Vanadium atomic properties

Valence, 286 Valence electrons, 269 and ionization energies, 269 Vanadium atomic radius, 399 eleciron configuration, 389 oxidation numbers, 391 pentoxide catalyst, 227 properties, 400, 401 van der Waals forces, 301 elements that form molecular crystals using, 301 and molecular shape, 307 and molecular size, 307 and molecular substances, 306 and number of electrons, 306 van der Waals radius, 354 halogens, 354 Vanillin, 345... 

Vanadium atom depositions were further studied in alkane matrices 109) in an effort to observe the influence of other low-temperature, matrix environments on the optical spectra and clustering properties of metal atoms. Thus, vanadium atoms were deposited with a series of normal, branched, and cyclic alkanes over a wide range of temperature. The atomic spectra were somewhat broadened compared to those in argon, but the matrix-induced, frequency shifts from gas-phase values were smaller. As shown in Fig. 3, these shifts decrease with in-... 

The electronic and magnetic properties of vanadium tetramethoxide are consistent with a trimeric structure involving six-coordinate vanadium atoms, while the electronic spectrum of deep blue V(OBu )4 is consistent with a slightly distorted monomeric, tetrahedral structure.181... 

Interest in the interpretation of the spectral and magnetic properties of oxo-vanadium(iv) complexes has grown as it has become apparent that the general assumption of overall C4 symmetry for these complexes is unjustified. Bis-(2-methyl-8-quinolato)oxovanadium(iv), VO(quin)2,395 and bis(tetramethylurea)dichloro-oxo-vanadium(iv), VO(tmu)2Cl2,396 for example, have been found to be five-co-ordinate with a trigonal-bipyramidal co-ordination polyhedron about the vanadium atom. A crystal-field model has been developed which gives a good account of the electronic and e.p.r. spectra of VO(quin)2. 

The 0 + (vanadyl) ion is one of the most stable oxo-metal species known, and probably the most stable diatomic ion. Most of these properties stem from the ground-state electronic configuration of the vanadium atom, [Ar]3d, which shows similarities to the Cu + d system. The ion also lends itself to study by ESR because of the isotopic purity of the V isotope, its high nuclear spin, / = 7/2, and the single unpaired outer electron. 

The similar structural and catalytic properties of the SiOj-supported and unsupported samples prepared from the same precursor suggest that the same active surface is formed on both types of samples. The higher conversions obtained with the supported samples could be attributed to higher dispersions of the VPO compounds. The slightly lower maleic anhydride selectivity observed for catalyst A than B or the bulk catalyst could be due to some phosphorus atoms interacting with the silica surface rather than with vanadium atoms, such that the P/V ratio is less than two in the VPO compounds. Addition of phosphorus to catalyst B replenished this lost phosphorus. Previous studies of supported vanadium-phosphorus oxides have shown that some phosphorus atoms can be associated with the silica [2,8]. The catalytic properties of the supported samples as well as the LRS are similar to the SiOj-supported PA =2 VPO samples prepared previously [2,3]. These earlier samples were prepared by adding H3PO4 to PA =1 samples synthesized by various synthesis routes. Thus, for the supported samples, the method of preparation is much less important than the composition. 

Radicals having rather similar properties (Table X) containing one vanadium atom are formed on exposure of molybdates doped with vanadate to y-rays (41). We have also prepared radicals which could well be Nb042" and M0O4". 

The physico-chemical properties of the supports and vanadium oxide catalysts are listed in Table 2. The catalysts are labeled XVj/M, where X corresponds to the % by weight of vanadium, V to vanadium, p to the preparation method (imp=impregnation, graf=grafting) and M to the support. No marked effect of the deposition of titanium oxide on the specific surface area of the silica was detected in the case of the support TSm, while, in the case of the vanadium-based catalysts, a decrease in Sbet was observed. The vanadium surface densities are calculated as number of vanadium atoms per square nanometer of catalyst (V/nm oat) to facilitate a comparison of the samples prepared on different surface area supports [6]. The vanadium contents of the samples are quite smaller than the theoretical monovanadate monolayer coverage of 2.3 VO,/nm" [6]. 

Association with 7T-systems The influence of donor-acceptor properties of a large aromatic 7T-system exerted on the vanadium system will change the vertical distance of vanadium atoms to the approximate ligand plane of the heterocyclic atoms (Figure 10.3). 

Salts of hexafluorovanadate can be obtained by high temperature techniques or from solutions containing hydrofluoric acid. For instance. X-ray patterns and DTA were used for the characterization of 17 double fluorides obtained by solid state reactions in the systems VF3 -I- MF (M = Li, Na, K, Rb, Cs, Tl) and seven double fluorides in the systems VF3 -I- MF2 (M = Ca, Sr, Ba, Pb), and the lattice constants - and magnetic properties of A2B[VF6] (A, B = Cs, Rb, Tl, K, Na, Li) were also reported. The structure of the high temperature p phase of LisVFe has been determined and compared with the cryolite-type stable a form. The vanadium atoms have an octahedral coordination. ... 

Fig. 8 Representation of the molecular structure of the V15 complex (left). The larger spheres correspond to the vanadium atoms. Scheme showing the interactions between the V(IV) cations corresponding to the six exchange interactions considered for the description of the magnetic properties (right)...

Our DPT investigations show that the penta-coordinated vanadium atoms show a unique influence on the structural properties of the glasses. 

Vanado-phosphate glasses (VPGs) are well known for their semi-conductive behaviour [72]. In the last decades they were widely studied in order to understand the mechanism underneath their electronic properties. The electronic conductivity was correlated to small polaron hopping between vanadium ions with different valence state [86], favoured by their electronic configuration [87]. In VPGs, vanadium atoms are mainly characterized by two oxidation states, 4+ and 5+, and the and based interconnected polyhedra become the preferential path for the polaron hopping [88]. Therefore, the relative amount of these two species (V" + and V +), which is usually expressed as V" +A tot ratio, influences the final electrical properties of VP systems [86, 89]. 

Pati and coworkers modeled nanojunctions consisting of three pairs of vanadium atoms bonded to the first and third hexagons of two anthracene and its isoelectronic BN-analog and coupled to two graphene layers on either sides of V2-antracene-V2-antracene-V2 complex [152]. The system possessed spin filter properties and was suggested as a possible spin filter in spintronic devices. 

Under similar reaction-conditions, the vanadium species V(N2)6 (139) has been isolated. In addition, a species V2(Na) (n probably = 12) was observed (139). The metal nuclearity was established by the standard, metal-concentration techniques. A comparison of the optical spectra of V(N2) and V(CO)e 128) suggested that these molecules have very similar, electronic properties, and the data clearly established that N2 is a strong, field ligand in its bonding properties. Interestingly, atomic V could be isolated in N2 matrices from 8- 12K co-... 

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