Chemistry and Biochemstry Department Seminar: Dr. Lai-Sheng Wang of Brown University
|Category:||College Of Arts And Sciences|
|Date & Time:||
from 04:00 PM to 05:30 PM
|Sponsored by:||Chemistry & Biochemistry Deptartment|
TITLE: "Nanocluster of Boron and Gold"
Clusters are aggregates of atoms, which exhibit size-dependent chemical and physical properties. In my lab, photoelectron spectroscopy is used to probe the size-dependent structures and electronic properties of a variety of clusters in the size range from a few atoms to hundreds of atoms. In this talk, I will present our studies on gold and boron clusters. Even though bulk gold is the most inert metal, gold nanoparticles less than 5 nm in diameter are found to have remarkable catalytic activities. This finding has stimulated a flurry of studies about the structures and chemical reactivities of well-defined and isolated gold clusters. We have elucidated the structures of size-selected gold clusters with more than 60 atoms and found interesting size-dependent structural variations and chemical reactiviteis [1-3], which provide insight into the catalytic mechanisms of gold nanoparticles.
In our study of boron clusters, we found that they all possess planar or quasi-planar structures , in contrast to bulk boron, which is dominated by three-dimensional cage-like building blocks. The propensity for planarity has been found to be due to both σ and π electron delocalization throughout the molecular plane, giving rise to concepts of σ and π multiple aromaticity. Our very recent work has shown that the central boron atoms can be substituted by transition metal atoms to form a new class of aromatic boron compounds, which consist of a central metal atom and a monocyclic boron ring (M©Bn). Eight-, nine-, and ten-membered rings of boron have been observed, giving rise to a family of novel borometallic compounds [5,6].