Robust ethylenedioxythiophene-vinylene oligomers from fragile thiophene-vinylene cores: synthesis and optical, chemical and electrochemical properties of multicharged shapes

[All]-S,S-dioxide Oligo-Thienylenevinylenes: Synthesis and Structural/Electronic Shapes from Their Molecular Force Fields

Oligo-S,S-dioxothienylenevinylenes have been prepared by transferring oxygen atoms to the sulfur atoms using the HOF⋅CH₃ CN complex. Their photophysical properties are presented in comparison with their thiophenevinylene congeners. Together with their vibrational properties and molecular force fields, this study allows for the interpretation of the alteration of aromaticity and inter-ring exocyclic π-conjugation in this series.

Thieno[3,4-c]pyrrole-4,6-dione Oligothiophenes Have Two Crossed Paths for Electron Delocalization

A new series of electron-deficient oligothiophenes, thieno[3,4-c]pyrrole-4,6-dione oligothiophenes (OTPD_n ), from the monomer to hexamer, is reported. The optical and structural properties in the neutral states have been analyzed by absorption and emission spectroscopy together with vibrational Raman spectroscopy. In their reduced forms, these molecules could stabilize both anions and dianions in similar ways. For the dianions, two independent modes of electron conjugation of the charge excess were observed: the interdione path and the interthiophene path. The interference of these two paths highlighted the existence of a singlet diradical ground electronic state and the appearance of low-energy, thermally accessible triplet states. These results provide valuable insights into the device performance of TPD-based materials and for the rational design of new high-performance organic semiconductors.

Oligothienylenevinylene Polarons and Bipolarons Confined between Electron-Accepting Perchlorotriphenylmethyl Radicals

A detailed analysis is undertaken of positively charged species generated on a series of thienylenevinylene (nTV) wires terminally substituted with two perchlorotriphenylmethyl (^. PTM) radical acceptor groups, ^. PTM-nTV-PTM^. (n=2-7). Motivated by the counterintuitive key role played by holes in the nTV bridges on the operating mechanism of electron transfer in their radical anion mixed-valence derivatives, a wide combination of experimental and theoretical techniques is used, with the aim of gaining further insights into their structural location. Consequently, contributions of the ^. PTM units for the stabilization of the radical cations and hole localization, particularly in the case of the shortest molecular wire, are probed. In this sense, the formation of quinoidal ring segments, resulting from the coupling of the unpaired electron of the ^. PTM radical site with those generated along the nTV chains is found. Additionally, open-shell dications, described by the recovery of the central aromaticity and two terminal quinoidal segments, assisted by the ^. PTM units, are detected.

Stable Radical Cations and Their π-Dimers Prepared from Ethylene- and Propylene-3,4-dioxythiophene Co-oligomers: Combined Experimental and Theoretical Investigations

Co-oligomers composed of two 3,4-ethylenedioxythiophene (EDOT) units and two or three 3,4-propylenedioxythiophene (ProDOT) units, i.e., 2E2P_Et and 2E3P_Et, were newly synthesized together with the ProDOT trimer 3P_Me. On the basis of cyclic voltammetry, the gaps between the first and second oxidation potentials (ΔE^1-2) of 2E2P_Et and 2E3P_Et were found to be larger than that of the previously synthesized ProDOT tetramer 4P_Hex. These co-oligomers gave the fairly stable radical cations 2E2P_Et^•+ and 2E3P_Et^•+ by chemical oxidation with AgSbF₆. The disproportionation of 2E2P_Et^•+ and 2E3P_Et^•+ into neutral and dicationic species, which was observed for 4P_Hex^•+, was inhibited in accord with the larger ΔE^1-2. Additionally, the formation of the π-dimers (3P_Me)₂²⁺, (2E2P_Et)₂²⁺, and (2E3P_E)₂²⁺ was clearly observed in dichloromethane solution at low temperatures with UV-vis-NIR spectroscopy. Furthermore, the π-dimerization enthalpies of 2E2P_Et^•+ and 2E3P_Et^•+ were greater than that of 3P_Me^•+, suggesting the formation of fully π-contacted structures. The structures of the π-dimers were optimized at the B97D3 method, and the calculated absorption spectra of the π-dimers obtained using TD-DFT methods were in reasonable agreement with the observed ones, supporting the reliability of the calculated structures.

Design of Assembled Systems Based on Conjugated Polyphenylene Derivatives and Carbon Nanohorns

Promising materials have been designed and fully characterised by an effective interaction between versatile platforms such as carbon nanohorns (CNHs) and conjugated molecules based on thiophene derivatives. Easy and non-aggressive methods have been described for the synthesis and purification of the final systems. Oligothiophenephenylvinylene (OTP) systems with different geometries and electron density are coupled to the CNHs. A wide range of characterization techniques have been used to confirm the effective interaction between the donor (OTP) and the acceptor (CNH) systems. These hybrid materials show potential for integration into solar cell devices. Importantly, surface-enhanced Raman spectroscopy (SERS) effects are observed without the presence of any metal surface in the system. Theoretical calculations have been performed to study the optimised geometries of the noncovalent interaction between the surface and the organic molecule. The calculations allow information on the monoelectronic energies of HOMO-LUMO orbitals and band gap of different donor systems to be extracted.

Free-base porphyrin and [60]fullerene linked by oligomeric ethylenedioxythienylenevinylene bridge

The synthesis and structural characterization and the study of the electronic properties of two novel porphyrin-bridge-fullerene molecules, where a free-based porphyrin and [60]fullerene are connected through one and two units of ethylenedioxythienylenevinylene π-conjugated bridges, is reported. The absorption studies, voltamperometric measurements and theoretical calculations at DFT level are presented. A HOMO–LUMO gap as low as 1.41 eV has been found for compound 6.