Stern-Gerlach Experiments of One-Dimensional Metal-Benzene Sandwich Clusters: M_n(C_6H_6)_m (M = Al, Sc, Ti, and V)

摘要

A molecular beam of multilayer metal-benzene organometallic clusters M_n(C_6H_6)_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 Sc_n(C_6H_6)_(n+1) (n = 1, 2) and V_n(C_6H_6)_(n+1) (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C_6H_6), Sc_n(C_6H_6)_(n+1), and V_n(C_6H_6)_(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(C_6H_6)_2 was found to be nonmagnetic, Ti_n(C_6H_6)_(n+1) (n = 2, 3) possess nonzero magnetic moments. The mechanism of ferromagnetic spin ordering in M_2-(C_6H_6)_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.