Masamatsu Hoshino

Ultraviolet photoemission study of oligothiophenes: π-band evolution and geometries

Ultraviolet photoelectron spectroscopy (UPS) has been applied to the investigation of the electronic structure of oligothiophenes with 4–8 thiophene rings. In a series of α‐linked oligomers (αn with n being the number of rings), a systematic evolution of the π band is observed. Several peaks which correspond to the π band are observed in the region of 0.7–3 eV below the Fermi level (EF), and the bandwidth becomes broader with increasing n. The nonbonding π band is observed at 3.5 eV below EF and its energy is almost independent of the number of thiophene units. UPS spectra of α7 and α8 are fairly similar to the spectra of polythiophene, showing that these oligomers are good model compounds of the polymer. The ionization threshold energy of α7 and polythiophene was observed to be 5.3 eV. The effect of irregularity on the π‐electron system was also studied by using oligomers which contain a β linkage or a vinylene group at the middle of the molecule. The UPS spectra showed that the β linkages significantly ...

Langmuir-Blodgett films of oligo- and polythiophenes with well-defined structure

Abstract Using terthiophene and its derivatives, quater-, quinque-, sexi-, and α- or β-septithiophenes, Langmuir-Blodgett (LB) films including oligo- or polythiophenes with well-defined alignments have been obtained. Esters of terthiophene with a short alkyl chain form stable condensed monolayers on water and can be deposited by the LB method. α-polythiophenes without any hydrophilic groups can be incorporated in LB films of mixed monolayers with arachidic acid. In these monolayer assemblies, the long axes of oligo- or polythiophenes stand nearly vertically. LB films of the terthiophene ester derivatives showed a large dielectric constant and a high conductivity which were enhanced by iodine doping.

Synthesis and properties of 1,8-Di(2-thienyl)-, 1,8-bis(5,2′-bithiophene-2-yl)-, 1,8-bis(5,2′:5′,2″-terthiophene-2-yl)-, and 1,8-bis(5,2′:5′,2″:5″,2″′-quaterthiophene-2-yl)naphthalenes and related compounds

Abstract 1,8-Di(2-thienyl)-, 1,8-bis(5,2′-bithiophene-2-yl)-, 1,8-bis(5,2′:5′,2″-terthiophene-2-yl)-, and 1,8-bis-(5,2′:5′,2″:5″,2″′-quaterthiophene-2-yl)naphthalenes (1a, 1b, 1c and 1d, respectively) were synthesized starting from 1,8-dibromonaphthalene by appliction of NiCl2(dppp)-catalyzed coupling of aryl bromides with thienylmagnesium bromides. For comparison with these compounds, 1-(2-thienyl)-, 1-(5,2′-bithiophene-2-yl)-, 1-(5,2′:5′,2″-terthiophene-2-yl)-, and 1-(5,2′:5′,2″:5″,2″′-quaterthiophene-2-yl)naphthalenes (2a–d) were also prepared. Inspection of 1H and 13C NMR and UV/Vis data of 1a–d and 2a–d including X-ray single crystal structure data of 1b suggests that the planes of two oligothiophene units of 1a–d are approximately parallel to each other and are at large angles to the naphthalene ring. In accordance with these findings, CV oxidation potential data show that the radical cations formed from 1a–d are stabilized by intramolecular electron transfer interaction of the two oligothiophene units.

Synthesis and reactions of 3,4-di-t-butylthiophene

Abstract 3,4-Di-t-butylthiophene (1) was surprisingly easily synthesized from readily accessible bis(2-t-butyl-2-oxoethyl) sulfide (2). Reactions of 1 with a variety of electrophiles were examined.

General synthesis of 2,5-dihydrothiophenes (3-thiolenes) from diketo sulfides

Abstract The intramolecular reductive coupling reaction of easily accessible diketo sulfides by a low-valent titanium reagent [prepared from titanium(IV) chloride and zinc powder] provides an efficient general synthesis of 2,5-dihydrothiophenes.

A One-Pot synthesis of Substituted Thieno[3,2-b]thiophenens and Selenolo[3,2-b]selenophenes

Heating a mixture of 2,5-dimethyl-3-hexyne-2,5-diol (3a) with elemental sulfur in benzene at 190-200 °C in an autoclave affords 3,6-dimethyl- thieno[3,2-b]thiophene (5a) in 26% yield. The reaction provides a practical one-pot synthesis of several gram quantifies of (5a), even if the yield is moderate, since (3a) is commercially available and inexpensive. The reaction proceeds via 2,5-dimethyl-1,5-hexadiene-3-yne (4a) as one of probable intermediates, which is produced by dehydration of (3a). Addition of p-toluenesulfonic acid promotes the dehydration of (3a) and thus can lower the reaction temperature. In addition, the reaction of 4a, prepared from (3a) independently, with sulfur affords (5a) in a somewhat improved yield (33%). The reaction of (3a) with elemental selenium also provides a one-pot synthesis of 3,6-dimethyl- selenolo[3,2-b]selenophene (9a) in 16% yield. Reactions of some other acetylenic diols with elemental sulfur and selenium are also described

Generation and dienophilic reactivity of α-oxoselenoaldehydes and ketones

Abstract The reaction of elemental selenium with sulfur ylides stabilized by electron-withdrawing substituent(s) affords a facile method for generation of functionalized selenocarbonyl compounds, which can be effectively trapped by Diels-Alder reaction with 1,3-dienes.

General synthesis of polysubstituted thiophenes from diketo sulfides

Treatment of diketo sulfides with a low-valent titanium reagent at 0 °C (in two cases at room temperature) affords 3,4-dihydroxythiolanes in good yields. The acid-catalyzed (p-toluenesulfonic acid) dehydration of the latter compounds leads to the corresponding thiophenes in excellent yields.

A convenient synthesis of 1,2-dithietes and α-dithiocarbonyl compounds by sulfuration of acetylenic compounds

Di-tert-butyl-, di-1-adamantyl-, 1-(1-adamantyl)-2-tert-butyl-, and 1-(1-adamantyl)-2-phenylacetylenes react with elemental sulfur to afford th

A novel synthesis of selenophenes

Abstract Reduction of α,α′-diketo selenides with a low-valent titanium reagent usually affords 3,4-dihydroxyselenolanes, from which the corresponding selenophenes are obtained by acid-catalyzed dehydration. A surprising exception is the formation of 2,4-dihydroxy- 2,4-di- t -butylselenolane from bis(2- t -butyl-2-oxoethyl) selenide, the former being converted to 2,4-di- t -butylselenophene by acid treatment.