Stable and soluble oligo(3,4-ethylenedioxythiophene)s end-capped with alkyl chains

Fabrication of Flexible Wiring with Intrinsically Conducting Polymers Using Blue-Laser Microstereolithography

Recently, flexible devices using intrinsically conductive polymers, particularly poly(3,4-ethylenedioxythiophene) (PEDOT), have been extensively investigated. However, most flexible wiring fabrication methods using PEDOT are limited to two-dimensional (2D) fabrication. In this study, we fabricated three-dimensional (3D) wiring using the highly precise 3D printing method of stereolithography. Although several PEDOT fabrication methods using 3D printing systems have been studied, few have simultaneously achieved both high conductivity and precise accuracy. In this study, we review the post-fabrication process, particularly the doping agent. Consequently, we successfully fabricated wiring with a conductivity of 16 S cm^-1. Furthermore, flexible wiring was demonstrated by modeling the fabricated wiring on a polyimide film with surface treatment and creating a three-dimensional fabrication object.

Electron‐Rich EDOT Linkers in Tetracationic bis‐Triarylborane Chromophores: Influence on Water Stability, Biomacromolecule Sensing, and Photoinduced Cytotoxicity

Three novel tetracationic bis‐triarylboranes with 3,4‐ethylenedioxythiophene (EDOT) linkers, and their neutral precursors, showed significant red‐shifted absorption and emission compared to their thiophene‐containing analogues, with one of the EDOT‐derivatives emitting in the NIR region. Only the EDOT‐linked trixylylborane tetracation was stable in aqueous solution, indicating that direct attachment of a thiophene or even 3‐methylthiophene to the boron atom is insufficient to provide hydrolytic stability in aqueous solution. Further comparative analysis of the EDOT‐linked trixylylborane tetracation and its bis‐thiophene analogue revealed efficient photo‐induced singlet oxygen production, with the consequent biological implications. Thus, both analogues bind strongly to ds‐DNA and BSA, very efficiently enter living human cells, accumulate in several different cytoplasmic organelles with no toxic effect but, under intense visible light irradiation, they exhibit almost instantaneous and very strong cytotoxic effects, presumably attributed to singlet oxygen production. Thus, both compounds are intriguing theranostic agents, whose intracellular and probably intra‐tissue location can be monitored by strong fluorescence, allowing switching on of the strong bioactivity by well‐focused visible light.

Donor–acceptor π-conjugated polymers based on terthiophene-3,4-dicarboxylate, dithienopyrrolobenzothiadiazole and thieno[3,4-c]pyrrole-4,6-dione units and their hole mobility

We have synthesized three different p-type donor–acceptor π-conjugated polymers based on diethyl [2,2′:5′,2′′-terthiophene]-3′,4′-dicarboxylate, dithienopyrrolobenzothiadiazole and thieno[3,4-c]pyrrole-4,6-dione units.

Studies of a bola-type bis(dithiafulvene) molecular system: synthesis, crystal structure, and electrochemical properties

A bis(dithiafulvene) compound that contains a 1,3-diphenoxypropane central unit was designed and investigated in this work.

Conjugation Length Effect on the Conducting Behavior of Single-crystalline Oligo(3,4-ethylenedioxythiophene) (nEDOT) Radical Cation Salts

The conjugation length is a unique structural factor for oligomer-based π-conjugated conductors as it modulates their electronic structures. Herein, we demonstrated the conjugation length effects on conductivity by comparing a...

