Synthesis and Spectral Properties of a Highly Soluble Push−Pull Type of Quinoidal Thiophenes

A series of push−pull quinoidal thiophenes 5a,b and 6a−c substituted with an electron-donating 1,3-dithiol-2-ylidene unit and an electron-withdrawing dicyanomethylene unit at the terminals is developed. They are highly soluble in common solvents and deeply colored with extension of the thienoquinoid skeleton

Novel Selenocycle-Fused TTF-Type of Electron Donors Forming Conducting Molecular Complexes: Bis(ethyleneseleno)tetrathiafulvalene (BES-TTF), Diselenolotetrathiafulvalene (DS-TTF), and Bis(ethyleneseleno)tetraselenafulvalene (BES-TSF)

The title selenocycle-fused tetrathiafulvalene derivatives (BES-TTF and DS-TTF) and tetraselenafulvalene derivative (BES-TSF) have been synthesized as novel electron donors, and their conducting molecular complexes have been studied. Although DS-TTF formed only semiconducting complexes, BES-TTF and BES-TSF gave metallic complexes with various electron acceptors, such as TCNQ, ClO4-, PF6-, and AsF6-. Among them, the TCNQ complex of BES-TSF showed an extraordinarily high room-temperature conductivity of 2700 ± 500 S cm-1, which is of the highest class for a molecular complex. The complexes of BES-TTF underwent a typical metal-to-insulator transition at low temperature, characteristic of one-dimensional organic metals. On the other hand, complexes of BES-TSF were less temperature-dependent and remained highly conducting, even down to cryogenic temperature. The different behaviors of the three donors are discussed on the basis of the crystal structures of their representative complexes as elucidated by X-ray crystallographic analyses

One-Pot Synthesis of Heterocycle-Fused 1,3-Diselenole-2-selones as the Key Precursors of Tetraselenafulvalene-Type Electron Donors

A simple one-pot synthetic method of a series of 4,5-alkylenedichalcogeno-substituted 1,3-diselenole-2-selones by successive treatments of trimethylsilylacetylene with butyllithium, selenium, carbon diselenide, and finally α,ω-bis(chalcogenocyanato)alkanes is described

2,6-Diarylnaphtho[1,8-<i>bc</i>:5,4-<i>b</i><i>‘</i><i>c</i><i>‘</i>]dithiophenes as New High-Performance Semiconductors for Organic Field-Effect Transistors

A series of 2,6-diaryl-substituted naphtho[1,8-bc:5,4-b‘c‘]dithiophene derivatives 2−6, whose aryl groups include 5-hexyl-2-thienyl, 2,2‘-bithiophen-5-yl, phenyl, 2-naphthyl, and 4-biphenylyl, was synthesized by the palladium-catalyzed Suzuki−Miyaura coupling and utilized as active layers of organic field-effect transistors (OFETs). All devices fabricated using vapor-deposited thin films of these compounds showed typical p-type FET characteristics. The mobilities are relatively good and widely range from 10-4 to 10-1 cm2 V-1 s-1, depending on the substituent groups. Among them, the mobilities of the devices using films of 3−5 tend to increase with the increasing temperature of the Si/SiO2 substrate during film deposition. In particular, the device based on the naphthyl derivative 5, when fabricated at 140 °C, marked a high mobility of 0.11 cm2 V-1 s-1 with an on/off ratio of 105, which is a top class of performance among organic thin-film transistors. Studies of X-ray diffractograms (XRDs) have revealed that the film of 4 and 5 is composed of two kinds of crystal grains with different phases, so-called “single-crystal phase” and “thin film phase”, and that the proportion of the thin film phase increases with an increase of the substrate temperature. In the thin film phase the assembled molecules stand nearly upright on the substrate in such a way as to be favorable to carrier migration

2,6-Diarylnaphtho[1,8-<i>bc</i>:5,4-<i>b</i><i>‘</i><i>c</i><i>‘</i>]dithiophenes as New High-Performance Semiconductors for Organic Field-Effect Transistors

A series of 2,6-diaryl-substituted naphtho[1,8-bc:5,4-b‘c‘]dithiophene derivatives 2−6, whose aryl groups include 5-hexyl-2-thienyl, 2,2‘-bithiophen-5-yl, phenyl, 2-naphthyl, and 4-biphenylyl, was synthesized by the palladium-catalyzed Suzuki−Miyaura coupling and utilized as active layers of organic field-effect transistors (OFETs). All devices fabricated using vapor-deposited thin films of these compounds showed typical p-type FET characteristics. The mobilities are relatively good and widely range from 10-4 to 10-1 cm2 V-1 s-1, depending on the substituent groups. Among them, the mobilities of the devices using films of 3−5 tend to increase with the increasing temperature of the Si/SiO2 substrate during film deposition. In particular, the device based on the naphthyl derivative 5, when fabricated at 140 °C, marked a high mobility of 0.11 cm2 V-1 s-1 with an on/off ratio of 105, which is a top class of performance among organic thin-film transistors. Studies of X-ray diffractograms (XRDs) have revealed that the film of 4 and 5 is composed of two kinds of crystal grains with different phases, so-called “single-crystal phase” and “thin film phase”, and that the proportion of the thin film phase increases with an increase of the substrate temperature. In the thin film phase the assembled molecules stand nearly upright on the substrate in such a way as to be favorable to carrier migration

