A Redox-Switchable Single-Molecule Magnet Incorporating [Re(CN)₇]^3-

Abstract

Reaction of [Re(CN)7]3- (S = 1/2) with 4 equiv of [(PY5Me2)Mn(MeCN)]2+ (S = 5/2) in acetonitrile generates a blue solution containing the cyano-bridged cluster [(PY5Me2)4Mn4Re(CN)7]5+. At room temperature, the color of the reaction rapidly changes from blue to green to yellow, spontaneously generating the one-electron reduced species [(PY5Me2)4Mn4Re(CN)7]4+. Crystal structures show these two clusters share a star-like geometry, wherein four [(PY5Me2)Mn]2+ units are appended to a central, pentagonal bipyramidal [Re(CN)7]3-/4- complex. The dc magnetic properties of the 5+ cluster indicate the presence of ferromagnetic coupling to give an S = 21/2 ground state with an axial zero-field splitting of D = −0.44 cm-1. Ac magnetic susceptibility measurements reveal a spin relaxation barrier of U eff = 33 cm-1, the largest barrier yet observed for a cyano-bridged single-molecule magnet. Upon reduction by one electron, the spin at the Re center is lost and the cluster switches behavior to that of a simple paramagnet containing four noncoupled MnII centers.

Switching Magnetic Properties by a Mechanical Motion

“…A noticeable magnetic property to switch is the Single Molecule Magnet (SMM) behavior. Nevertheless, to the best of our knowledge, only scarce examples have been reported showing extinction of SMM property caused by electrochemical stimulus [34][35][36][37], or photo-induced electron transfer [38].…”

Using EPR to follow reversible dihydrogen addition to paramagnetic clusters of high hydride count: [Rh6(PCy3)6H12]+and [Rh6(PCy3)6H14]+

“…7, 11 There is a more general interest in the redox chemistry and magnetism of transition metal clusters, and a number of examples have been reported of cluster species that support sequential redox events and/or show paramagnetism in isolated species. [12][13][14][15][16][17] For example [W 6 CCl 18 ] n-(n = 0 to 4), 18 [W 6 NCl 18 ] n-(n = 1 to 3), 19 [FeS 8 (PEt 3 ) 6 ] n+ (n = 0 to 4) 20 and [Mo 6 S 8 (PEt 3 ) 6 ] n (n = 1+ to 2-) 21 have been described; while the hexanuclear cluster compounds with edge bridged halide ligands also exhibit extensive redox behaviour, 22-24 and redox pairs such as [Ta 6 Cl 14 (PEt 3 ) 4 ] n+ (n = 0, 1) have been isolated. 25 Up to ten sequential reversible reductions have been reported for the high-nuclearity platinum cluster [Pt 26 (CO) 32 ] n (n = 0 to -10).…”

Exchange Interaction of Strongly Anisotropic Tripodal Erbium Single-Ion Magnets with Metallic Surfaces

“…M olecular magnets 1 offer intriguing features such as slow relaxation of magnetization, 2,3 optical luminescence, 4,5 redox activity, 6,7 and spin crossover. 8 Therefore, such molecules are promising building blocks for multifunctional molecular spintronics applications.…”