Theoretical Studies on Structural, Magnetic, and Spintronic Characteristics of Sandwiched Eu_nCOT_n+1 (n = 1−4) Clusters

Abstract

Europium (Eu)-cyclootetatrene (COT = C(8)H(8)) multidecker clusters (Eu(n)COT(n+1), n = 1-4) are studied by relativistic density functional theory calculations. These clusters are found to be thermodynamically stable with freely rotatable COT rings, and their total magnetic moments (MMs) increase linearly along with the number of Eu atoms. Each Eu atom contributes about 7 mu(B) to the cluster. Meanwhile, the internal COT rings have little MM contribution while the external COT rings have about 1 mu(B) MM aligned in opposite direction to that of the Eu atoms. The total MM of the Eu(n)COT(n+1) clusters can thus be generalized as 7n - 2 mu(B) where n is the number of Eu atoms. Besides, the ground states of these clusters are ferromagnetic and energetically competitive with the antiferromagnetic states, meaning that their spin states are very unstable, especially for larger clusters. More importantly, we uncover an interesting bonding characteristic of these clusters in which the interior ionic structure is capped by two hybrid covalent-ionic terminals. We suggest that such a characteristic makes the Eu(n)COT(n+1) clusters extremely stable. Finally, we reveal that for the positively charged clusters, the hybrid covalent-ionic terminals will tip further toward the interior part of the clusters to form deeper covalent-ionic caps. In contrast, the negatively charged clusters turn to pure ionic structures.

The bonding characteristics and electronic and magnetic properties of organometallic sandwich clusters and nanowires

“…To date, various organometallic sandwich clusters have been successfully synthesized experimentally and extensively explored theoretically. The possible metal elements include alkali (alkaline‐earth) metals, 3 d ‐transition metals (TM), 4(5) f ‐lanthanide (actinide) metals (Ln); and the organic ligand molecules can be different hydrocarbon cycles C n H n ( n = 3–8) . Particularly, in 1995, Kaya and Nakajima group have synthesized stable linearly multidecked vanadium n –benzene m (V n Bz m , Bz = benzene = C 6 H 6 ) complexes using laser vaporization technique .…”

“…One of the reasons that the metal‐ligand sandwich complexes becomes the hot research topic is their rich physical and chemical properties, which show great potential applications in catalysis, spintronics, optics, molecular recognition, biosensor, and so on. Generally, the metal atoms and ligand molecules form stable sandwich motifs via ionic‐covalent bonding and even pure ionic bonding . More interestingly, Stern–Gerlach magnetic deflection experiments have revealed linear size‐dependent magnetic moments of V n Bz n + 1 ( n = 1–4) clusters and ultrahigh magnetic moments of Eu n COT m (COT = C 8 H 8 = 1,3,5,7‐cyclooctatetraene) .…”

Structures and magnetism of multinuclear vanadium-pentacene sandwich clusters and their 1D molecular wires

“…Many experimental 3-8 and theoretical [9][10][11][12][13][14][15][16][17][18][19][20][21][22] works have reported that a wide variety of organic ligands are able to form stable multidecker sandwich clusters with suitable metals, such as TM-Bz (Bz = benzene, TM = Sc-Ni), 19 and Ln-COT (COT = cyclooctatetraene, Ln = Eu, Tb, Ho, Tm). 8 These clusters exhibit unusual magnetic properties.…”

“…8 These clusters exhibit unusual magnetic properties. For example, the magnetic moment of V n Bz n+1 increases linearly along with the size; 13 Eu n COT n+1 possess extraordinarily high magnetic moments and high spin filter efficiency; 14,23 hybrid TM n (FeCp 2 ) n+1 clusters show significant magnetic moment enhancement as compared to their constituted monometallic counterparts. 15,21,24 In addition, many infinite 1D sandwich molecular wires exhibit exceptional high spin filter efficiency, which are important in the application of spintronics.…”

Boryl‐ and Silyl‐Substituted Mixed Sandwich Compounds of Scandium

“…[5,6] The latter ligand has found widespreadu se in actinidea nd lanthanide chemistry. [12] For instance, the oxidationo fl anthanide sandwich complexes of the form Ln(COT'') 2 resultsi nt he formation of corresponding triple-decker complexes Ln 2 (COT'') 3 . [8] For the furtherd evelopment of this field, functionalized COT ligandshave played akey role.…”