Chiral Co-Crystals of (S)- or (R)-1,1′-Binaphthalene-2,2′-diol and Zn₂Dy₂ Tetranuclear Complexes Behaving as Single-Molecule Magnets

Abstract

Co-crystals formed by coordination complex coformers and chiral organic coformers are difficult to obtain. We found that chiral spiroborate anions (S, S)- and (R, R)-bis­(1,1′-binaphthyl-2,2′-diolato)­boron may undergo in situ alcoholysis reactions at room temperature. The generated tetramethoxyborate anions act as terminal ligands to assemble Zn2Dy2 Schiff base tetranuclear complexes, while the other alcoholysis products (S)- and (R)-1,1′-binaphthalene-2,2′-diol ((S)-binol and (R)-binol, respectively) are coformers that co-crystallize with the Zn2Dy2 tetranuclear compound to form chiral co-crystals with magnetic relaxation behavior, namely, {Zn2Dy2(OH)2(LSchiff)2[B­(OCH3)4]2Cl2}·2­((S)- or (R)-binol)·2H2O·MeOH (H2LSchiff = 2-((Z)-(3-((Z)-2-hydroxy-3-methoxybenzylideneamino)­propylimino)­methyl)-6-methoxyphenol, (S)-1: with (S)-binol, and (R)-1: with (R)-binol). They represent the first chiral single-molecule magnet (SMM) eutectics through the co-crystallization of SMMs and chiral organic coformers.

Asymmetric Assembly of Chiral Lanthanide(III) Tetranuclear Cluster Complexes Using Achiral Mixed Ligands: Single-molecule Magnet Behavior and Magnetic Entropy Change

“…In addition, the Cole–Cole curves in the χ″−χ′ plots show partial characteristics of the double magnetic relaxation (Figure S8), which are not surprising because 1 contains Dy 3+ ions in two coordination configurations, and the Cole–Cole plots at 2–14 K could be fitted by the formula containing two Debye functions. ,, The fitting results showed that its α 1 value range is 0.15–0.41 and its α 2 value range is 0.33–0.56 (Table S5). The larger values of α 1 and α 2 may be closely related to the obvious Raman mechanism in the magnetic relaxation process. , There is no open hysteresis loop for 1 at 1.9 K (Figure S9).…”

“…On the other hand, if chirality is introduced into molecular magnets, it will bring valuable physical properties such as nonlinear optics, − ferroelectricity, − and magneto-optical effects, − making them attractive multifunctional molecular materials. The general case is to obtain chiral structured molecule-based magnets by chiral ligand coordination − or even by cocrystallizing with chiral organic molecules . Another more challenging case is to use achiral ligands to spontaneously construct chiral structured molecule-based magnets, which involve helical chirality, Δ/Λ octahedral coordination configuration of transition metal ions, and cooperative orientation of anions and cations in the axial direction .…”

“…The general case is to obtain chiral structured molecule-based magnets by chiral ligand coordination 28−37 or even by cocrystallizing with chiral organic molecules. 38 Another more challenging case is to use achiral ligands to spontaneously construct chiral structured moleculebased magnets, which involve helical chirality, 39 Δ/Λ octahedral coordination configuration of transition metal ions, 40 and cooperative orientation of anions and cations in the axial direction. 41 It is well known that the chirality occurs when different functional groups are attached to the carbon atom in organic chemistry, however, the chirality of cluster SMMs through the asymmetric distribution of different achiral ligands on both sides of the cluster core has never been reported.…”

“…The larger values of α 1 and α 2 may be closely related to the obvious Raman mechanism in the magnetic relaxation process. 38,76 There is no open hysteresis loop for 1 at 1.9 K (Figure S9).…”

Effects of Counterions, Coordination Anions, and Coordination Solvent Molecules on Single-Molecule Magnetic Behaviors and Nonlinear Optical Properties of Chiral Zn2Dy Schiff Base Complexes

“…15,16 Except for very few examples obtained by spontaneous chiral resolution after assembly with achiral ligands, 6,10,17−20 most chiral SMMs derive their chirality directly from bonded chiral ligands 21−31 or even from the chiral organic molecules participating in the cocrystal. 32 However, it is still difficult to obtain chiral SMMs through the coordination of chiral ligands due to the tendency of chiral molecules to spontaneously form racemates in solution. 33 Therefore, it is necessary to explore directed synthesis to obtain chiral SMMs.…”