Wavefunction oligomer

The PTA oligomers have been substituted with the electron donating dimeth-ylaniline and electron accepting nitrophenyl either in symmetric or asymmetric geometry (Fig. 19). In the short substituted PTAs the donor and acceptor groups have a significant influence on the electronic wavefunctions on the backbone which is portrayed by the shift of about 100 nm of the absorption spectra to the red compared to the pure PTA. 

Figure 4-2. INDO/SCI-simulated linear absorption spectrum of the eleven-ring PPV oligomer. The vertical lines represent the oscillator strength of the transitions that are described the site labeling used for the wavefunction analyses is shown on top.

F re 4-3. Absolute values of the INDO/SCl-calculated electron wavefunctions y/(x, X), = 34) calculated for the eleven-ring PPV oligomer as a function of carbon site (hole fixed on site 34) for the excited states corresponding to (a) the first absorption peak (3.0 eV) (b) the second absorption peak (3.8 eV) (c) the third absorption peak (5.6 eV) (d) the fourth absorption peak (6.3 eV) and (e) the fifth absorption peak (7.0 eV). The energies given between parentheses refer to the theoretical values. 

Figure 4-8. INDO/SCI simulation of the wavefunction i// xe,Xk = 16, chain I) of the lowest charge transfer-excited state in a cofacial dimer formed by two five-ring PPV oligomers separated by 4 A. t// xe,xi, = 16, chain 1) represents the probabdity amplitude in finding an electron on a given site Xe assuming the hole is centered on site 16 of chain 1. The site labeling is the same as that reported on top of Figure 4-7.

The transition dipole vector for the oligomer s absorption band associated with excitOTi wavefunction Vg is obtained by summing over the monomer transitions ... 

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