dahl

Research in our group continues to focus mainly on high-nuclearity homometallic and heterometallic carbonyl clusters: namely, those with at least 10 metal-core atoms containing primarily Group 10 (Ni, Pd, Pt) and Group 11 (Cu, Ag, Au) metals that form direct metal-metal bonds. It combines the art of synthesis (involving Schlenkware, preparative vac-line, and drybox techniques) with structural/bonding analyses and physical/chemical charaterization studies. Modern physical methods utilized include CCD X-ray diffraction, spectroscopic (IR, UV-Vis near IR, multinuclear NMR, ESR), mass spectrometric, magnetic susceptibility, and electrochemical measurements.

Because most of these giant-sized metal clusters possess well-defined stoichiometries and precise geometries, detailed investigations of their physical behaviors should produce insight into the onset of metallic-like character with increasing metal-core size (especially for clusters with interior atoms within their metal cores). It will be important to correlate their physical properties (e.g., variable-temperature magnetic moments and specific heats) with those of naked and ligand-stabilized nanoparticles with non-uniform size distributions. These clusters are possible precursors of new materials with useful catalytic, electronic, magnetic, optical and/or photochemical/electrochemical properties.

Recent work has given rise to a considerable number of remarkable new nanosized clusters such as: 1) three isostructural 38-atom trimetallic Au-M-Ni(M=Pd, Pt) and bimetallic Au-Ni carbonyl clusters of pseudo-D3d symmetry with substitutional Pd/Ni crystal-disorder occurring at only six equivalent metal sties (coloring problem), 2) two crystallographically superimposed Au-Ni carbonyl clusters of pseudo-D4d symmetry containing the same 26-atom gold cage (with either one or two interior Au prisoners) surrounded by 40 Ni atoms that are ligated by 56 COs, and 3) a three-shell palladium carbonyl phosphine cluster of pseudo-icosahedral symmetry containing 55 interior Pd atoms in the first two shells encapsulated by a 60-vertex 3rd shell polyhedron ( a geometrical metalloisomer of C60 buckyball) with 30 additional capping Pd atoms.

The diversity of research, in which coworkers are encouraged to develop and broaden their own research projects and to carry out 'operational tests' of their hypotheses in the laboratory, generates a highly stimulating environment with extensive cross-fertilization of ideas and much give-and-take interaction occurring between group members. The following publications illustrate some of our research.