Vanadium cluster anions

Iseda M, Nishio T, Han S Y, Yoshida H, Terasaki A and Kondow T 1997 Electronic structure of vanadium cluster anions as studied by photoeieotron spectroscopy J. Chem. Phys. 106 2182... 

In the first place, the photoelectron spectrum of vanadium cluster anions (V 3 < n < 100) is shown in Fig. 8. As the cluster-size increases, the spectral feature changes significantly until the size of 10 and, above it, remains unchanged, but its onset energy gradually increases. The vertical detachment energy of the vanadium cluster anion derived from the onset energy of the photoelectron is plotted as a function of (see... 

Fig. 27. In vanadium borate 106 the macrocyclic borate ring (left) is sandwiched by two smaller (VO)60i2 rings (right) of triangular form via six axial B-( 3-0)-V bonds to form a cage-like cluster anion...

Vanadium borophosphates 107-109 that contain cluster anions with different ring sizes can be synthesized by hydrothermal reactions of vanadium(III) oxide, boric acid and an appropriate phosphate salt [145,146]. The ring size of the cluster anion with the composition [(VO)2BP20iol 4-6 is determined by the size of the cation that is, however, included only in the interior of the cages with n = 5 and 6 (Fig. 28). 

Fig 28. Vanadium borophosphates with the composition [(VO)2BP20io] n form cage-like cluster anions, which may be empty (107, n = 4) or centered by a cation (109, n = 6). For clarity only half of the vanadium and phosphorus atoms of the cluster anions are shown... 

Stein et al. and Janauer et al. have synthesized layered mesostructured materials of (C,9H42N)6(H2W,204o) and [Ci2H25N(CH3)3]6(H2Wi2O40), respectively [2,8]. These materials are of great interest because their walls are made of cluster anions, in contrast to the amorphous walls of the other materials. The tungsten, vanadium, niobium, and molybdenum oxide precursors reacting with cationic surfactants, often form similar cluster ion salts with lamellar structures [2]. 

A more powerful experimental technique to probe the electronic structure of transition-metal clusters is size-selected anion photoelectron spectroscopy (PES) [70. 71. 72. 73. 74. 75 and 76]. In PES experiments, a size-selected anion cluster is photodetached by a fixed wavelength photon and the kinetic energies of the photoemitted electrons are measured. PES experiments provide direct measure of the electron affinity and electronic energy levels of neutral clusters. This technique has been used to study many types of clusters over a large cluster size range and can probe how the electronic structures of transition-metal clusters evolve from molecular to bulk [77. 78. 79, 80 and M] Research has focused on the 3d transition-metal clusters, for which there have also been many theoretical studies [82, M, M, 86, M and 89]. It is found that the electronic structure of the small transition-metal clusters is molecular in nature, with discrete electronic states. However, the electronic structure of the transition-metal clusters approaches that of the bulk rapidly. Figure Cl. 14 shows that the electronic structure of vanadium clusters with 65 atoms is already very similar to that of bulk vanadium [90]. Other 3d transition-metal clusters also show bulk-like electronic structures in similar size range [78]. 

Figure 5 Structure of the cluster anion [H6Vi203oF2] . The vanadium ions are shown as black spheres, the fluoride atoms by the gray spheres. The small white spheres are oxygen atoms and the smaller white spheres...

Zemski KA, Justes DR, Bell RC, Castleman AW Jr (2001) Reactions of niobium and tantalum oxide cluster cations and anions with n-butane. J Phys Chem A 105 4410 Bell RC, Castleman AW Jr (2002) Reactions of vanadium oxide cluster ions with 1, 3-butadiene and isomers of butane. J Phys Chem A 106 9893... 

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