Effective conjugation length and UV/vis spectra of oligomers

Abstract

On the basis of an extended series of monodisperse oligomers of the dialkoxy-substituted phenyleneethenylenes la-i the Eqs.(3) and (4) were conceived in order to determine the limiting values of the energies Ei and the wavelengths di of the W / v i s absorption. The convergence of the Ei and l i values with a growing number n of repeating units pennits a precise prediction of the Ei,,,, and ,Ii,,,, values of the corresponding polymer 1 j as well as a statement about the overall effect of conjugation mi and the effective conjugation length ECL. A great variety of different conjugated oligomers 2-14 can be evaluated by the same algorithm. Acta Polymer., 48,379-384 Q VCH Verlagsgesellschaft mbH, D-69451 Weinheim 1997 0323-7648/97/0808-0379$17.50+.50/0 Acta Polymer., 48,379-384 (1997) Effective conjugation length and UV/vis spectra of oligomers 383

Hole-vibronic coupling in oligothiophenes: impact of backbone torsional flexibility on relaxation energies

“…We found that the best fit of the data as a function of chain length, n, is obtained when assuming an exponential dependence 1Þ with IP N , A and t being fitting parameters; IP N can be recognized as the polymer (infinite chain) ionization potential. A similar equation has been used before to describe the optical spectra (Meier et al 1997;Gierschner et al 2006). The HOMO energy was also used to estimate the ionization potential in the framework of Koopmans' (1933) theorem.…”

Conformational disorder and energy migration in MEH-PPV with partially broken conjugation

“…The inhomogeneous broadening of the site energies was introduced via a Gaussian distribution of the transition energies of the spectroscopic units. The energy of a spectroscopic unit has also been correlated to its length using the energies given for MEH-PPV-like oligomers in chloroform reported by Meier et al 40 Figs. 3͑a͒ and 3͑b͒.…”

Synthesis and properties of oligo(2,5-thienylene-ethynylene)s

“…1u, 43 The parameters a and b, respectively, have to be optimized on the basis of the measured λ max (n). Normally, four data points are sufficient for an accurate prediction of λ ∞ .…”