Chiral Molecular Magnets: Synthesis, Structure, and Magnetic Behavior of the Series [M(L‐tart)] (M = Mn^II, Fe^II, Co^II, Ni^II; L‐tart = (2R,3R)‐(+)‐tartrate)

Abstract

A new series of layered magnets with the formula [M(L-tartrate)] (M = Mn(II), Co(II), Fe(II), Ni(II); L-tartrate = (2R,3R)-(+)-tartrate) has been prepared. All of these compounds are isostructural and crystallize in the chiral orthorhombic space group I222, as found by X-ray structure analysis. Their structure consists of a three-dimensional polymeric network in which each metal shows distorted octahedral coordination bound to four L-tartrate ligands, two of which chelate through an alcohol and a carboxylate group and the other two bind terminally through a monodentate carboxylate group. The chirality of the ligand imposes a Delta conformation on all metal centers. Magnetically, the paramagnetic metal centers form pseudotetragonal layers in which each metal is surrounded by four other metals, with syn,anti carboxylate bridges. These salts show intralayer antiferromagnetic or ferromagnetic interactions, depending on the electronic configuration of the metal, and weak interlayer antiferromagnetic interaction. In all cases the magnetic properties are strongly affected by the anisotropy of the system, and the presence of magnetic canting has been found. The Mn derivative behaves as a weak ferromagnet with a critical temperature of 3.3 K. The Ni derivative shows very unusual magnetic behavior in that it exhibits antiferromagnetic ordering below 6 K, the onset of spontaneous magnetization arising from spin reorientation into a canted phase below 4.5 K, and a field-induced ferromagnetic state above 0.3 T at 2 K, behavior typical of metamagnets. The Fe and Co derivatives show antiferromagnetic interactions between spin carriers, but do not order above 2 K.

Crystal structure of catena-poly[diaqua-(μ2-tartrato-κ4 O,O′:O′′,O′′′)cobalt(II)], C4H8CoO8

“…The bond lengths of Co-O range from 2.0128(13) to 2.1400(12) Å, which are similar to those found in other transition-metal complexes of tartrate [4,5]. The angles of O-Co1-O range from 76.37 (5) [7][8][9], the title complex is not forming the dinuclear unit but forms a chain along the c direction. Moreover, the complex crystallizes in the centrosymmetric space group P2 1 /c rather than the chiral one, which probably because the tartrate is generated by the decomposition of oxirane-2,3-dicarboxylic acid.…”

Electroactive Benzothiazole Hydrazones and Their [Mo6O19]2− Derivatives: Promising Building Blocks for Conducting Molecular Materials

“…The C17 À N5 bond length (1.343 (6) ) is intermediate between the single bond observed in most thiazole rings and the double bond in 2, whereas both CÀS bonds (C17ÀS3: 1.714(5), C17ÀS4: Figure 1. Molecular structures of MBTH-H 2 , 2, 4, and 5 (ellipsoids at 50 %).…”

“…[41] Although diazoalkane molybdenum complexes are commonly obtained by condensation of hydrazido complexes with aldehydes or ketones [59] or by reaction of lowvalent molybdenum complexes with diazoalkanes, [60] 2À with a phosphazine, [41] and polyanions 6 a and 7 a reported herein have been obtained by condensation of [Mo 6 O 19 ] 2À with the appropriate hydrazone, AMBTH-H 2 and MBTH-H 2 , respectively, by using a modification of the method devised by Peng for coupling of [Mo 6 O 19 ] 2À with amines. [57] The reaction of (NBu 4 ) 2 A C H T U N G T R E N N U N G [Mo 6 O 19 ] with MBTH-H 2 in refluxing acetonitrile in the presence of dicyclohexylcarbodiimide (DCC) yielded only traces of the expected coupling product 7. However the latter was obtained in reasonable yield (70 %) when dimethylaminopyridine (DMAP) was added to the reaction mixture.…”

“…However the latter was obtained in reasonable yield (70 %) when dimethylaminopyridine (DMAP) was added to the reaction mixture. Compound 6 was similarly obtained by condensation of (NBu 4 ) 2 A C H T U N G T R E N N U N G [Mo 6 O 19 ] with AMBTH-H 2 in refluxing acetonitrile in presence of DCC (1 equiv) and DMAP (0.3 equiv). Negative-mode ESI-MS investigations confirmed the identity of the products (m/z 521.7 for 7 a; m/z 645.6 for 6 a).…”

“…[1,2] One promising way to reach such a target is the bottom-up molecular approach in which different properties are associated through two different molecular networks, such as cationic and anionic sublattices. It allows the coexistence in the material of distinct physical properties, such as conduction, [3][4][5] chirality, [4,6] luminescence, [7] magnetism, [6][7][8][9] and/or spin cross-over. [3,10] Provided that the interactions between these properties (or networks) are strong enough, it may also lead to enhanced or even new properties, as observed for example in the case of the magnetochiral effect.…”