Synthesis, Structure, and Magnetism of Heterobimetallic Trinuclear Complexes {[L₂Co₂Ln][X]} [Ln = Eu, X = Cl; Ln = Tb, Dy, Ho, X = NO₃; LH₃ = (S)P[N(Me)N═CH−C₆H₃-2-OH-3-OMe]₃]: A 3d−4f Family of Single-Molecule Magnets

Abstract

Sequential reaction of LH3 (LH3 = (S)P[N(Me)N=CH-C6H3-2-OH-3-OMe]3) with Co(OAc)2 x 4 H2O followed by reaction with lanthanide salts afforded trinuclear heterobimetalllic compounds {[L2Co2Ln][X]} [Ln = Eu (1), X = Cl; Ln = Tb (2), Dy (3), Ho (4), X = NO3] in excellent yields. These compounds retain their integrity in solution as determined by electrospray ionization mass spectrometry studies. The molecular structures of 1-4 were confirmed by a single-crystal X-ray structural study and reveal that these are isostructural. In all of the compounds, the three metal ions are arranged in a perfectly linear manner and are held together by two trianionic ligands, L3-. The two terminal Co(II) ions contain a facial coordination environment (3N, 3O) comprising three imino nitrogen atoms and three phenolate oxygen atoms. The coordination geometry about the cobalt atom is severely distorted. An all-oxygen coordination environment (12O) is present around the central lanthanide ion, which is present in a distorted icosahedral geometry. The coordination sphere around the lanthanide ion is achieved by utilizing three phenolate oxygen atoms and three methoxy oxygen atoms of each ligand. In all of these trinuclear complexes (1-4), the Co-Ln distances are around 3.3 A, while the Co-Co distances range from 6.54 to 6.60 A. The screw-type coordination mode imposed by the ligand induces chirality in the molecular structure, although all of the complexes crystallize as racemates. Magnetic properties of 1-4 have been studied in detail using dc and ac susceptibility measurements. Dynamic measurements reveal that 2-4 display a single-molecule magnet behavior, while the Co2Eu (1) analogue does not show any out-of-phase ac susceptibility.

Trinuclear [CoIII2–LnIII] (Ln=Tb, Dy) Single‐Ion Magnets with Mixed 6‐Chloro‐2‐Hydroxypyridine and Schiff Base Ligands

“…À11 s for known SMMs/SIMs; [4][5][6][7][8][9][10] the U eff value is comparable to that of the star molecule Mn 12 [1] and is remarkably larger than that of the […”

“…The ac oscillating frequencies corresponding to the observed peak temperatures were also fitted to the Arrhenius law, which gave a U eff value of 32.3A C H T U N G T R E N N U N G (2.6) K and a t 0 value of 2.5A C H T U N G T R E N N U N G (1.1) 10 À10 s (Figure 7). The t 0 value is also in the normal range for SMMs/SIMs, [4][5][6][7][8][9][10] but it is remarkably smaller than that of 1 (5.6 10 À6 s), and the U eff value of 2 (32.3 K) is clearly smaller than that of 1 (74.1 K). Further research into the dynamic magnetic behavior of 2 in the form of c'' versus c' plots are shown in Figure 8.…”

“…[2k] Much attention has been paid to the design and construction of pure 4f SMMs/SIMs [4] and 3d-4f SMMs/ SIMs in which manganese, [5] iron, [6] cobalt, [7] nickel, [8] and copper [9] generally act as the 3d metal. Strikingly, although most of the reported lanthanide SIMs are mononuclear complexes, recent research suggested that SIMs could be constructed from a lanthanide ion upon combination with one or more diamagnetic metal ions.…”

“…[5][6][7][8][9][10] [11a] in which the tetranuclear cluster actually shows as a syn-anti acetatebridged dinuclear Dy III 2 magnetic system owing to the diaAbstract: The Schiff base ligand N1,N3-bis(3-methoxysalicylidene)di-A C H T U N G T R E N N U N G ethylenetriamine (H 2 valdien) and the co-ligand 6-chloro-2-hydroxypyridine (Hchp) were used to construct two 3d-4f heterometallic single-ion magnets…”

Intracluster interactions in butterfly{Fe3LnO2}molecules with the non-Kramers ions Tb(III) and Ho(III)

“…The Tb(III) and Ho(III) ions in transition metal clusters have been studied earlier in the context of the search for molecules that show SMM behavior [11][12][13]. Those studies have in common that they were performed using bulk techniques, such as magnetization and ac susceptibility measurements.…”