Trinuclear Complexes Derived from R/S Schiff Bases – Chiral Single‐Molecule Magnets

Abstract

The employment of enantiomerically pure Schiff bases in manganese chemistry is revealed to be an excellent method to obtain chiral single-molecule magnets and has allowed the characterization of several pairs of enantiomers, for Eur. J. Inorg. Chem. 2017, 991-998

Chiral LnIII(tetramethylurea)–[WV(CN)8] Coordination Chains Showing Slow Magnetic Relaxation

“…Nowadays scientists make a great effort to develop of new family of single molecule magnets (SMMs) − and single ion magnets (SIMs) ,,− revealing not only high energy barriers and high blocking temperatures − but also other functionalities, such as ferroelectricity, − chirality, ,− luminescence, ,,− and conductivity. − Notably, the introduction of chirality in SMMs provides a great platform for the research of the cross-effect of SMM behavior and nonlinear optical effect of second harmonic generation (SHG), magnetic and natural circular dichroism (MCD and NCD, respectively), ,− and magneto-chiral dichroism (MChD). Nonetheless, the number of these systems is rather low, especially concerning lanthanide assemblies. − Therefore, synthesis of chiral lanthanide complexes is still highly desirable to explore the relationship between their structure and the properties they exhibit.…”

Optical Phenomena in Molecule-Based Magnetic Materials

“…Implementation of chirality into single-molecule magnets (SMMs) was also realized in multimetallic coordination clusters molecules − as well as mononuclear complexes. ,,− In most cases, a straightforward strategy relying on the usage of chiral ligands was explored. For instance, in the cluster-type SMMs, by replacing acetate ligand with ( R )/( S )-chloropropionate, classical {Mn III/IV 12 } nanomagnets turn into a pair of chiral ones showing the opposite Cotton effects in the CD spectra .…”

“…In the case of mononuclear molecular nanomagnets, the prototype SMM of [Tb III (Pc) 2 ] − (Pc – = bis­(phthalocyaninate) anion) can also become chiral when the enantiopure substituent is introduced to the Pc ligand. , Many other chiral lanthanide­(III)-centered SMMs were prepared taking advantage of chiral ligands, such as derivatives of BINOL ([1,1′-binaphthalene]-2,2′-diol), diverse ligands of the Schiff base-type, and others. ,,− Among them, Z. Zhu et al reported a chiral high-performance Dy III SMM which utilizes an enantiopure Schiff base employing (1 R , 2 R )- or (1 S , 2 S )-1,2-bis­(2,4,6-trifluorophenyl)­ethane-1,2-diamine as an equatorial ligand together with triphenyl­silanolate anions as axial ligands (Figure ). The resulting enantiomorphic SMMs exhibit a remarkable anisotropic thermal energy barrier exceeding 1800 K with a high blocking temperature of 20 K. For this compound, the chiral substituent sterically offers a rigid molecular structure leading to perfect axial linearity of O-donor negatively charged silanolate ligands which accounts for the considerably improved SMM characteristics compared with the achiral prototype.…”

Chiral Oxazolidine Complexes Derived from Phenolic Schiff Bases

“…The resulting solution of H 3 L1 was diluted in 100 mL of methanol and employed directly in the subsequent reactions without isolation of the ligands. H 2 L2 was synthesized as previously reported. − …”

“…Recently, our group has developed a research line on coordination compounds derived from Schiff bases, mainly focused on chiral systems starting from enantiopure reactants. − During this period, the reactions of 2-pyridinecarboxaldehyde with TRIS or o -vanillin with enantiomerically pure ( R )- or ( S )-phenylglycinol, designed for the synthesis of Schiff base/azide clusters, allowed us to do the characterization in good yield of the derived oxazolidine complexes containing the ligands H 3 L3 and H 2 L4, instead of the expected H 3 L1 and H 2 L2 bases depicted in Chart . The later ligand, H 2 L4, becomes particularly interesting because, on one hand, the example presented here is the first case in which one oxazolidine has been obtained from this kind of Schiff bases, and, on the other hand, its chiral character leads to selective characterization of two enantiomeric oxazolidines.…”