The Simplest Model for Doped Poly(3,4-ethylenedioxythiophene) (PEDOT): Single-crystalline EDOT Dimer Radical Cation Salts

Although doped poly(3,4-ethylenedioxythiophene) (PEDOT) is extensively used in electronic devices, their molecular-weight distributions and inadequately defined structures have hindered the elucidation of their underlying conduction mechanism. In this study, we introduce the simplest discrete oligomer models: EDOT dimer radical cation salts. Single-crystal structural analyses revealed their one-dimensional (1D) columnar structures, in which the donors were uniformly stacked. Band calculations identified 1D metallic band structures with a strong intracolumnar orbital interaction (band width W≈1 eV), implying the origin of the high conductivity of doped PEDOT. Interestingly, the salts exhibited semiconducting behavior reminiscent of genuine Mott states as a result of electron-electron repulsion (U) dominant over W. This study realized basic models with tunable W and U to understand the conduction mechanism of doped PEDOT through structural modification in oligomers, including the conjugation length.

Conjugation-broken thiophene-based electropolymerized polymers with well-defined structures: effect of conjugation lengths on electrochromic properties

The present work highlights the links between electrochromic properties and conjugation-broken thiophene polymers with well-defined structures.

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.

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.

Charge transfer dynamics in DNA revealed by time-resolved spectroscopy

In the past few decades, charge transfer in DNA has attracted considerable attention from researchers in a wide variety of fields, including bioscience, physical chemistry, and nanotechnology. Charge transfer in DNA has been investigated using various techniques. Among them, time-resolved spectroscopic methods have yielded valuable information on charge transfer dynamics in DNA, providing an important basis for numerical practical applications such as development of new therapy applications and nanomaterials. In DNA, holes and excess electrons act as positive and negative charge carriers, respectively. Although hole transfer dynamics have been investigated in detail, the dynamics of excess electron transfer have only become clearer relatively recently. In the present paper, we summarize studies on the dynamics of hole and excess electron transfer conducted by several groups including our own.

Synthesis of Hetero-bifunctional, End-Capped Oligo-EDOT Derivatives

Conjugated oligomers of 3,4-ethylenedioxythiophene (EDOT) are attractive materials for tissue engineering applications and as model systems for studying the properties of the widely used polymer poly(3,4-ethylenedioxythiophene). We report here the facile synthesis of a series of keto-acid end-capped oligo-EDOT derivatives (n = 2-7) through a combination of a glyoxylation end-capping strategy and iterative direct arylation chain extension. Importantly, these structures not only represent the longest oligo-EDOTs reported but are also bench stable, in contrast to previous reports on such oligomers. The constructs reported here can undergo subsequent derivatization for integration into higher-order architectures, such as those required for tissue engineering applications. The synthesis of hetero-bifunctional constructs, as well as those containing mixed-monomer units, is also reported, allowing further complexity to be installed in a controlled manner. Finally, we describe the optical and electrochemical properties of these oligomers and demonstrate the importance of the keto-acid in determining their characteristics.

Exploring the electrochromic properties of poly(thieno[3,2-b]thiophene)s decorated with electron-deficient side groups

Electron-deficient cyanophenyl side groups decrease the response time and drastically improve the stability of electrochromic polymers.

Sequence-Dependent Photocurrent Generation through Long-Distance Excess-Electron Transfer in DNA

Given its well-ordered continuous π stacking of nucleobases, DNA has been considered as a biomaterial for charge transfer in biosensors. For cathodic photocurrent generation resulting from hole transfer in DNA, sensitivity to DNA structure and base-pair stacking has been confirmed. However, such information has not been provided for anodic photocurrent generation resulting from excess-electron transfer in DNA. In the present study, we measured the anodic photocurrent of a DNA-modified Au electrode. Our results demonstrate long-distance excess-electron transfer in DNA, which is dominated by a hopping mechanism, and the photocurrent generation is sequence dependent.

