Do [all]-S,S′-Dioxide Oligothiophenes Show Electronic and Optical Properties of Oligoenes and/or of Oligothiophenes?

Abstract

A comprehensive photophysical and spectroscopic (electronic and Raman) study guided by density functional theory, DFT, CIS, and correlated ab initio calculations has been performed on a series of fully oxidized oligothiophenes with variable chain length, and up to four rings. A comparison with the properties of oligoenes and oligothiophenes is proposed. Absorption, fluorescence, lifetimes, flash-photolysis, phosphorescence, two-photon absorption, Raman, resonance Raman, and thermospectroscopy data are collected and interpreted according to the obtained theoretical results. The interest is focused on the ground electronic state and in the low-lying excited electronic states. Full oxygenation of the sulfur atoms of oligothiophenes results in: (i) restricted inter-ring isomerization such as observed from the absorption spectra; (ii) an effective quenching of fluorescence, and (iii) the appearance of dual emission. The emission features are explained by the interference of a dipole-allowed and a dipole-forbidden singlet excited states leading to simultaneous lighting from a local Frenkel and an intramolecular charge transfer photon-releasing configurations. These two excited states contribute to the broadening of the light emission spectrum. These properties highlight the similarity of these samples to that of oligoenes with comparable number of π-electrons.

Tuning the polarity of charge carriers using electron deficient thiophenes

“…The spectra of all the pentamers are broad and show no vibronic fine structure, in contrast to fully oxidized thiophene-1,1-dioxide oligomers that have vibronic features due to their rigidity. 46 The cyclic voltammograms of all the pentamers show clear reduction and oxidation peaks, and have good redox stability over several cycles (Fig. S4†), apart from TTTTT which shows no reduction peak within the solvent window.…”

Organic Semiconductors and Conductors with tert-Butyl Substituents

“…The former two are new compounds, though several alkyl-substituted TTF and pentacene molecules have been reported [9][10][11][12]. Although alkyl-substituted oligothiophenes have been extensively studied [13], the tert-butyl substituted 4T has been studied to some extent only in the S-dioxide form [14]. We have also investigated the structural and conducting properties of the TCNQ complex of (1).…”

Mechanistic Investigations of Organic Aggregates with Different Topologies for Optical Limiting Applications

“…Measurements with these materials have been carried out in conjunction with the design and fabrication of new quinoidal oligothiophenes, [11][12][13] circular molecular systems, [2][3][4][5][6][7][8] Fe-, Ru-, 8 Pt-complexes, 19,20 and small metal nanoparticle systems [21][22][23][24] as to provide a direct feed back to the understanding of the structure/function relationships. Due to biradical character of the ground state for quinoidal oligomers these systems open new avenue in the design of highly responsive optical limiting materials covering very broad spectral range up to 2200nm.…”