Gas-phase VUV photoionisation and photofragmentation of the silver deuteride nanocluster [Ag 10 D 8 L 6 ] 2+ (L = bis(diphenylphosphino)methane). A joint experimental and theoretical study

• Published in: Physical chemistry chemical physics : PCCP 2015, Vol.17 (39), p.25772-25777
• Main Authors: Daly, Steven, Krstić, Marjan, Giuliani, Alexandre, Antoine, Rodolphe, Nahon, Laurent, Zavras, Athanasios, Khairallah, George N., Bonačić-Koutecký, Vlasta, Dugourd, Philippe, O'Hair, Richard A. J.
• Format: Article
• Language: English
• Subjects: Adiabatic flow; Chemical Sciences; Clusters; Deuterides; Ionization; Mathematical analysis; Nanostructure; Photoionization; Photons; Physics
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/C5CP01160D

The bis(diphenylphosphino)methane (L = Ph 2 PCH 2 PPh 2 ) ligated silver deuteride nanocluster dication, [Ag 10 D 8 L 6 ] 2+ , has been synthesised in the condensed phase via the reaction of bis(diphenylphosphino)methane, silver nitrate and sodium borodeuteride in the methanol : chloroform (1 : 1) mixed solvent system. The photoionisation and photofragmentation of this mass-selected cluster were studied using a linear ion trap coupled to the DESIRS VUV beamline of the SOLEIL Synchrotron. At 15.5 eV the main ionic products observed are [Ag 10 D 8 L 5 ] 2+ , [Ag 10 D 8 L 4 ] 2+ , [Ag 10 D 8 L 6 ] 3+ ˙, [Ag 9 D 8 L 4 ] 2+ ˙, and [AgL 2 ] + . The later two products arise from fragmentation of [Ag 10 D 8 L 6 ] 3+ ˙. An analysis of the yields of these product ions as a function of the photon energy reveals the onset for the formation of [AgL 2 ] + and [Ag 9 D 8 L 4 ] 2+ ˙ is around 2 eV higher than that for ionisation to produce [Ag 10 D 8 L 5 ] 3+ ˙. The onset of ionisation energy of [Ag 10 D 8 L 6 ] 2+ was determined to be 9.3 ± 0.3 eV from a fit of the yield of the product ion, [Ag 10 D 8 L 6 ] 3+ ˙, as a function of the VUV photon energy. DFT calculations at the RI-PBE/RECP-def2-SVP level of theory were carried out to search for a possible structure of the cluster and to estimate its vertical and adiabatic ionisation energies. The calculated lowest energy structure of the [Ag 10 D 8 L 6 ] 2+ nanocluster contains a symmetrical bicapped square antiprism as a silver core in which hydrides are located as a mix of triangular faces and edges. Four of the bisphosphines bind to the edges of the cluster core as bidentate ligands, the remaining two bisphosphines bind via a single phosphorus donor atom to each of the apical silver atoms. The DFT calculated adiabatic ionisation energy for this structure is 8.54 eV, in satisfactory agreement with experiment.