Stern−Gerlach Experiments of One-Dimensional Metal−Benzene Sandwich Clusters:  M_n(C₆H₆)_m (M = Al, Sc, Ti, and V)

Abstract

A molecular beam of multilayer metal-benzene organometallic clusters Mn(C6H6)m (M = Al, Sc, Ti, and V) was produced by a laser vaporization synthesis method, and their magnetic deflections were measured. Multidecker sandwich clusters of transition-metal atoms and benzene Scn(C6H6)n+1 (n = 1, 2) and Vn(C6H6)n+1 (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C6H6), Scn(C6H6)n+1, and Vn(C6H6)n+1 are smaller than that of their spin-only values as a result of intracluster spin relaxation, an effect that depends on the orbital angular momenta and bonding characters of the orbitals containing electron spin. While Ti(C6H6)2 was found to be nonmagnetic, Tin(C6H6)n+1 (n = 2, 3) possess nonzero magnetic moments. The mechanism of ferromagnetic spin ordering in M2(C6H6)3 (M = Sc, Ti, V) is discussed qualitatively in terms of molecular orbital analysis. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition-metal atoms are formally zerovalent.

Optical to ultraviolet spectra of sandwiches of benzene and transition metal atoms: Time dependent density functional theory and many-body calculations

“…The neutral analogs have been recently studied by magnetic deflection. 8 The stoichiometries of these clusters led to the proposal of a structure of sandwiches with the M atoms intercalated between benzene units. The magnetism observed in some of them was associated to the spin-coupling along the axis of the sandwich.…”

“…The choice of Ti, V, and Cr is based on: ͑i͒ the experimental evidence that the tendency to form multidecker sandwiches is stronger for the early than for the late transition metals; low-lying electronic states that are coupled to the groundstate through allowed optical transitions; 24 and ͑iii͒ the possibility of comparing the absorption properties of magnetic ͑V n Bz n+1 ͒ and nonmagnetic ͑Ti n Bz n+1 and Cr n Bz n+1 ͒ systems. 8,10 Our aim is to study the changes in the electronic properties, as reflected in the photoabsorption spectrum, as the sandwich size and the metallic element are varied. We find that the optical properties of the sandwiches can be tuned by varying the number of units.…”

Study on Electronic Properties of Composite Clusters toward Nanoscale Functional Advanced Materials

“…In particular, a wide variety of experimental and theoretical efforts have been devoted to the characterization for a multidecker sandwich structure, 19,66,67,96103 because it has been found that M n (Bz) n+1 clusters possess unique size-dependent ferromagnetic properties originating from their one-dimensional structures, where V n (Bz) n+1 clusters exhibit the increase in their magnetic moments monotonically with the cluster size. 28,29 Hence, it is anticipated that they become one of the most promising candidates as building blocks in nanoscale spintronic devices. In order to utilize attractive functional clusters as building blocks in functional materials, however, matrix-isolation at temperatures at or above room temperature is highly desired.…”

“…Considerable experimental and theoretical studies have revealed that the characteristics of the transition metalBz clusters, including geometry, 19,66,97 stability, 67,99 optical 98 and magnetic 28,29,100,101 properties, are highly dependent on the nature of the transition metals in the clusters, in particular, the change in the number of 3d electrons. Figure 14 shows the IRAS spectra in the 6501550 cm ¹1 region after the soft-landing of M(Bz) 2 cation clusters (M = Ti, V, and Cr) onto the n-octadecanethiol SAM (C 18 -SAM) substrates using our soft-landing apparatus as shown in Figure 3.…”

“…18,19 In order to explore the synthesis and characterization of the composite clusters, several experimental methodologies have been developed as shown in Section 2. With the advent of the experimental methods, composite clusters of organometallic sandwich nanoclusters (15 nm length) were generated 1927 and characterized to show novel ferromagnetic electron spin ordering to be the smallest one-dimensional molecular magnets of vanadiumbenzene nanoclusters, 28,29 as described in Sections 3.1 and 3.2. Furthermore, it has been also found that nanoclusters consisting of multicomponents, including silicon and aluminum, can act as novel functional units 18,3036 when the composite nanocluster is well stabilized both geometrically and electronically as a "superatom" 33a,35a as shown in Sections 3.3 and 3.4.…”