Gas-Phase Fragmentation Pathways of Mixed Addenda Keggin Anions: PMo_12-nW_nO₄₀^3– (n = 0–12)

Abstract

Abstract. We report a collision-induced dissociation (CID) investigation of the mixed addenda polyoxometalate (POM) anions, PMo 12-n W n O 40 3-(n = 0-12). The anions were generated in solution using a straightforward single-step synthesis approach and introduced into the gas phase by electrospray ionization (ESI). Distinct differences in fragmentation patterns were observed for the range of mixed addenda POMs examined in this study. CID of molybdenum-rich anions, PMo 12-n W n O 40 3-(n = 0-2),generates an abundant doubly charged fragment containing seven metal atoms (M) and 22 oxygen atoms ( and M 7 O 22 2-fragment ions is different from that predicted by a random distribution, indicating substantial segregation of the addenda metal atoms in the POMs. Charge reduction of the triply charged precursor anion resulting in formation of doubly charged anions is also observed. This is a dominant pathway for mixed POMs having a majority (8-11) of W atoms and a minor channel for other precursors indicating a close competition between fragmentation and charge loss pathways in CID of POM anions.

In Situ Infrared Spectroelectrochemistry for Understanding Structural Transformations of Precisely Defined Ions at Electrochemical Interfaces

“…The WPOM anions examined in this study are structurally more rigid than MoPOM anions . Gas-phase studies also indicate that WPOM anions undergo dissociation at higher internal energies than MoPOM . Thus, changes in different types of W–O bond lengths are expected to be less pronounced in WPOM compared with MoPOM.…”

“…The thin-film solid-state electrochemical cell developed in this study is well-suited for characterizing structural transitions at technologically relevant operating EEIs that are of interest to the development of robust and efficient electrochemical interfaces for functional devices. A combination of ion soft landing with the in situ IR spectroelectrochemical technique offers a unique platform to understand structural transformation during redox processes of mass-selected anions or cations and molecular fragments produced by in-source collision-induced dissociation which are difficult to synthesize and stabilize in solution-phase chemistry. ,, In principle, the platform developed in this work can be coupled with a mass-selected nanoparticle deposition system to study the reactive electrochemistry of precisely selected nanoclusters of specific size, shape, and morphology. ,, These capabilities will open up new opportunities for molecular-level studies of interfacial processes occurring at electrochemical interfaces used in electrocatalysis, energy conversion, and storage.…”

“…27 The ability to accommodate 24 electrons (e − ) with retention of structural integrity was reported previously for PMo 12 O 40 3− , making this and related POM anions promising candidates for use in rechargeable batteries, 28 water electrolyzers, 29 electrocatalysts, 30 and molecular supercapacitors. 31 In this study, we selected tungsten POM (WPOM) anions (PW 12 O 40 3− ) as a model system due to their established structural stability 32 and well-defined IRRAS bands. 33 The stability and rigidity of WPOM makes it resilient toward structural transformations during redox processes.…”

Controlling the Activity and Stability of Electrochemical Interfaces Using Atom-by-Atom Metal Substitution of Redox Species

“…The mixed-addenda Mo x W 12– x ( x = 0, 1, 2, 3, 6, 9, and 12) anions were prepared in a one-pot synthesis using specific molar ratios of salts of PMo 12 O 40 : PW 12 O 40 (1:11, 2:10, 3:9, 1:1, 9:3) as detailed in section 2 of the Supporting Information. , …”

TiO2 Nanocoral Structures as Versatile Substrates for Surface‐Assisted Laser Desorption/Ionization Mass Spectrometry

“…Among these, MS is an important analytical technique for accurately determining the structures and compositions of POMs. Both ESI and MALDI have been used as ionization techniques for POMs for MS analysis. Figure a–b shows negative ion SALDI mass spectra of dodecatungstosilicic acid (H 4 SiW 12 O 40 , SiW12) and phosphomolybdic acid (H 3 PMo 12 O 40 , PMo12), which are typical POMs, obtained by using TNC substrates.…”