Colour charge

The electronic spectrum of the complex consists of a combination of the spectra of the parent compounds plus one or more higher wavelength transitions, responsible for the colour. Charge transfer is promoted by a low ionization energy of the donor and high electron affinity of the acceptor. A potential barrier to charge transfer of Va = Id — Ea is predicted. The width of the barrier is related to the intermolecular distance. Since the same colour develops in the crystal and in solution a single donor-acceptor pair should be adequate to model the interaction. A simple potential box with the shape... 

The nitrosonium cation can serve effectively either as an oxidant or as an electrophile towards different aromatic substrates. Thus the electron-rich polynuclear arenes suffer electron transfer with NO+BF to afford stable arene cation radicals (Bandlish and Shine, 1977 Musker et al., 1978). Other activated aromatic compounds such as phenols, anilines and indoles undergo nuclear substitution with nitrosonium species that are usually generated in situ from the treatment of nitrites with acid. It is less well known, but nonetheless experimentally established (Hunziker et al., 1971 Brownstein et al., 1984), that NO+ forms intensely coloured charge-transfer complexes with a wide variety of common arenes (30). For example, benzene, toluene,... 

Diclofenac sodium, famotidine and ketorolac were analysed utilising their formation of a coloured charge transfer complex with 2,4 dichloro-6-nitrophenol. The complexes were detected by UV/visible spectrophotometry at 450 nm. The method was not affected by the presence of common excipients in the formulations analysed. The precision and accuracy of the method was comparable to that of HPLC methods used to analyse the same samples. ... 

A coloured charge transfer complex formed by absorption of ferrocyanide at the surface of Ti02 particles and electrodes, on photo-excitation injects electrons into the conduction band of Ti02 the conduction band electrons can be used to generate a photocurrent (Gratzel, 1987)... 

The six quarks, namely the up quark (u), the down quark (d), the strange quark (s), the charm quark (c), the top quark (t), sometimes also called truth quark, and the bottom quark (b), also dubbed beauty quark, carry a colour charge. The bosons that act on colour, are called gluons, which are the carriers of the colour interaction. The residue of this interaction is the strong nuclear interaction, which is operative between the hadrons (for instance the proton and the neutron within an atomic nucleus). 

Fig. 12.1. The potential between static colour charges versus distance, in dimensionless lattice units. The points represent the Monte Carlo data of Stack (1984). The bold line corresponds to the linear plus Coulomb fit to the data.

Intensely coloured charge-transfer complexes are formed from N0XX.A (X - Al, Ga, Tl X ci F) and benzene or laethyl-substltuted benzenes. The unusual aluminium bls(dlcarbolllde)... 

Butyl-lithium adds to Ph2C rCHj giving a coloured (charge-delocalized) product, which can be written as an ion-pair (at least for donor solvents) ... 

---