Properties that vary with particle size are an important feature of nanoscale materials. CdSe quantum dot nanocrystals vary in color from green–yellow to orange–red and luminesce from blue to yellow, where shorter wavelength, higher energy, electronic transitions correspond to smaller particle sizes. CdSe quantum dot nanocrystals are a visually engaging way to demonstrate quantum effects in chemistry, since their transition energies can be explained as a "particle in a box", where a delocalized electron is the particle and the nanocrystal is the box. Following the method pioneered by Xiaogang Peng and coworkers, CdSe nanocrystals are synthesized from CdO, oleic acid, elemental Se, and trioctylphosphine using a kinetic growth method in octadecene at 225 °C and a less than three-minute reaction time. This synthesis has several advantages over methods using dimethyl cadmium, a chemical that is extremely toxic, expensive, unstable, pyrophoric, and requires inert atmosphere techniques. When excited at 400 nm, the colloidal suspensions of quantum dots give relatively sharp emission spectra with ∼35-nm peak widths, indicating monodisperse particle sizes. Corresponding absorbance spectra are also of high quality.

A populous group of ternary trielide rich (Al, Ga, In) intermetallics forming the NaZn(13) structure type has been synthesized from stoichiometric combinations of the elements in an arc melter. These ternary compounds have the general formula AM(x)()T(13)(-)(x)(), where A = Ba, Sr, La, Eu, M = Cu and Ag, and T = Al, Ga, and In, with 5

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press. I81 Due to the strongly elongated bonds thecompounds modeled here are the first examples of cobalt(ti1) hexaamines for which an anharmonic potential is required, and for which this may be accurately parameterized. The quality of the parameters is based on structural data, including that of the yellow isomer and a set of cobalt(rn) amines with moderately long bonds, and on the computed ligand field and redox properties (see below and ref. (71). [9] a) P. Ill] CAMMAG [I21 was used for the AOM calculations. 1121 a) M. Gerloch, M . CAMMAG, a Fortran Program for AOM Calculations, University ofcambridge, U. K.; b) H. Stratemeier, M. A. Hitchman, P. Comba, P V. Bernhardt, M. J. Riley, Inorg. Chern. 1991,30,4088; the parameterization is described in ref. [9]. [13] Ligand-induced steric strain is not the only contribution to the redox potentla1 of coodination compounds, and other effects have been discussed in detail [5,7]. The admittedly nmplistic approach used here was shown to lead to valuable results for hexaaminecobalt(m/ri) couplesMain-group intermetallic phases can be classified into three groups based on the valence electron concentration (VEC) per atom: Hume-Rothery phases with VEC<2, Zintl phases with VEC > 4, and compounds with 2 < VEC < 4 whose structures cannot be rationalized by any simple electron-counting rules. Compounds of these three classes display a rich variety o f structures and compositions ranging from close-packed structures with wide phase widths to valence compounds containing covalent two-center, two-electron bonds."' Many of these intermetallic phases offer chemists the challenge of complex structural features such as fractional and mixed site occupancies, site preferences, vacancy ordering, and structural phase transitions.Ostenson for magnetic susceptibility measurements.In addition to careful crystallography, calculations of electronic structure are essential for understanding the structures of these compounds. To explore the connection between VEC and siructure type for the compounds between the Hume-Rothery phases and the Zintl phases, we focused on the synthesis, characterization, and determination o f electronic structure of new ternary aluminum-rich intermetallic phases with 2

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