We present a study of the structural evolution of palladium cluster anions in a size range from 55 to 147 atoms using a combination of trapped ion electron diffraction and density functional theory computations. We show that Pdn- clusters (n = 55, 65, 75, 85, 95, 105, and 147) change from an icosahedral motif at Pd55- to the bulk fcc motif at Pd147-. This size-dependent structure transition is probed experimentally at a temperature of 95 K and characterized by a continuously increasing fraction of fcc isomers over the considered size range showing a crossover to the fcc motif at n ≈ 90.

Homonuclear 55-atom …︁ …︁ transition-metal clusters of the 3d and 4d elements show a correlation between the cluster structure type (atomic symbol, bottom right corner) and the bulk lattice morphology (top left corner). This link is found by gas-phase electron diffraction and DFT calculations. In their Communication on page 6102 ff., D. Schooss et al. also describe how the cluster structure types differ in maximum atomic coordination numbers in analogy to the coordination numbers in the bulk lattices.

Homonukleare 55-atomige Übergangsmetallcluster …︁ …︁ der 3d- und 4d-Elemente weisen eine Korrelation zwischen dem Cluster-Strukturtyp (rechte untere Ecke des Atomsymbols) und der Festkörperstruktur (linke obere Ecke) auf. Dies ergaben Gasphasen-Elektronenbeugung und DFT-Rechnungen. D. Schooss et al. beschreiben in der Zuschrift auf S. 6218 ff. außerdem, dass die Cluster-Strukturtypen sich analog zu den Koordinationszahlen im Festkörper in den maximalen atomaren Koordinationszahlen unterscheiden.

Korrelation von Cluster- und Festkörperstruktur: Elektronenbeugungsexperimente an einer Reihe homonuklearer 55-atomiger Clusteranionen der 3d- und 4d-Übergangsmetalle zeigen lediglich vier unterschiedliche Strukturfamilien. Elemente gleicher Festkörperstruktur weisen einen gemeinsamen Clusterstrukturtyp auf. Die Clusterstrukturtypen unterscheiden sich durch die maximale Koordinationszahl in Analogie zu den entsprechenden Festkörperstrukturen.

Correlation of cluster and bulk structure: Electron-diffraction measurements of homonuclear 55-atom transition-metal cluster anions covering essentially all 3d and 4d elements show only four main structure families. Elements with the same bulk lattice morphology generally have a common cluster structure type. The cluster structure types differ in maximum atomic coordination numbers in analogy to the coordination numbers in the corresponding bulk lattices.

The structures of bismuth cluster cations in the range between 4 and 14 atoms have been assigned by a combination of gas phase ion mobility and trapped ion electron diffraction measurements together with density functional theory calculations. We find that above 8 atoms the clusters adopt prolate structures with coordination numbers between 3 and 4 and highly directional bonds. These open structures are more like those seen for clusters of semiconducting-in-bulk elements (such as silicon) rather than resembling the compact structures typical for clusters of metallic-in-bulk elements. An accurate description of bismuth clusters at the level of density functional theory, in particular of fragmentation pathways and dissociation energetics, requires taking spin-orbit coupling into account. For n = 11 we infer that low energy isomers can have fragmentation thresholds comparable to their structural interconversion barriers. This gives rise to experimental isomer distributions which are dependent on formation and annealing histories.

The structures of medium sized tin cluster anions Sn(n)(-) (n = 16-29) were determined by a combination of density functional theory, trapped ion electron diffraction and collision induced dissociation (CID). Mostly prolate structures were found with a structural motif based on only three repeatedly appearing subunit clusters, the Sn(7) pentagonal bipyramid, the Sn(9) tricapped trigonal prism and the Sn(10) bicapped tetragonal antiprism. Sn(16)(-) and Sn(17)(-) are composed of two face connected subunits. In Sn(18)(-)-Sn(20)(-) the subunits form cluster dimers. For Sn(21)(-)-Sn(23)(-) additional tin atoms are inserted between the building blocks. Sn(24)(-) and Sn(25)(-) are composed of a Sn(9) or Sn(10) connected to a Sn(15) subunit, which closely resembles the ground state of Sn(15)(-). Finally, in the larger clusters Sn(26)(-)-Sn(29)(-) additional bridging atoms again connect the building blocks. The CID experiments reveal fission as the main fragmentation channel for all investigated cluster sizes. This rather unexpected "pearl-chain" cluster growth mode is rationalized by the extraordinary stability of the building blocks.

