Field-induced slow magnetic relaxation in chiral seven-coordinated mononuclear lanthanide complexes

Abstract

Four couples of enantiomerically pure chiral seven-coordinated mononuclear lanthanide complexes, [(L(OEt))Dy((R,R)-Salphen)](2)·3H(2)O (1, L(OEt) = [(Cp)Co(P(O)(OEt)(2))(3)], Cp = cyclopentadiene, Salphen = N,N'-1,2-diphenylethylenebis(salicylideneiminato) dianion), [(L(OEt))Dy((S,S)-Salphen)](2)·3H(2)O (2), [(L(OEt))Dy((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (3, Salcy = N,N'-(1,2-cyclohexanediylethylene)bis(salicylideneiminato) dianion), [(L(OEt))Dy((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (4), [(L(OEt))Tb((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (5), [(L(OEt))Tb((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (6), [(L(OEt))Ho((R,R)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (7) and [(L(OEt))Ho((S,S)-5-Cl-Salcy)]·CH(3)OH·1/8H(2)O (8), have been successfully synthesized by using tetradentate chiral salen-type ligands and the Kläui's tripodal ligand of L(OEt). Structural analyses reveal that all compounds have a typical double-decker sandwich structure, and the Ln(iii) ions exhibit a rare seven-coordinated mode, situating in a distorted monocapped triangular prism polyhedron. Circular dichroism (CD) spectra confirm the enantiomeric nature of the optically active complexes and demonstrate that the chirality is successfully transferred from the ligand to the coordination environment of the Ln(iii) ions. Field-induced slow relaxation of the magnetization is observed for complexes 1-4, suggesting that they can be rare chiral single-ion magnets (SIMs) based on the seven-coordinated lanthanide ions.

Square‐Wave Voltammetry as Analytical Tool for Real‐Time Study of Controlled Naproxen Releasing from Cellulose Derivative Materials

“…We presume that the existence of two crystallographically independent Tb III sites is responsible for the two‐step relaxation processes in complex 2 ; a similar trend was also observed in other SMMs/SIMs systems 4d. x, 7i, 18 In addition, the M versus H plot of 2 does not show any hysteresis at 1.9 K (Figure S9).…”

Salen-type mononuclear dysprosium complex displays significant single-molecule magnet performance

“…For all complexes 1–3 , the χ M T values decrease gradually in the temperature range of 300–50 K and then drop sharply in the temperature range of 50–2 K, reaching the minimum value at 2 K, which may be ascribed to the progressive depopulation of the Stark sublevels and/or possible weak antiferromagnetic dipole–dipole interaction between the molecules, although the magnetic anisotropy may partially affect the low temperature susceptibility. 46,47 The static magnetism for complex 1 (Fig. 2a inset) shows a rapid increase at low field followed by a slow linear increase at high field with a maximum of 6.41 μ B at 1.8 K without reaching the expected theoretical saturation value of 10 μ B , and the M versus H curves at different temperatures are non-superimposed, indicating the existence of a significant magnetic anisotropy and/or low-lying excited states in the system.…”

Synthesis, Structural Characterization, and Chiroptical Studies of Bidentate Salen‐Type Lanthanide (III) Complexes

“…Furthermore, the ligand may provide the necessary conditions to sensitize the ion's photo‐ (or electro‐) luminescence . In this context, salen‐type ligands ( N , N '‐bis(salicylidine)diamine) have shown promising properties especially in binding late lanthanides and promoting Near‐IR luminescence of Yb 3+ complexes …”

“…In this structure the salen ligand is twisted (NCCN dihedral angle) by -54°, which is close to the value found on a heteroleptic Dy 3+ complex containing the same ligand. 15…”

“…10 In this context, salen-type ligands (N,N'-bis(salicylidine)diamine) have shown promising properties especially in binding late lanthanides and promoting Near-IR luminescence of Yb 3+ complexes. [11][12][13][14][15] With the exception of La 3+ and Lu 3+ , all Ln 3+ ions induce characteristic paramagnetic NMR shifts, which can be used to determine accurate solution structures. [16][17][18][19] Gd 3+ may induce a relevant contact shift, which is, however, hardly detectable owing to the severe line broadening brought about by this ion.…”