Metal responsive systems

Despite the considerable amount of information that has been garnered from more traditional methods of study it is clearly desirable to be able to generate, spectroscopically characterize and follow the reaction kinetics of coordinatively unsaturated species in real time. Since desired timescales for reaction will typically be in the microsecond to sub-microsecond range, a system with a rapid time response will be required. Transient absorption systems employing a visible or UV probe which meet this criterion have been developed and have provided valuable information for metal carbonyl systems [14,15,27]. However, since metal carbonyls are extremely photolabile and their UV-visible absorption spectra are not very structure sensitive, the preferred choice for a spectroscopic probe is time resolved infrared spectroscopy. Unfortunately, infrared detectors are enormously less sensitive and significantly slower... 

The molecule is often represented as a polarizable point dipole. A few attempts have been performed with finite size models, such as dielectric spheres [64], To the best of our knowledge, the first model that joined a quantum mechanical description of the molecule with a continuum description of the metal was that by Hilton and Oxtoby [72], They considered an hydrogen atom in front of a perfect conductor plate, and they calculated the static polarizability aeff to demonstrate that the effect of the image potential on aeff could not justify SERS enhancement. In recent years, PCM has been extended to systems composed of a molecule, a metal specimen and possibly a solvent or a matrix embedding the metal-molecule system in a molecularly shaped cavity [62,73-78], In particular, the molecule was treated at the Hartree-Fock, DFT or ZINDO level, while for the metal different models have been explored for SERS and luminescence calculations, metal aggregates composed of several spherical particles, characterized by the experimental frequency-dependent dielectric constant. For luminescence, the effects of the surface roughness and the nonlocal response of the metal (at the Lindhard level) for planar metal surfaces have been also explored. The calculation of static and dynamic electrostatic interactions between the molecule, the complex shaped metal body and the solvent or matrix was done by using a BEM coupled, in some versions of the model, with an IEF approach. 

In this chapter, the unique features of transition metals in biological systems are discussed from the point of view of structural roles, spectroscopic properties, electron transfer, hydrolytic and redox catalysis, and metal-responsive gene expression. The following chapters provide more detail on these subjects. Several important examples not discussed elsewhere in this volume will be presented. The goal of this chapter (and this volume) is to acquaint the reader with the wide range of roles played by metal ions in biological systems and thereby to demonstrate why metals are such useful cofactors and why scientists from such broad disciplines are drawn to study their properties. 

Montgomery, C.R, Murray, B.S., New, E.J., Pal, R., and Parker, D. Cell-penetrating metal complex optical probes targeted and responsive systems based on lanthanide luminescence. Accounts of Chemical Research, 42 (7), 925-937. 

The excitation spectrum should be strongly related to the dielectric response of the metal-molecule system. For a... 

Systems Exhibiting Metal-Responsive Gene Expression... 

---