We employ a combination of ion mobility measurements and an unbiased systematic structure search with density functional theory methods to study structure and energetics of gas phase tin cluster cations, Sn(n)(+), in the range of n = 3-15. For Sn(13)(+) we also carry out trapped ion electron diffraction measurements to ascertain the results obtained by the other procedures. The structures for the smaller systems are most easily described by idealized point group symmetries, although they are all Jahn-Teller distorted: D(3h) (trigonal bipyramid), D(4h) (octahedron), D(5h) (pentagonal bipyramid) for n = 5, 6, and 7. For the larger systems we find capped D(5h) for Sn(8)(+) and Sn(9)(+), D(3h) (tricapped trigonal prism) and D(4d) (bicapped squared antiprism) plus adatoms for n = 10, 11, 14, and 15. A centered icosahedron with a peripheral atom removed is the dominant motif in Sn(12)(+). For Sn(13)(+) the calculations predict a family of virtually isoenergetic isomers, an icosahedron and slightly distorted icosahedra, which are about 0.25 eV below two C(1) structures. The experiments indicate the presence of two structures, one from the I(h) family and a prolate C(1) isomer based on fused deltahedral moieties.

In this work the mutual influence of Jahn-Teller (JT) and spin-orbit effects on the photoelectron spectrum of PtCl62- is analyzed. For this purpose potential energy surfaces of PtCl6- along the JT active modes are calculated in the four-component Dirac-Coulomb (DC) framework and the possible JT stabilizations are determined. For the relativistic calculation we set out from the one-particle propagator implemented on the basis of the DC Hamiltonian. A correlated four-component approach is favorable for complexes with a strongly relativistic central atom due to the complicated interplay of electron correlation and relativity. PtCl62- possesses a long enough lifetime which makes it amenable to precise experimental measurements. In the photoelectron spectrum of PtCl62- some peaks could not be unambiguously assigned either originating from a JT splitting or representing individual spin-orbit components. In previously calculated dianionic tetrahalide platinum complexes PtX42- (X=F,Cl,Br) it was observed that spin-orbit effects dominate over the d-orbital-induced JT effects. The same trend also persists in the currently studied hexachlorocomplex where sizable platinum-induced spin-orbit splittings give rise to features that supersede any JT structures.

In this work the mutual influence of Jahn-Teller (JT) and spin-orbit effects on the photoelectron spectrum of PtCl(6)(2-) is analyzed. For this purpose potential energy surfaces of PtCl(6)(-) along the JT active modes are calculated in the four-component Dirac-Coulomb (DC) framework and the possible JT stabilizations are determined. For the relativistic calculation we set out from the one-particle propagator implemented on the basis of the DC Hamiltonian. A correlated four-component approach is favorable for complexes with a strongly relativistic central atom due to the complicated interplay of electron correlation and relativity. PtCl(6)(2-) possesses a long enough lifetime which makes it amenable to precise experimental measurements. In the photoelectron spectrum of PtCl(6)(2-) some peaks could not be unambiguously assigned either originating from a JT splitting or representing individual spin-orbit components. In previously calculated dianionic tetrahalide platinum complexes PtX(4)(2-) (X = F,Cl,Br) it was observed that spin-orbit effects dominate over the d-orbital-induced JT effects. The same trend also persists in the currently studied hexachlorocomplex where sizable platinum-induced spin-orbit splittings give rise to features that supersede any JT structures.

In this work we calculate the photoelectron spectra of the PtX(4) (2-) (X=F,Cl,Br) dianions by application of the third-order Dirac-Hartree-Fock one-particle propagator technique. Relativistic effects and electron correlation are hereby treated on a consistent theoretical basis, which is mandatory for systems containing heavy elements. An experimental PtF(4) (2-) gas phase photoelectron (PE) spectrum is not available and our calculations confirm its instability against autodetachment. For PtCl(4) (2-) potential curves for the two Jahn-Teller (JT), active modes were determined and the influence of spin-orbit splitting on the JT stabilization is discussed. The scalar relativistic and four-component potential energy curves hereby exhibit remarkable differences relevant for the correct interpretation of the spectra. A dissociation channel through the b(2g) vibrational mode was obtained for PtCl(4) (2-) in the (2)E(u) final state. For all species electron correlation strongly decreases the ionization potentials and the inclusion of spin-orbit coupling leads to alterations in the level order, which have to be taken into account for a correct peak assignment. The metal d contribution to the valence orbitals steadily decreases from the PtF(4) (2-) to the PtBr(4) (2-) compound, which rules out a pure metal d-orbital-based interpretation of the valence PE spectrum.