Field-induced single-molecule magnet behavior in ideal trigonal antiprismatic cobalt(ii) complexes: precise geometrical control by a hydrogen-bonded rigid metalloligand

Abstract

A new cobalt(ii) complex bearing a pair of cobalt(iii) tris-chelate complexes as metalloligands was prepared. The CoII ion possesses an ideal trigonal antiprismatic geometry because of the intermolecular hydrogen-bonds between the metalloligands via counter anions. This complex exhibits slow magnetic relaxation under a dc field reminiscent of a single-molecule magnet behavior.

Stepwise Synthesis, Hydrogen-Bonded Supramolecular Structure, and Magnetic Property of a Co–Mn Heterodinuclear Complex

“…In the heterometallic complex, the Co center took N 3 O 3 octahedral coordination geometry with an average bond distance of ca. 1.90 Å, which is consistent with those of analogous Co III complexes (Table 2) [4,10]. On the other hand, the geometry of the hexacoordinated Mn center was rather ambiguous.…”

“…As the as-synthesized metalloligand takes the mer configuration in 100% yield, the metalloligand underwent mer/fac isomerization upon addition of Mn II ions [10]. This facile isomerization is presumably because of the partial formation of labile [Co II (Himn) 3 ] − owing to the [Co(Himn) 3 ] 0/− redox equilibrium induced by Mn II ions [4]. Thus, we succeeded in designing a Co-Mn heterometallic complex by the metalloligand approach.…”

“…0.1282 (Figure 2, Table 3). The ligand Himn − potentially forms an intermolecular hydrogen-bond in the bidentate coordination mode [4,10] The nonsymmetric coordination geometry of the Mn center resulted in the formation of a supramolecular sheet structure in the ab plane. As mentioned above, many solvent molecules of crystallization were observed in this crystal.…”

“…Discrete cobalt and manganese complexes have been attracting much attention owing to their fascinating magnetic properties such as single-molecule magnet behavior [1][2][3][4][5]. Heteronuclear complexes are strong candidates for such a property because of the magnetic coupling between different paramagnetic metal ions [6].…”

“…Sørensen et al reported an excellent approach in which a C 4 symmetric diamagnetic metalloligand was employed to prepare D 4d symmetric Ln III single-ion magnets [8,9]. In our previous study, we reported a tris-bidentate-chelate cobalt(III) complex as a tridentate metalloligand to obtain a Co III -Co II -Co III mixed-valent complex [4]. The Co II ion in this complex takes ideal D 3d symmetry owing to the rigid C 3 symmetric metalloligand and intermolecular hydrogen bonding interactions.…”