Chapter Vi. Analysis of High Molecular Mass Inorganic Complexes Using Matrix-assisted- Laser Desorption/ionization (maldi)

VI.1-HIGH MOLECULAR WEIGHT INORGANIC COMPLEXES Large polymetallic complexes are potentially useful molecules in a variety of areas. Photochemically active compounds are under investigation as efficient photoinitiators for solar-energy conversion, catalysts, and as selective “light-activated anticancer drugs”. On a molecular level, these large organometallic species typically contain light-absorbing units, central electron-collecting units, and bridges between the units. Because of the importance of their chemical structure for optimum operation, the high molecular weight complexes must be thoroughly characterized by analytical techniques. Typical characterization techniques include NMR, electrochemistry, and Xray crystallography. However, NMR spectra are commonly complex and suffer from paramagnetic effects and crystals are often unobtainable. More reliable, rapid characterization is sought. Mass spectrometry should be an effective tool in the structural characterization of these organometallic coordination complexes. However, the low volatility, fragility, and lability of the species have made MS problematic. Significant advances have been made with fast-atom-bombardment mass spectrometry (FAB-MS) and electrospray-ionization mass spectrometry (ESI-MS), although these techniques still have limitations. FAB-MS, for example, has been successful for monometallic and small polymetallic compounds, but fragmentation often causes a low intensity or complete absence of the intact molecular ion in many spectra. ESI-MS suffers from similar problems, and the