Cluster chirality

Complex clusters incorporating multiple-bridging groups such as O2-, CC1, and CC02 have been known for some time, with clear synthetic routes available.86 Typical species include 03-CCl)Co3(CO)9, (//3-CC02)Co3(CO)9, and Co4(/x4-0)[(/i3-CC02)Co3(CO)9]6. Substitution of further carbonyls can lead to chiral clusters. 

Charge density-NMR chemical shift correlation in organic ions, 11, 125 Charge distribution and charge separation in radical rearrangement reactions, 38, 111 Chemically induced dynamic nuclear spin polarization and its applications, 10, 53 Chemiluminesance of organic compounds, 18, 187 Chiral clusters in the gas phase, 39, 147... 

This volume seeks in a small way to bridge the wide gap between organic chemistry in the gas and condensed phases. The same types of chiral ion-dipole complexes that form as intermediates of solvolysis may be generated in the gas phase by allowing neutral molecules to cluster with chiral cations. The reactions of these chiral clusters have been characterized in exquisite detail by mass spectrometry. The results of this work are summarized by Maurizio Speranza in a chapter that is notable for its breadth and thoroughness of coverage. This presentation leaves the distinct impression that further breakthroughs on the problems discussed await us in the near future. 

Noncovalent interactions in supramolecular systems 152 Noncovalent interactions in life sciences 152 Metal ions in biological systems 153 Chiral clusters 154... 

The state-of-art of the generation, characterization, and evolution of ionic and molecular chiral clusters in the gas phase is illustrated in the present chapter. 

An introduction to the non-covalent forces operating in stable ionic and molecular aggregates will be presented in Section 2. A brief description of the experimental methodologies employed in the production, detection, and characterization of clusters will be given in Section 3. The available experimental evidence on the structure of chiral clusters and their intrinsic stability, reactivity, and evolution dynamics will be presented and discussed in Sections 4 (molecular clusters) and 5 (ionic clusters). In the same sections, the experimental data will be interpreted in the light of the available theoretical evidence. Finally, some concluding remarks will be expressed in Section 6. 

In principle, mass spectrometry is not suitable to differentiate enantiomers. However, mass spectrometry is able to distinguish between diastereomers and has been applied to stereochemical problems in different areas of chemistry. In the field of chiral cluster chemistry, mass spectrometry, sometimes in combination with chiral chromatography, has been extensively applied to studies of proton- and metal-bound clusters, self-recognition processes, cyclodextrin and crown ethers inclusion complexes, carbohydrate complexes, and others. Several excellent reviews on this topic are nowadays available. A survey of the most relevant examples will be given in this section. Most of the studies was based on ion abundance analysis, often coupled with MIKE and CID ion fragmentation on MS " and FT-ICR mass spectrometric instruments, using Cl, MALDI, FAB, and ESI, and atmospheric pressure ionization (API) methods. 

---