Dynamics of Excess-Electron Transfer through Alternating Adenine:Thymine Sequences in DNA

This paper presents the results of an investigation into the sequence-dependent excess-electron transfer (EET) dynamics in DNA, which plays an important role in DNA damage/repair. There are many published studies on EET in consecutive adenine:thymine (A:T) sequences (Tn), but those in alternating A:T sequences (ATn) remain limited. Here, two series of functionalized DNA oligomers, Tn and ATn, were synthesized with a strongly electron-donating photosensitizer, a trimer of ethylenedioxythiophene (3 E), and an electron acceptor, diphenylacetylene (DPA). Laser flash photolysis experiments showed that the EET rate constant of AT3 is two times lower than that of T3 due to the lack of π-stacking of Ts in AT3. Thus, it was indicated that excess-electron hopping is affected by the interaction between LUMOs of nucleotides.

How Does Guanine-Cytosine Base Pair Affect Excess-Electron Transfer in DNA?

Charge transfer and proton transfer in DNA have attracted wide attention due to their relevance in biological processes and so on. Especially, excess-electron transfer (EET) in DNA has strong relation to DNA repair. However, our understanding on EET in DNA still remains limited. Herein, by using a strongly electron-donating photosensitizer, trimer of 3,4-ethylenedioxythiophene (3E), and an electron acceptor, diphenylacetylene (DPA), two series of functionalized DNA oligomers were synthesized for investigation of EET dynamics in DNA. The transient absorption measurements during femtosecond laser flash photolysis showed that guanine:cytosine (G:C) base pair affects EET dynamics in DNA by two possible mechanisms: the excess-electron quenching by proton transfer with the complementary G after formation of C(•-) and the EET hindrance by inserting a G:C base pair as a potential barrier in consecutive thymines (T's). In the present paper, we provided useful information based on the direct kinetic measurements, which allowed us to discuss EET through oligonucleotides for the investigation of DNA damage/repair.

Functionalized branched EDOT-terthiophene copolymer films by electropolymerization and post-polymerization "click"-reactions

The electrocopolymerization of 3,4-ethylenedioxythiophene (EDOT) with the branched thiophene building block 2,2':3',2″-terthiophene (3T) is presented as a versatile route to functional polymer films. Comparisons to blend systems of the respective homopolymers PEDOT and P3T by in situ spectroelectrochemistry and Raman spectroscopy prove the successful copolymer formation and the access to tailored redox properties and energy levels. The use of EDOT-N3 as co-monomer furthermore allows modifications of the films by polymer analogous reactions. Here, we exemplarily describe the post-functionalization with ionic moieties by 1,3-dipolar cycloaddition ("click"-chemistry) which allows to tune the surface polarity of the copolymer films from water contact angles of 140° down to 40°.

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

Oligomers of ethylendioxythiophene-vinylene have been prepared. Their optical, electrochemical and chemical properties have been studied in detail by absorption and emission spectroscopy as well as cyclic voltammetry, Raman techniques and spectroelectrochemistry complemented with quantum chemical calculations. A comparison with their non-ethylendioxy and non-vinylene parents has been done. The inclusion of the EDO plus the vinylene function generates more robust electronic ground states regarding the largely flexible thiophene-vinylene (n TV) oligomeric homologues. The redox features of the new compounds are also rich of oxidative processes arising as an interesting stabilising balance effect between the oxygen fragment in the EDO groups (mesomeric effect) and the linear π-conjugated structure. The oxidised species have been characterised, which show the ability for the formation of mixed valence charge-transfer complexes and π dimers of different oxidation states, in particular, in the electrochemical medium, resulting that the electrochemical response is accounted for a succession of aggregation and electron-transfer steps. With this work, a full understanding of the optical and electronic properties of these new oligomers in the context of the oligomer approach has been proposed.

Bis-EDOT end capped by n-hexyl or n-hexylsulfanyl groups: the effect of the substituents on the stability of the oxidized states

Sulfur atoms of hexylsulfanyl groups stabilize the radical cation and dication states and prevent the σ-dimerization of the radical cation.

