Tuning the Single-Molecule Magnetism of Dysprosium Complexes by a Redox-Noninnocent Diborane Ligand

Abstract

The lanthanide complexes [Cp*2Ln]­[N,N′-bpyB] (1: Ln = Dy; 3: Ln = Gd; Cp* = pentamethylcyclopentadienyl) and [222-cryptand-K]­[(Cp*2Ln)­(N,N′-bpyB)] (2: Ln = Dy; 4: Ln = Gd) bearing the redox-noninnocent diborane ligand 5,5′-bis­(dimesitylboranyl)-2,2′-bipyridine (bpyB) have been synthesized through selective reduction of bpyB to the radical anion and diamagnetic dianion states with elemental potassium in the presence of [Cp*2Ln]­[BPh4], respectively. Superconducting quantum interference device (SQUID) measurements revealed that the radical anions and the lanthanide ions in 1 and 3 exhibit an antiferromagnetic interaction. Moreover, the effective energy barrier of magnetic relaxation for 1 (18.5(9) K) is much smaller than that for 2 (77.2(5) K) under a 1 kOe field, highlighting the potential of main-group element-based redox-noninnocent ligands in tuning single-molecule magnetism.

Stability and Solution Behavior of [(dpp-Bian)Ln] and [(dpp-Bian)LnX] (Ln = Yb, Tm, or Dy; X = I, F, or N3)

“…For example, they allowed multielectron transfer reactions for trivalent atoms, , bond formation reactions, and C–H bond activation . Lanthanide atoms complexated with redox-active ligands exhibited a number of interesting magnetic properties, − e.g., those of an exchange-coupled lanthanide radical single-molecular magnet and luminescent and electrochemical properties. − That allowed them to be employed as switchable materials, biosensors, − catalysts for controlled copolymerization, and agents for rare-earth element separations …”

Accessing Lanthanide Metallocene Two-Electron Reduction Chemistry Using 2,2′-Bipyridine

“…33−39 Despite these extensive studies of neutral Cp* 2 Ln(bipy) complexes, the only two anionic complexes of the form [Cp* 2 Ln(bipy)] 1− that have appeared in the literature are the gadolinium and dysprosium complexes [Cp* 2 Ln(bipy B )] 1− (bipy B = 5,5′-bis-(dimesitylboronyl)-2,2′-bipyridine) involving a specialized bipyridine ligand. 40 On the basis of their magnetic susceptibilities, these complexes were found to contain Ln(III) ions. The dianionic nature of the bipy ligand in these complexes suggested to us that they might be capable of effecting twoelectron reduction chemistry, thereby serving as "Ln(I)" equivalents and allowing chemistry that would be otherwise inaccessible to currently known lanthanide complexes.…”

“…Although the cyclopentadienyl samarium bipyridine complex, Cp* 2 Sm­(bipy) (Cp* = C 5 Me 5 ), was synthesized from Cp* 2 Sm­(THF) 2 and bipy and published in 1989, its reduction chemistry was not explored at that time . Andersen and co-workers published the Eu and Yb analogues in 2002, which led to numerous studies of the multiconfigurational ground states of complexes of a variety of bipyridines with the Cp* 2 Yb unit. − Despite these extensive studies of neutral Cp* 2 Ln­(bipy) complexes, the only two anionic complexes of the form [Cp* 2 Ln­(bipy)] 1– that have appeared in the literature are the gadolinium and dysprosium complexes [Cp* 2 Ln­(bipy B )] 1– (bipy B = 5,5′-bis-(dimesitylboronyl)-2,2′-bipyridine) involving a specialized bipyridine ligand . On the basis of their magnetic susceptibilities, these complexes were found to contain Ln­(III) ions.…”

Influence of a Lanthanide Ion on the Ni Site of a Heterobimetallic 3d–4f Mabiq Complex

“…23 Recently, several of these mixed-metal systems have also incorporated redox-active ligands, which offers further potential for both catalysis and magnetism. [24][25][26][27][28][29] In the field of transition metal chemistry -through their ability to participate in redox transformations -these ligands act as 'electron storage sites', thereby opening up the reactive possibilities of the complex as a whole. [30][31][32][33] Ligand-based reactivity has not been robustly developed within lanthanide chemistry.…”

“…Recently, several of these mixed-metal systems have also incorporated redox-active ligands, which offers further potential for both catalysis and magnetism. − In the field of transition metal chemistrythrough their ability to participate in redox transformationsthese ligands act as “electron storage sites”, thereby opening up the reactive possibilities of the complex as a whole. − Ligand-based reactivity has not been robustly developed within lanthanide chemistry. However, investigations into 4f complexes with, for example, redox-active Schiff bases and aminophenolate ligands have shown how these ligands can support the formation of reduced lanthanide ions. − Despite the number of reports with either 3d or 4f centers in combination with redox-active ligands, complexes comprising all three groups are surprisingly limited. − Given the evidence for improved magnetic properties in systems with two paramagnetic centers, synthesizing 3d–4f systems comprising redox-active ligandsin which a ligand radical can exist alongside a paramagnetic lanthanideoffers further opportunities to modulate and exploit exchange interactions.…”