Irreversible solvent-driven conversion in cyanometalate {Fe2Ni}n (n = 2, 3) single-molecule magnets

Abstract

Two cyano-bridged single-molecule magnets of {Fe(III)(4)Ni(II)(2)} and {Fe(III)(6)Ni(II)(3)} stoichiometry are described via their magnetic properties described in the frame of geometrical core distortions and orientations of their local anisotropy axes.

Structure‐Property Relationships in Tricyanoferrate(III) Building Blocks and Trinuclear Cyanide‐Bridged Complexes

“…The solid‐state infrared spectra of 1 and 2 display high energy and intense ν BH [2507 and 2544 cm –1 ] and ν CN [2044 and 2119 cm –1 ] stretching absorptions, which indicate that coordinated Tp* Me and cyanide ligands are present , , , . The ν CN stretches seen for 1 and 2 are shifted to higher energies in comparison to that seen for [NEt 4 ]CN (2056 cm –1 ) and are in ranges expected for cyanides coordinated to di‐ (2044 cm –1 ) and trivalent (2119 cm –1 ) iron centers, respectively , , , , , , , , . Subsequent treatment of 2 with Ni(ClO 4 ) 2 · 6H 2 O or NiCl 2 · 6H 2 O, followed by either 2,2′‐bipyridine (bpy), tren [tris(2‐aminoethyl)amine], or DETA (diethylenetriamine) affords trinuclear complexes of {[(Tp* Me )Fe III (CN) 3 ] 2 [Ni II (bpy) 2 ]} · 3H 2 O · 4MeOH ( 3 ), {[(Tp* Me )Fe III (CN) 3 ] 2 [Ni II (tren)]} · 2H 2 O · 3MeOH ( 4 ), and {[(Tp* Me )Fe III (CN) 3 ] 2 [Ni II (DETA)(OH 2 )]} · 6H 2 O · MeCN ( 5 ) stoichiometry, respectively.…”

“…Single‐molecule magnets (SMMs) have received considerable attention over the past two decades as their study lies at the interfaces of chemistry, materials, and physics disciplines . Among these are polynuclear complexes derived from cyanometalate anions, whose magnetic anisotropies arise from unquenched orbital angular momentum, a necessary criterion for the creation of an appreciable spin‐reversal energy barrier . Of known cyanide‐based SMMs those containing [(Tp R )Fe III (CN) 3 ] – building blocks, where Tp R is a tridentate poly(pyrazolyl)borate, have seen extensive use in construction of polynuclear complexes that exhibit slow magnetic relaxation , , , …”

“…Pyrazolylborates are an attractive class of fac ‐coordinate ancillary ligands for constructing structurally related families of polynuclear complexes , , , . Through selective chemical substitution the electronic, steric, and solubility properties of the molecular precursors (building blocks) may be systematically altered with atom‐economical precision and efficiency.…”

“…By careful control of stoichiometry and ligand steric demand the numbers and spatial orientations of formed M(µ‐CN)M′ units may be systematically altered and afford materials with tunable magnetic and optical properties, namely those that display slow magnetic relaxation, e.g. single‐molecule magnets,, , , single‐chain magnets,, spin‐crossover, and photoresponsive behavior.…”

“…In polynuclear complexes containing (polypyrazolylborato)tricyanoferrate(III) ions, [(Tp R )Fe III LS (CN) 3 ] – ( S = 1 / 2 ), the doubly degenerate ( 2 E ) spin ground states provide efficient first‐order orbital contributions that lead to appreciable magnetic anisotropy (2.3 ≤ g ≤ 2.9) , , , , . Through deliberate self‐assembly of these building blocks their single‐ion anisotropy properties may be exploited to create polynuclear derivatives that display slow magnetic‐relaxation dynamics.…”