Excited-State and Photoelectrochemical Behavior of Pyrene-Linked Phenyleneethynylene Oligomer

Abstract

An oligophenyleneethynylene (OPE), 1,4-bis(phenyleneethynyl)-2,5-bis(hexyloxy)benzene (2), is coupled with pyrene to extend the conjugation and allow its use as a light-harvesting molecule [Py-OPE (1)]. The absorption and emission maxima of 1 are red-shifted compared to those of 2. Similar differences in the singlet and triplet excited-state properties are evident. The fluorescence yield of 2 in toluene is 0.53, which is slightly less than the value for the parent OPE (2) of 0.66. The excited singlet and triplet of 1 as characterized from transient absorption spectroscopy exhibit lifetimes of 1.07 ns and 4.0 micros, respectively, in toluene. When 1 was cast as a film on a glass electrode (OTE) and excited with a 387-nm laser pulse, we observed the formation of excitons that decayed within a few picoseconds. When 1 was cast as a film on a SnO2-modified conducting glass electrode (OTE/SnO2), a small fraction of excitons dissociated to produce a long-lived charge-separated state. The role of the SnO2 interface in promoting charge separation was inferred from the photoelectrochemical measurements. Under visible light excitation, the OTE/SnO2 electrode was capable of generating photocurrent (approximately 0.25 mA/cm2) with an incident photon conversion efficiency (IPCE) of approximately 6%.

Double Molecular Antenna Pyrene – Bridge - Fullerene C60

“…(2) shows the UV-Vis spectra of compounds 3 and 6 in CHCl 3 . Two main peaks can be found at around 330 and 350 nm, in the same positions as they are observed for pyrene [19]. The UV absorptions from C 60 cannot be distinguished, as they are likely overlapped by the pyrene bands.…”

“…For the C 60 triads 8 and 9, for both cases of excitation on the pyrene bands (338 nm) or on the * conjugation broad absorption (385 nm), two sharp peaks are detected at 393 nm and 413 nm (Fig. 6), as for pyrene monomer emission [19,20]. The vibronic spacing is 1230 cm -1 , consistent with the stretching modes of an aromatic nucleus.…”

Organic Polyaromatic Hydrocarbons as Sensitizing Model Dyes for Semiconductor Nanoparticles

“…The inho- More recently, Kamat and co-workers have studied the excited-state properties of pyrene-linked phenyleneethynylene oligomers in solution, and probed their photoelectrochemical behavior bound to a conducting glass electrode (OTE) and to a SnO 2 -modified conducting glass electrode (OTE/SnO 2 ). [53] Py-OPE did retain several of the photophysical characteristics of the parent oligomer (OPE), and the pyrene chromophore in Py-OPE exhibited the same kind of spectral and photophysical changes observed in other aromatic-OPE systems: high fluorescence quantum yields, absorption and emission bands shifted to longer wavelengths, and enhanced exctinction coefficients ( Figure 15).…”

“…This is consistent with the studies reported by Thomas and Kamat described below, [51] and also by others. [52,53] The Py-OPE-Ipa sensitizers exhibited an unexpected behavior: an increase in the pyrene fluorescence quantum yield to near unity and a 100-fold decrease in the excited-state lifetime. ZINDO/S configuration interaction (CI) calculations helped to rationalize this behavior as the consequence of the reversal in the order of the two lowest-lying singlet excited states of pyrene: the forbidden 1 B 2u and the allowed 1 B 3u state, upon substitution with a p-phenylethynyl unit in position 1 on the pyrene unit.…”

Photoluminescence behaviors of organic soluble DNA bearing carbazole and pyrene derivatives as side‐chain substituents and effect of the copolymer structure on the Förster energy transfer process

“…Compounds 1 , 2 , 4 , and diethyl pyrene‐1‐ylmethylphosp were synthesized by following the literature methods 15–22…”