Arylamine-substituted oligo(ladder-type pentaphenylene)s: electronic communication between bridged redox centers.
Novel bis(arylamine-substituted) oligo(ladder-type pentaphenylene)s 1-3, with bridge lengths estimated to be 2.2, 4.2, and 6.3 nm, respectively, have been developed, and the model compound 4 with a mono-arylamine substituent was also synthesized. Their absorption spectra in different solvents are almost identical, while distinct bathochromic shifts of the photoluminescence (PL) spectra were observed with increasing solvent polarity due to the polarized excited states. The cyclic voltammetry (CV) and differential pulse voltammetry (DPV) spectra display a two-step oxidation of the bridged diamines in compound 1, which suggests that the electron and charge delocalize in mixed-valence (MV) cation 1+* and that both redox centers can communicate through the pentaphenylene bridge. Only unresolved curves in CV and DPV spectra were observed in the first two oxidation processes of diamines 2 and 3, indicating that the bridges are too long for efficient delocalization over the entire molecules and the radical cations localize at each arylamine center. This finding was further supported by chemical oxidation with SbCl5 and studies of the corresponding UV-vis-NIR absorption spectra of compounds 1-4. A significant intervalence charge-transfer (IVCT) band around 5283 cm-1 (1893 nm) was observed in 1+*. This is the first report of such a highly intense IVCT band in the NIR region with intensity similar to that of the visible band of the radicals, enabling further analysis of the CT process and the coupling matrix element V, classifying 1+* as a class II derivative (V = 1.6 kcal/mol). This study may offer an effective way to improve the understanding of charge transfer and charge-carrier transport in various conjugated oligomers or polymers and facilitate their ongoing exploration in optoelectronic applications.
Zhou
Gang
G
Max-Planck-Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany.
Baumgarten
Martin
M
Müllen
Klaus
K
D000814:Aniline Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D004563:Electrochemistry; D007700:Kinetics; D055095:Optics and Photonics; D010084:Oxidation-Reduction; D011083:Polycyclic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013056:Spectrophotometry, Ultraviolet; D019265:Spectroscopy, Near-Infrared
D000814:Aniline Compounds; D011083:Polycyclic Compounds; C515755:poly(pentaphenylene)