Synthesis and Properties of the Longest Oligothiophenes: The Icosamer and Heptacosamer

Synthesis and Properties of the Longest Oligothiophenes:  The Icosamer and Heptacosame

Synthesis and Spectral Properties of a Highly Soluble Push−Pull Type of Quinoidal Thiophenes

A series of push−pull quinoidal thiophenes 5a,b and 6a−c substituted with an electron-donating 1,3-dithiol-2-ylidene unit and an electron-withdrawing dicyanomethylene unit at the terminals is developed. They are highly soluble in common solvents and deeply colored with extension of the thienoquinoid skeleton

A General Method for the Synthesis of Alkylenedithio- and Bis(alkylenedithio)tetraselenafulvalenes

A general synthetic method toward a series of alkylenedithio- and bis(alkylenedithio)tetraselenafulvalenes, i.e., methylenedithio- (MDT-TSF, 1a), ethylenedithio- (EDT-TSF, 1b), propylenedithio- (PDT-TSF, 1c), bis(methylenedithio)- (BMDT-TSF, 2a), bis(ethylenedithio)- (BETS, 2b), and bis(propylenedithio)tetraselenafulvalene (BPDT-TSF, 2c), as superior electron donors for organic conductors has been developed. This method is advantageous to ready access to a series of compounds from common synthetic intermediates, 2-methylthio-3-(2-methoxycarbonylethylthio)-tetraselenafulvalene (6) and 2,6(7‘)-bis(methylthio)-3,7(6‘)-bis(2-methoxycarbonylethylthio)tetraselenafulvalene (7), for the asymmetrical alkylenedithio- and symmetrical bis(alkylenedithio)-TSFs, respectively. These key intermediates are readily prepared by phosphite-promoted coupling reactions of 4-methylthio-5-(2-methoxycarbonylethylthio)-1,3-selenole-2-selone (5) or by a reaction of TSF with LDA and methyl 3-thiocyanatopropionate. The latter method provides not only the successful conversion of TSF to these heterocycle derivatives but also a generally acceptable route to them, since TSF is accessible without the toxic and less easily available CSe2

Fluorescence Up-Conversion Study of Excitation Energy Transport Dynamics in Oligothiophene−Fullerene Linked Dyads

Photoinduced excitation energy transport dynamics in oligothiophene−fullerene linked dyads, nT-C60 (n = 4, 8, and 12), have been investigated by femtosecond fluorescence up-conversion. In 8T-C60 and 12T-C60, each time profile of the fluorescence due to the 1nT* moiety consists of two components. The sub-picosecond component and a few picosecond components were experimentally evaluated depending on the lengths of oligothiophenes (n =8 and 12) and on the analyzing wavelength of the fluorescence. However, the time trace of the fluorescence due to 14T*-C60 decayed with a single short component in ∼300 fs due to direct excited energy transfer (EET) from the 14T* moiety to the C60 moiety. On the basis of the kinetic models considering the short and long locally π-conjugative thiophene segments in 8T-C60 and 12T-C60, the rate parameters of the elemental processes were evaluated. Sub-picosecond time constants of nT-C60 were found to be EET from the thiophene segment vicinal to the C60 moiety and intrachain energy transfer. Slower picosecond dynamics mainly corresponds to EET from the thiophene segments apart from the C60 moiety

2,6-Diphenylbenzo[1,2-<i>b</i>:4,5-<i>b</i>‘]dichalcogenophenes: A New Class of High-Performance Semiconductors for Organic Field-Effect Transistors

2,6-Diphenylbenzo[1,2-b:4,5-b‘]dichalcogenophenes including thiophene, selenophene, and tellurophene analogues as organic semiconductors for field-effect transistors were effectively synthesized in three steps from commercially available 1,4-dibromobenzene. All three benzodichalcogenophenes acted as good p-type semiconductors, and particularly the selenophene analogue, 2,6-diphenylbenzo[1,2-b:4,5-b‘]diselenophene, showed high FET mobility of 0.17 cm2 V-1 s-1