Systems Explored

As has already been discussed, there are three key requirements of ligands for use in the sensitized luminescence of lanthanides  

Various approaches have been taken to the synthesis of effective luminescent materials, using a variety of large encapsulating antenna-containing ligands, including podands, calixarenes, macrocycles, and macrobicycles (cryptands). These have been divided into acyclic (sub-section A) and cyclic (sub-section B). Representative ligands and complexes will be presented and discussed. 

A number of ligands containing benzimidazole chromophores have been developed, and coordinated with lanthanide(III) ions. Reaction 

The unsymmetrical derivative, L2, in which one benzimidazole group is replaced by a 2-pyridyl moiety, and its complexes with europium and terbium have been further studied for their photophysical properties (37). The coordinated nitrate anions in the [ ( 2)( ) ] 

Related complexes where two ligands encapsulate the lanthanide center have been reported (38,39). Coordination of a second antenna ligand may increase the luminescence by excluding deactivating solvent molecules to date, however, photophysical studies for these complexes have not been published. A recent paper details ternary complexes with an additional chromophore, antipyrene (antipy) 

A number of other acyclic ligand systems have been developed that use tris(aminoethyl)amine (tren) as a central unit (for macrobicycles 

The parent ligand tris(pyrazolyl)borate, [L ] , forms 1 1 and 1 2 metahligand complexes [Ln(L )(N03)2] and [Ln(L )2]the molecular structure of the latter is shown in Pig. 6. In solution, dissociation of the nitrate anions in the former complex leave the lanthanide ion open to coordination by solvent molecules (47). Photophysical studies in water and methanol (48) confirm this use of the Horrocks equation 

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The emerging new sciences of complexity and complex adaptive systems explore the important question of whether (and/or to what extent) does the behavior of the many seemingly disparate complex systems found in nature-from the very small to the very large-stem from the same fundamental core set of universal principles. 

So-called reverse ATRP has been described where a conventional radical initiator (e.g. AIBN) and a transition metal complex in its Higher oxidation state are used. 85"288 One of the first systems explored was ( uBr- 133 AIBN VI VIA. It is important that the initiator is completely consumed early in the polymerization. The use of peroxide initiators in reverse ATRP can be problematical depending on the catalyst used and the reaction temperature.286 289 The system CuBr2/133/BPO/MMA at 60°C was found to provide no control,286 In ATRP at lower temperatures (40 °C), the system CuCl/133/BPO/MMA was successful though dispersities obtained were relatively broadf89 Radicals are produced from the redox reaction between the catalyst in its reduced form and BPO. 

Oro J, Squyres SW, Reynolds RT, Mills TM (1992) Europa Prospects for an Ocean and Exobi-ological Implications. In Carle GC, Schwartz DE, Huntington JL (Eds.) Exobiology in Solar System Exploration. NASA SP 12, p 103... 

The three-component coupling systems explored extensively by Zhu has been used to synthesize tricyclic azaindole derivatives 153 from 150, heptanal 151, and an aryl- or alkylamine 152 (Equation 35) <20050L239>. 

The systems explored above illustrate a very important point about the control of openloop unstable systems the control of these systems becomes more difficult as the order of the system is increased and as the magnitudes of the first-order lags increase. 

The second experimental system explored the reduction mechanism of another azo-dye, known as Sudan III (I-(4-pheuyIazophenyIazo)-2-naphthoI) [91]. Sudan III contains two azo groups rendering two successive two-electron, two-proton reduction steps at the mercury surface. Figure 2.68 shows a typical SW voltammetric response of Sudan III recorded in a borate buffer at pH 10.00. The first reduction step is chemically reversible, while the second one is irreversible. More importantly, the second reduction step proceeds at potential about 230 mV more negative than the first one, thus causing a well-separated voltammetric peak. The overall mechanism... 

Younger, P. L., Jayaweera, A. et al. 2003. Passive treatment of acidic mine waters in subsurface-flow systems exploring RAPS and permeable reactive barriers. Land Contamination and Reclamation, 11, 127-135. 

Other Jahn-Teller systems explored through DFT 455... 

OTHER JAHN-TELLER SYSTEMS EXPLORED THROUGH DFT 4.1. Cu2+ doped cubic oxides... 

Cooper JF (2001) Jovian magnetospheric irradiation effects on Europa surface composition. In Greeley R (ed) Europa focus group workshop 1, pp 6-7. Available at http //astrobiology.asu.edu/focus/europa/intro.html Cooper JF, Phillips CB, Green JR, Wu X, Carlson RW, Tamppari LK, Terrile RJ, Johnson RE, Eraker JH, Makris NC (2002) Europa exploration science and mission priorities for 2003-2013 and beyond. In Sykes MV (ed) ASP Conference Series the future of solar system exploration, 2003-2013, ASP, San Francisco, pp 1-36... 

The next tubular reactor system explored is one with co-current flow of coolant. The same cooled reactor used in the previous section is used. It has 500 tubes packed with 39,260 kg of catalyst. Each tube is 0.1 m in diameter and 10 m in length. 

This work was supported by the National Aeronautics and Space Administration jointly through the Exobiology Program of the Life Sciences and the Planetary Geology Program of the Solar System Exploration Divisions. 

The search for signs of life, present or past, is an important goal of NASA s robotic solar system exploration programs and, ultimately, for its astronomical programs designed to probe the gross characteristics of extrasolar planetary systems. To date, that search has been governed by a model of life that is based on the life that we know on Earth—terran life. Several features of terran life have attracted particular focus ... 

After initial findings that some enzymes were active and stable in SCF s [1,2], several other studies on enzyme catalysis in SCF s have been carried out. The majority of systems explored to date have used model reactions [3,4] of which only a few show a possibility for practical and commercial purposes [5],... 

It is most probable that in the next few years we are going to witness an exponaitial increase of these kinds ofab initio molecular dynamics simulations on more and more complicated catalytic systems, exploring complex reaction mechanisms. One of the challenges in this respect is the use of special molecular dynamics simulation techniques adapted to activated processes, which could be the appropriate tool for the theoretical prediction of rate constants. 

This property is satisfied by the system illustrated in Section II and every other system explored with the same method in the present volume. 

We may look at atomic clusters as particularly apt and useful models to study virtually every aspect of what we call, diffusely, complexity. Simulations are particularly powerful means to carry out such studies. For example, we can follow trajectories for very long times with molecular dynamics and thereby evaluate the global means of the exponential rates of divergence of neighboring trajectories. This is the most common way to evaluate those exponents, the Liapunov exponents. The sum of these is the Kolmogorov entropy, one gross measure of the volume of phase space that the system explores, and hence one... 

Rietmeijer, F.J.M. Karner, J.M. Metastable eutectics in the AI2O3 - SiO2 system explored by vapor phase condensation. J. Chem. Phys. 1999, 110, 4554-4558. 

Corezzi, S., Lucchesi, M., Rolla P. A., Capaccioli, S., Gallone, G. (1999) Temperature and pressure dependences of the relaxation dynamics of supercooled systems explored by dielectric spectroscopy, Phil. Mag. B 79, 1953-1963... 

Solar System Exploration. Available online. URL http //... 

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