Chromophores General Considerations

The comparison of Fe(III) spin transition systems with those of other metal ions reveals the greater variety of chromophores for which spin crossover is observed in iron(III). This is reflected in a generally more diverse coordination environment as well as a far broader range of donor atom sets. For six-coordinate systems the spin crossover generally involves an S=l/2<->S=5/2 change, whereas for five-coordinate materials an intermediate (quartet) spin state is involved in S=l/2<->S=3/2 transitions. There is just one report of such a transition in a six-coordinate system and that is considerably distorted [126]. 

In a number of cases the molecule under consideration has zero-order degenerate localized states, e.g., two carbonyl groups in a diketone. Interactions between the two chromophores will, in general, lift the zero-order degeneracy. In such a molecule there are, say, two discrete levels coupled... 

The reader will recall equations 9 and 10 are generally ca 5 and 42 kJ moT1 endothermic. However, we generally lack enthalpies of formation for the compounds with the same affixed X as the above with which to compare reactions 9,10 and 16. Possibly, though very unlikely, the reaction of two conjugated dienes to form a linearly conjugated tetraene will show considerable additional stabilization. We note one comparison of related 4 and 3 chromophore species. Consider the de-acetylenation reaction... 

The compounds of the second group will be of primary concern in the following lines. The most important advantage of the application of these fluorescent dyes (fluorophores) in comparison with the ordinary ones (chromophores) is a considerable increase in the nsitivity of protein detection. The introduction of fluorescent dyes in order to increase the sensitivity of the dye techniques is ascribed to Creech and Jones who treated proteins with benzantryl isocyanate to form the corresponding carbamido conju tes. Approximately at the same time, Coons et al. started to apply the fluorescence antibody technique. Since that time this technique is generally... 

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