Figure 4.

(A) Experimental Mims ENDOR spectra of P1–P6 recorded at the high-field Y position at 20 K. (B) Hyperfine couplings of the H₁ protons along the Y axis of the ZFS tensor (A_Y) determined by Gaussian fitting of the principal hyperfine peak in the experimental ENDOR spectra as a function of oligomer size; the error bars indicate the full width at half-maximum (fwhm). The gray line corresponds to the theoretical N^–1 relationship for the hyperfine couplings in case of complete delocalization. The change of the position of the hyperfine peak with respect to the Larmor frequency between P1 and P2 was explained by a change in the sign of D. The orientation of the ZFS tensor for the linear oligomers is shown in the inset; in P1, the X and Z axes are exchanged.