Fragmentation pathways of dianionic [Pt2(μ-P2O5H2)4 + X,Y]2− (X,Y = H, K, Ag) species in an ion trap induced by collisions and UV photoexcitation

• First gas phase study of dianionic species [Pt2(μ-P2O5H2)4 + X,Y]2− (X,Y = H, K, Ag).
• Drastic differences between CID and UV-PID fragmentation pathways.
• Photo-induced Ag0 formation via intramolecular electron-transfer.
• PID spectra recorded in the range of 250–400 nm.
• Structural assignments based on DFT/TD-DFT calculations and gas phase data.

We report on the first gas phase study of dianionic species [Pt2(μ-P2O5H2)4 + X,Y]2− (X,Y = H, K, Ag) derived by counterion attachment to the dimetallic [Pt2(μ-P2O5H2)4]4− complex (abbrev. Ptpop). The combined electrospray ionization mass spectrometry and laser spectroscopy investigation provides intrinsic properties and fragmentation pathways without solvent interaction in comparison to calculations by density functional theory (DFT) methods. Drastic differences between collision induced (loss of water) and UV photo-induced fragmentation (electron photodetachment or loss of Ag0) in a quadrupole ion trap are observed. The underlying fragmentation pathways are explored in detail by MSn. Upon UV photoexcitation [Ptpop + H,Ag]2− and [Ptpop + 2Ag]2− exhibit dissociation of Ag0 indicating an intramolecular electron transfer, whereas mainly electron photodetachment is observed for [Ptpop + 2H]2− and [Ptpop + H,K]2−. Channel specific photo-induced dissociation spectra in the range of 250–400 nm reveal the main band at ∼370 nm in remarkable resemblance to aqueous absorption spectra. Additional absorption features, distinct broadening and spectroscopic shifts depending on counterions and fragment channels are also observed. For the ground state structures a side-on coordination of metal counterions to the [Pt2(μ-P2O5H2)4]4− framework is deduced based on fragmentation pathways, results of geometry optimizations and calculated absorption spectra.

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