Photoelectron spectroscopic and computational studies of the Pt@Pb101- and Pt@Pb121-/2- anions

Abstract

A combination of anion photoelectron spectroscopy and density functional theory calculations has elucidated the geometric and electronic structure of gas-phase endohedral Pt/Pb cage cluster anions. The anions, Pt@Pb 10 1− and Pt@Pb 12 1− were prepared from "preassembled" clusters generated from crystalline samples of ½Kð2,2,2-cryptÞ 2 ½Pt@Pb 12 that were brought into the gas phase using a unique infrared desorption/photoemission anion source. The use of crystalline ½Kð2,2,2-cryptÞ 2 ½Pt@Pb 12 also provided access to K½Pt@Pb n − anions in the gas phase (i.e., the K þ salts of the Pt@Pb n 2− anions endohedral complex is the only bare cluster that has been structurally characterized in the solid state, solution, and the gas phase.endohedral clusters | negative ions | mass spectrometry T he synthesis, characterization, and solution chemistry of the soluble main group polyanions (i.e., Zintl ions) have a 120-y history (1) that has been well reviewed (2-7). The use of soluble Zintl clusters for the preparation of unique materials was pioneered by Haushalter and O'Connor in the 1980s in their work on magnetic spin glasses, electronic materials, and metallic coatings (8-13). Since that time, scientists have pursued new materials utilizing various Zintl ion precursors to both ionically and covalently link the cluster anions into oligomers (14-18), polymers (19,20), network solids (21-23), and nanomaterials (24-26). Simultaneously, gas-phase chemists have prepared bare (e.g., ligand-free) clusters in molecular beams, studied their size-dependent properties, and explored possible condensed-phased manifestations (27-30). Especially notable was the discovery of C 60 (31) in molecular beam experiments and its subsequent macroscopic synthesis (32). Several other cluster species (not yet assembled into solids) show unusual gas-phase stability (e.g., metcar cages Ti 8 C 12 and Zr 8 C 12 , refs. 33 and 34, and Al 13 1− -type cluster anions comprising icosahedral cages of group 13 elements with one atom inside; i.e., Al@Al 12 1− , refs. 27, 35, and 36). Traditional inorganic cluster compounds are stabilized by ligand spheres that reduce cluster-core interactions. By contrast, bare gas-phase clusters devoid of ligands are vulnerable to coalescence. Combining the attributes of both are salts composed of Zintl cluster anions and their countercations. Not only are Zintl cluster anions ligand free with several structural similarities to gas-phase clusters (e.g., Pt@Pb 12 2− is isostructural to Al 13 1− and the As 20 shell of As@Ni 12 @As 20 3− is isostructural to Ti 8 C 12 and C 20 ), but they can also be prepared in macroscopic quantities, fully characterized, and used in subsequent reactions. Several researchers (3,14,(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48) have prepared and isolated a number of salts of endohedral Zintl anion clusters with unprecedented structures and unique properties; e.g., σ-aromaticity, paramagnetism, and remarkable dynamic exchange processes. These "intermetalloid" clusters (3, 5, 48-51) display struct...

Photoelectron velocity-map imaging signature of structural evolution of silver-doped lead Zintl anions

“…Most of this work has involved the heavy Group 14 element species with the magic cluster size number of 10 and 12. [10][11][12][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45] The Co@Ge 10 3− and Fe@Ge 10 3− clusters 30,31 feature an encapsulated pentagonal prismatic structure (D 5h ), whereas the isoelectronic Ni@Pb 10 2− cluster 28,29 prefers the encapsulated bicapped square antiprism structure (D 4d ). Gas phase experiments show that the stannaspherene (Sn 12 2− ) and plumbaspherene (Pb 12 2− ) cages can trap the main-group and transition metals or the f-block elements except of potassium.…”

Direct experimental observation of weakly-bound character of the attached electron in europium anion

“…We explored this question by utilizing the photoelectron spectroscopy, which has been proven to be a powerful approach to directly probe the electronic properties of atoms and clusters2728293031323334353637383940. Herein, we present direct experimental observations on the features of the electron-atom interaction in Eu − .…”

Mass spectrometry and its role in advancing cluster science

“…Here cationic clusters Bi x Na y + l + , corresponding to Bi x yÀ , appear as magic numbers in the distribution for every reported anionic Zintl ion of bismuth. From the observation of Bi 3 Na 4 + as a magic number in the mass spectrum in within the cluster anions (Na 3 Sn 4 ) À , (NaGa 4 ) À , (KSn 12 ) À , and (KPb 12 ) À , respectively, as well as endohedral [M@Pb 12 ] 2À and [M@Sn 12 ] 2À where M is a transition metal atom have been studied through a combination of anion photoelectron spectroscopy and theorertical calculations [84][85][86][87][88][89][90]. Recently, aluminum moieties within selected Na-Al clusters have been shown to exhibit Zintl characteristics [90].…”