14.49(5) K, τ0 = 3.88(8) 10−7 s in 1-kOe applied field, in line with what reported for tetrairon(III) SMMs acting as building blocks in polymeric structures.

Highlights

Single-molecule magnets (SMMs) [1], thanks to their directionally bistable magnetic moment, have been investigated over the last two decades as nanoscale, chemically tunable entities for encoding binary information
In continuation of our work on supramolecular architectures of single-molecule magnets (SMMs) as a promising strategy in developing their magnetic performance, in this paper we report the synthesis and single crystal X-ray structure of the centered triangular tetrairon(III) SMM, [Fe4(PhpPy)2(dpm)6], Fe4 (Hdpm = dipivaloylmethane, H3PhpPy = 2-(hydroxymethyl)2-(4-(pyridine-4-yl)phenyl)propane-1,3-diol), and its assembly in the coordination polymer {[Fe4(PhpPy)2(dpm)6Ag](ClO4)}n, Fe4Ag, upon reaction with silver(I) perchlorate
As a promising strategy in developing the performance of SMMs by their assembly into coordination networks, in this paper we have described the behavior of a tetrairon(III) cluster, Fe4, as longer spacer (23.4 Å) when coordinating to silver(I) ions, in comparison with what previously observed with a shorter spacer (14.8 Å) of the same family, A [14]

Summary

Introduction

Single-molecule magnets (SMMs) [1], thanks to their directionally bistable magnetic moment, have been investigated over the last two decades as nanoscale, chemically tunable entities for encoding binary information. Despite the low energy barrier of Fe4 SMMs reaching up to 15–17 K, their chemical versatility has been exploited by creating clusters able to sublimate by fluorination of the peripheral β-diketonato ligands [15,16,17] or anchor on gold surfaces by sulfur-rich tripodal ligands [18,19], as well as modulating the spin ground state by selective replacement of the central metal ion with chromium(III) [20,21], vanadium(III) [22], or lanthanide ions [23,24] This family of SMMs has been characterized as single-molecule junction in scanning tunneling microscope (STM) experiments at 0.5 K [25] and through theoretical calculations for its behavior in spin-polarized transport [26], revealing how Fe4 SMMs would be excellent candidates for molecular spintronics devices. Ag+ ions behave as tetrahedral nodes coordinated by four pyridyl nitrogen atoms of Fe4 units, and the cubic crystals, with no overall second-order anisotropy, can be persistently magnetized parallel or antiparallel to the four main diagonals of the unit cell

Methods

Results

Conclusion