Aggregation of 3,4,9,10-Perylenediimide Radical Anions and Dianions Generated by Reduction with Dithionite in Aqueous Solutions

Abstract

Aqueous solutions of N,N'-bis(2-phosphonoethyl)-3,4,9,10-perylenediimide (PPDI) were titrated with sodium dithionite, generating radical anions (PPDI(-*)) and dianions (PPDI(2-)). In aqueous ethanol (1:1 v/v), PPDI existed as monomers and remained in the monomeric form in all reduced states. In water, on the other hand, PPDI formed dimers, which were transformed into a pi-stacked aggregated form upon one-electron reduction to PPDI(-*). Addition of a second electron, however, resulted in dissociation of the aggregates, giving the dianion PPDI(2-) in the monomeric form. The presence of CTAB micelles prevented the aggregation of PPDI(-*) in water, indicating that the radical anions were incorporated into the micellar phase. Reduction of PPDI in ethanol solution, where the dye was aggregated, resulted in the formation of soluble mixed stacks containing both PPDI(-*) and PPDI(2-). These mixed stacks stabilized the radical anion form, preventing further reduction to the dianion.

Self-sorted photoconductive xerogels

“…For xerogel- 1 , 2 , two prominent transient bands are observed (at 725 and 830 nm) showing indistinguishable decay kinetics on the 10 ps to >3 ns timescale. The spectrum of this newly photogenerated species is in excellent agreement with that previously reported for the PBI˙ – of 1 , 27,51,52 indicating that charge separation and formation of the conductive states occurs within 10 ps of excitation of 1 and approximately 40% of the PBI˙ – persists beyond 3 ns (compared to the concentration at 10 ps), Fig. 10d.…”

“…This is readily assigned to the formation of the radical anion of 1 through comparison to literature precedent. 27,51,52 Importantly, irradiating xerogel- 1 with 450 nm light did not result in the formation of the radical anion (Fig. S10, ESI†), explaining the lack of conductivity at this wavelength.…”

Multimode simulation of dimer absorption spectra from first principles calculations: Application to the 3,4,9,10-perylenetetracarboxylic diimide dimer

“…The effects of the solvent described with the IEFPCM approach lead to a decrease of about 0.1 eV at both computational levels. Thus, the vertical excitation energy in water, calculated with TD-DFT at 2.33 eV, is found in very good agreement with the experimental maximum of absorption 26 in water/ethanol reported at 2.35 eV. Such good agreement between theory and experiment for the PDI monomer was already noted in recent studies.…”

“…The simulated absorption spectrum in vacuum is compared to the experimental spectrum in water/ethanol taken from Ref. 26. It is seen that the relative position and intensities of the simulated vibronic bands are in very good agreement with experiment.…”

“…20 Indeed, such compounds are used in a variety of applications like for example in solar cells 21,22 or photoinduced electron transfer systems. 23,24 Moreover, PDI's chromophores are known to easily form dimers in solution 25,26 and both monomer and dimer absorption spectra show a well-resolved vibronic structure. Consequently, the PDI chromophore is an ideal compound for applying and testing our computational approach.…”