RESUMEN
Cerium oxide cluster cations were reacted with nitric oxide molecules and then measured by ion mobility mass spectrometry (IMMS). CenO2n+1N+ species appeared as products of the reaction CenO2n+ + NO â CenO2n+1N+, and their collision cross sections (CCSs) with helium were obtained by IMMS. The experimental CCSs of CenO2n+1N+ were 2-6 Å2 larger than those of CenO2n+ for n = 4-10. Geometrical structures of Ce4O9N+ and Ce5O11N+ were assigned by comparing experimental CCSs with theoretically calculated CCSs of candidate structures. The suggested structures showed that the adsorbed NO molecule is oxidized by the CenO2n+ cluster into a nitrite (NO2-) or nitrate (NO3-). The CenO2n+1N+ species are regarded as intermediates of the NO oxidation reaction CenO2n+ + NO â CenO2n-1+ + NO2, and therefore, the present results are helpful for understanding redox reactions involving gas-phase CenO2n+ cluster ions.
RESUMEN
Geometric structures of free iridium cluster anions, Irn-, were examined by means of ion mobility mass spectrometry and density functional theory calculation for n = 3-15 with the additional help of photoelectron spectroscopy for n = 4-10. It has been revealed that Irn- clusters with n ≥ 5 favor a square facet and take a cubic motif in contrast to the face-centered cubic structures in the corresponding nanoparticles and bulk. A growth sequence of Irn- for n = 5-15 is proposed: single Ir atoms are sequentially attached to one side of the square plane of Ir4- to form a cubic Ir8-, and are then continuously attached on one of the square facets of Ir8- for n = 9-12 and Ir12- for n = 13-15.
RESUMEN
Stable compositions and structures of copper oxide cluster cations have been studied by ion mobility mass spectrometry (IMMS) and density functional theory calculations. Cluster ions of the series Cu n O m + were predominantly observed with n:m ≈ 2:1 in the mass spectrum. Collision cross sections (CCSs) of the cluster ions with n:m ≈ 2:1, determined by IMMS, were found to increase monotonically with cluster size. In addition, the CCSs of Cu n O n + and Cu n O n-1 + (n = 2-8) were examined, and stepwise increases were observed for Cu n O n-1 + series. These cluster structures were assigned by comparison of the CCSs obtained via the IMMS experiment with theoretical orientation-averaged CCSs of optimized structures.
RESUMEN
Herein, the compositions and geometrical structures of niobium oxide cluster ions were studied and compared with those of the lighter Group 5 counterpart vanadium oxide cluster ions by ion-mobility mass spectrometry (IM-MS). As a result of collision-induced dissociation in IM-MS, the compositions were found to be dependent on an odd and even number of niobium atoms, whereby the ions with (NbO2)(Nb2O5)(m-1)/2+ and (NbO3)(Nb2O5)(m-1)/2- were identified as stable compositions for an odd number of Nb atoms, whereas (Nb2O5)m/2± and (Nb2O6)(Nb2O5)(m-2)/2- were identified as stable compositions for an even number of Nb atom clusters. Furthermore, structural transitions were observed between m = 8 and 9 for cluster cations and m = 7 and 8 for cluster anions for experimental collision cross-sections (CCSs), which were determined from the arrival times in the ion-mobility measurements. Quantum chemical calculations were conducted on several structural candidates of these compositions for m = 2-12. For cluster cations with the sizes between m = 2 and 8 and cluster anions with m = 2-7, the structures were found to be similar to those of vanadium oxide cluster ions upon comparing the experimental CCSs with the theoretical CCSs of optimized structures. As compared to the vanadium oxide cluster ions, niobium oxide cluster cations with m ≥ 9 and anions with m ≥ 8 consisted of structures where some niobium atoms had more than five oxygen-atom coordination; thus, compact structures could be achieved in the case of niobium oxide cluster ions.
RESUMEN
Stable compositions and geometrical structures of vanadium oxide cluster ions, VmOn(±), were investigated by ion mobility mass spectrometry (IM-MS). The most stable compositions of vanadium oxide cluster cations were (V2O4)(V2O5)(m-2)/2(+) and (VO2)(V2O5)(m-1)/2(+), depending on the clusters with even and odd numbers of vanadium atoms. Compositions one-oxygen richer than the cations, such as (V2O5)m/2(-) and (VO3)(V2O5)(m-1)/2(-), were predominantly observed for cluster anions. Assignments of these stable cluster ion compositions, which were determined as a result of collision-induced dissociations in IM-MS, can partly be explained with consideration of spin density distribution. By comparing the experimental collision cross sections (CCSs) obtained from ion mobility measurement with CCSs of the theoretically calculated structures, we confirmed the patterned growth of geometrical structures partially discussed in previous theoretical and spectroscopic studies. We showed that even sized (V2O5)m/2(±) where m = 6-12 had right polygonal prism structures except for the anionic V12O30(-), and for the clusters of odd numbers of vanadium m, cations and anions can either have bridged or pyramid structures. Both of the odd sized structures proposed were derivatives from the even sized right polygonal prism structures. The exception, V12O30(-), which had a CCS almost equal to that of the neighboring smaller V11O28(-), should have a structure of higher density than the right hexagonal prism, in which it was proposed to be a captured pyramid structure, derived from V11O28(-).
