Compositions and structures of niobium oxide cluster ions, Nb_mO_n^±, (m = 2–12), revealed by ion mobility mass spectrometry

Abstract

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 (NbO)(NbO) and (NbO)(NbO) were identified as stable compositions for an odd number of Nb atoms, whereas (NbO) and (NbO)(NbO) 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.

Structures of stoichiometric sodium oxide cluster cations studied by ion mobility mass spectrometry

“…Accordingly, the arrival time of NaO(Na 2 O) (n−1)/2 + tends to be longer than those of Na(Na 2 O) (n−1)/2 + with the same n. This general relationship sometimes does not hold due to a large structural difference. Gradual broadening of the peak widths was also observed with increasing n. As a result of analysis based on gasdiffusion theory, this broadening was mainly due to the diffusion of ion packets before injection to the ion drift cell as discussed in our previous work [31].…”

Stable Compositions and Structures of Copper Oxide Cluster Cations CunOm+ (n = 2–8) Studied by Ion Mobility Mass Spectrometry

“…The E / N conditions were kept at 23 Td in the present measurement by setting buffer-gas pressure and temperature in the ion-drift cell at 0.80 Torr and 180 K, respectively. Under these conditions, the effective temperature of the Cu 4 O 2 + ion, for example, was estimated to be about 240 K. These conditions have already been confirmed as reliable to measure precise CCSs of ions by the author’s group …”

“…Under these conditions, the effective temperature of the Cu 4 O 2 + ion, for example, was estimated to be about 240 K. These conditions have already been confirmed as reliable to measure precise CCSs of ions by the author’s group. 38…”

“…Under these conditions, the effective temperature of the Cu 4 O 2 + ion, for example, was estimated to be about 240 K. These conditions have already been confirmed as reliable to measure precise CCSs of ions by the author's group. 38 3. COMPUTATIONAL METHODS Density functional theory calculations for optimization of the structures of copper oxide cluster ions, Cu n O m + , were performed prior to the calculations of the CCSs of the cluster ions.…”

Collision cross sections of negative cluster ions of phosphoric acid in N2 determined by drift tube ion mobility and their use in travelling wave ion mobility

“…13,14,15 Cluster ions are readily produced using direct infusion of salt solutions with an electrospray ion source and are routinely used for calibration of mass analyzers. 16,17,18,19,20 A number of ionic clusters derived from alkali halides salts, 21,22,23 ionic liquids 24,25,26,27 and transition metal oxides 28,29,30,31,32,33 have been studied by drift tube ion mobility mainly and differential mobility analysis-time-of-flight mass spectrometry. Since a first study in 2014, 34 we have started studying negative phosphoric acid cluster ions in view of investigating their potential as reference for the calibration of the TWIMS.…”