Ionization Energies and Bonding Scheme of Multiple-Decker Sandwich Clusters:  M_n(C₆H₆)_n+1

Abstract

The preparation of multiple-decker sandwich clusters V n (C6H6) n +1 and their large size dependence of the ionization energies have recently been reported by Kaya and his co-workers (J. Phys. Chem. 1995, 99, 3053). In the present paper, the bonding scheme between benzene and metal atoms (Ti, V, and Cr) was investigated by using Mayer's bond order analysis with ab initio MO calculations, and it was attributed mainly to the delocalization of metal dδ electrons via the LUMOs of the benzene molecules. Moreover, the lowest ionization of most multiple-decker sandwich clusters was found to occur from the upper end of the dδ orbitals, and the large size dependence of the ionization energies was also related to the significant one-dimensional delocalization of these dδ electrons. The proposed Hückel type treatment for these frontier orbitals explains the above properties very simply and suggests also the large size dependence of the photoabsorption band positions and even the thermodynamical stability of the one-dimensional polymer materials denoted by [M(C6H6)]∞. Besides, the ionization energies of these polymeric species are estimated to be 2.68, 3.15, and 4.28 eV for M = Ti, V, and Cr, respectively.

Induced Aromaticity and Electron-Count Rules for Bipyramidal and Sandwich Complexes of s- and d-Metals

“…In accordance with [25] the 30-electron triple-decker analogue of chromocene is expected to have a stable structure 59 (Fig. 14) even more aromatic than the predecessing system 45.…”

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

“…20 This E i tendency has been theoretically explained as the delocalization of d electrons along the molecular axis. 23,67 In this section, the electronic structures of the multipledecker VBz sandwich clusters are discussed by the measurements of PIE curves. The second ionization threshold is found as a second onset in the PIE curve, and the values are compared with theoretical predictions on the quasi-band electronic structure.…”

“…When the theoretical analysis of the E i 's was carried out by applying the simple Hückel method to the one-dimensional BzVBzVÁ Á ÁVBz structure (Bz: benzene), 67 the experimental lowest E i 's for n = 1, 2, and 3 can lead to that the Hückel parameters U and ¢ 2 evaluated are 2.766 eV and 0.9893. Having determined these parameters, all the remaining eigenvalues can be obtained for various cluster size.…”

“…86, No. 4 (2013)of E i is theoretically elucidated 23,67 that the ionization occurs from delocalized molecular orbital of vanadiumvanadium interaction interposed by ³* orbitals of benzene. In [Ln n -(COT) n+1 ], however, an orbital contributing to the ionization process is considered to be discontinuously localized along the molecular axis, because the cluster is bonded through ionic bonds and the charge is localized at each component.…”

“…For gas-phase studies discussed above, some intriguing functional clusters such as multidecker organometallic clusters and metal atom encapsulating silicon caged clusters have been successfully synthesized by combining laser-vaporization techniques with molecular beam methods. 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.…”