Driving force dependence of charge separation and recombination processes in dyads of nucleotides and strongly electron-donating oligothiophenes

Charge transfer in DNA has attracted great attention of scientists because of its importance in biological processes. However, our knowledge on excess-electron transfer in DNA still remains limited in comparison to numerous studies of hole transfer in DNA. To clarify the dynamics of excess-electron transfer in DNA by photochemical techniques, new electron-donating photosensitizers should be developed. Herein, a terthiophene and two 3,4-ethylenedioxythiophene oligomers were used as photosensitizers in dyads including natural nucleobases as electron acceptors. The charge separation and recombination processes in the dyads were investigated by femtosecond laser flash photolysis, and the driving force dependence of these rate constants was discussed on the basis of the Marcus theory. From this study, the conformation effect on charge recombination process was found. We expect that 3,4-ethylenedioxythiophene oligomers are useful in investigation of excess-electron-transfer dynamics in DNA.

Effect of isomerism and chain length on electronic structure, photophysics, and sensitizer efficiency in quadrupolar (donor)₂-acceptor systems for application in dye-sensitized solar cells

We report on quadrupolar (donor)2-acceptor sensitizers for dye-sensitized solar cells (DSSCs). The acceptor units are based on dithieno[2,3-a:3',2'-c]phenazine and dithieno[3,2-a:2',3'-c]phenazine coupled to thiophene donors. The optoelectronic and photophysical properties of two sets of isomers reveal a rigid structure for linear isomers and an efficient nonradiative decay for branched isomers. These sensitizers were integrated into DSSCs, and the quadrupolar structure is an operational design, as the IPCE reached up to 38% from 400 nm to 600 nm. The lengthening of the donor chain increases the efficiency, demonstrating the appeal of these oligomeric dyes for DSSCs.

Thieno[3,4-b]pyrazine-based oligothiophenes: simple models of donor–acceptor polymeric materials

Thieno[3,4-b]pyrazine-based oligomers have been thoroughly investigated in order to correlate the effects of conjugation length and ‘donor–acceptor’ properties on the resulting optical and electronic properties.

Synthesis and characterization of platinum(II) di-ynes and poly-ynes incorporating ethylenedioxythiophene (EDOT) spacers in the backbone

A series of trimethylsilyl-protected di-alkynes incorporating 3,4-ethylenedioxythiophene (EDOT) linker groups Me(3)Si-C≡C-R-C≡C-SiMe(3) (R = ethylenedioxythiophene-3,4-diyl 1a, 2,2'-bis-3,4-ethylenedioxythiophene-5,5'-diyl 2a, 2,2',5',2''-ter-3,4-ethylenedioxythiophene-5,5''-diyl 3a) and the corresponding terminal di-alkynes, H-C≡C-R-C≡C-H 1b-2b has been synthesized and characterized and the single crystal X-ray structure of 1a has been determined. CuI-catalyzed dehydrohalogenation reaction between trans-[(Ph)(Et(3)P)(2)PtCl] and the terminal di-alkynes 1b-2b in (i)Pr(2)NH/CH(2)Cl(2) (2:1 mole ratio) gives the Pt(II) di-ynes trans-[(Et(3)P)(2)(Ph)Pt-C≡C-R-C≡C-Pt(Ph)(Et(3)P)(2)] 1M-2M while the dehydrohalogenation polycondensation reaction between trans-[((n)Bu(3)P)(2)PtCl(2)] and 1b-2b (1:1 mole ratio) under similar reaction conditions affords the Pt(II) poly-ynes trans-[Pt(P(n)Bu(3))(2)-C≡C-R-C≡C-](n)1P-2P. The di-ynes and poly-ynes have been characterized spectroscopically and, for 1M and 2M, by single-crystal X-ray which confirms the "rigid rod" di-yne backbone. The materials possess excellent thermal stability, are soluble in common organic solvents and readily cast into thin films. Optical absorption spectroscopic measurements reveal that the EDOT spacers create stronger donor-acceptor interactions between the platinum(II) centres and conjugated ligands along the rigid backbone of the organometallic polymers compared to the related non-fused and fused oligothiophene spacers.