A Family of Mixed-Metal Cyanide Cubes with Alternating Octahedral and Tetrahedral Corners Exhibiting a Variety of Magnetic Behaviors Including Single Molecule Magnetism

Abstract

A series of structurally related pseudocubic metal cyanide clusters of Re(II) and 3d metal ions [{MX}4{Re(triphos)(CN)3}4] (M = Mn, Fe, Co, Ni, Zn; X = Cl, I, -OCH3) have been prepared, and their magnetic and electrochemical properties have been probed to evaluate the effect of changing the identity of the 3d metal ion. Electrochemistry of the clusters reveals several rhenium-based oxidation and reduction processes, some of which result in cluster fragmentation. The richest electrochemistry was observed for the iron congener, which exists as the Re(I)/Fe(III) cluster at the resting potential and exhibits six clear one-electron reversible redox couples and two, closely spaced one-electron quasi-reversible processes. The [{MnIICl}4{ReII(triphos)(CN)3}4] complex exhibits single molecule magnetism with a fast tunneling relaxation process observed at H = 0 determined by micro-SQUID magnetization measurements. A comparative evaluation of the magnetic properties across the series reveals that the compounds exhibit antiferromagnetic coupling between the metal ions, except for [{NiIICl}4{ReII(triphos)(CN)3}4] that shows ferromagnetic behavior. Despite the large ground-state spin value of [{NiIICl}4{ReII(triphos)(CN)3}4] (S = 6), only manganese congeners exhibit SMM behavior to 1.8 K.

An Unprecedented Charge Transfer Induced Spin Transition in an Fe–Os Cluster

“…This difference may be due to weak intra-and intermolecular interactions, [16] most likely related to the packing of the clusters into dimer units. In the dimers, there are p contacts between the tmphen ligands of Fe (1) [19,20] Therefore, the X-ray data indicate that the metal core in 1 is {(LS-Fe II ) 3 Figure 2). …”

Evolvement of molecular nanomagnets in China

“…Owing to the synthetic difficulty of the 4d and 5d compounds, the SMMs based on the heavy metal centres are still very limited compared with the vast amount of 3d analogues [32][33][34][35][36][37][38][39][40]. In this respect, the building block approach, especially using the cyanometalates, was proved to be of crucial importance.…”

A Different 'Spin' on Rhenium Chemistry. Synthetic Approaches and Perspectives of 17-Electron Rhenium Complexes

“…[23,24] In contrast to inorganic medicinal chemistry, paramagnetic rhenium complexes have received some attention in the design of single-molecule magnets (SMM). [19,[25][26][27][28] Here a brief diversion is here needed for a broader perspective. About 20 years ago, the molecular cluster [Mn 12 O 12 (CH 3 CO 2 ) 16 (H 2 O) 4 ] was discovered to exhibit slow magnetic relaxation at low temperatures.…”

“…[33] The strategy of utilizing second-and third-row transition-metal ions in the construction of SMM has been recently and successfully applied for the synthesis of Mo(iii)-based cyanide clusters [34,35] and in one case, for the preparation of a family of mixed-metal cyanide cubes containing octahedral Re(ii) vertices. [27,28,36] Re(ii) complexes, thus, appear as potentially useful building blocks for SMM. However, one of the problems of generating Re(ii) clusters is the lack of a synthetic strategy that allows one to produce Re(ii) precursors in a systematic manner.…”

“…It has been experimentally demonstrated that supramolecular chemistry based on Re(ii) precursors is a powerful entry into the design of molecular materials with tunable magnetic, electronic and photophysical properties. [27,28,36] However, this research requires a steady influx of new precursors and the study of both discrete molecules and their polymeric architecture. It is this fundamental problem that our research wants to tackle.…”