Multichromophoric systems Chromophores

Multichromophoric systems consisting of two benzoate chromophores and another chro-mophore are subject to additivity relation in the amplitudes of exciton Cotton effects145, similar to that found for polybenzoate systems (Section 4.4.2.4.). 

Nevertheless, other chromophores have been investigated and they have provided interesting insights, particularly porphyrin and Cso groups, since these serve as useful mimics of the cofactors present in the photosynthetic reaction center (Figure 37). Electron transfer involving porphyrins and fullerenes will be presented in more detail elsewhere in this Handbook Volume III, Part 2, Chapter 2 and Volume II, Part 1, Chapter 5 respectively), and so only a brief discussion is presented here. An excellent overview of photoinduced ET processes in Cso-based multichromophoric systems has been produced previously [116]. 

Information about the rate constant of hopping ( hopp) through excitation energy transfer can be derived from the fast anisotropy decay time (02)- In order to take into account the possibility of multiple energy transfer channels in the case of a multichromophoric system containing identical chromophores, among which efficient dipole-dipole interactions occur, the measured anisotropy decay time 02 can be related to fchopp by Eq. (5), where the value of i represents the number... 

The study of complex multichromophoric systems, for which the interpretation of the spectra is facilitated because emission usually takes place exclusively from one of the chromophores. 

Generally speaking, an antenna for light harvesting is an organized multicomponent system in which several chro-mophoric molecular species absorb the incident light and channel the excitation energy to a common acceptor component. Artificial antenna systems based on porphyrin arrays [63], multichromophoric cyclodextrins [64], polynuclear metal complexes [65, 66], dendrimers [66-68], and polymers [69, 70] have been reported. In all these systems, the chromophoric units are connected by means of covalent... 

---