Experimental and theoretical studies of the structural and electronic properties of vanadium-benzene sandwich clusters and their anions: V_nBz_n^0/- (n = 1-5) and V_nBz_n1^0/- (n = 2-5)

One end open V_nBz_n^- (n = 1-5; Bz = benzene) and both ends open V_nBz_n-1^- (n = 2-5) vanadium-benzene cluster anions were studied using anion photoelectron spectroscopy and density functional calculations. The smaller (n ≤ 3) V_nBz_n and V_nBz_n-1 clusters and corresponding anions were found to have structural isomers, whereas full-sandwiched V_nBz_n+1 clusters preferred to form multiple-decker sandwich structures. Several isomeric V₂Bz₂ structures were identified theoretically and the anion photoelectron spectra of V₂Bz₂^0/- were explained well by the coexistence of two isomeric structures: (1) a V₂-core structure sandwiched between benzene molecules and (2) an alternating sandwich structure with the spin state strongly dependent on the structure. The adiabatic electron affinity of both V_nBz_n and V_nBz_n-1 was found to increase with the cluster size at larger sizes (n = 4 or 5) and approaches to that of V_nBz_n+1. The evolution of the structural and electronic properties of V_nBz_m and V_nBz_m^- (m = n and n - 1) with size is discussed in comparison with V_nBz_n+1 and V_nBz_n+1^-.