Electron transport thiophene-5,5-dioxides

Thiophene-S,S-Dioxides as Emissive and Electron Transport Moieties... 

Poly- and oligothiophenes are generally p-type (hole-transporting) semiconductors. In thiophene-S,S-dioxide (98AM551 98JOC5497), this modification results in de-aromatization of the thiophene unit and increases the electron affinity and electron-transport properties of the... 

In contrast to thiophene-5,5 -dioxide, the non-aromatic character of which limits the stability of the derived materials, the aromatic dibenzothiophene-5,5 -dioxide is very stable and topologically equivalent to a fluorene moiety. Its LUMO energy level is 1 eV Iowct than that in fluorene [168], and several highly fluorescent molecular and oligomeric materials based on dibenzothiophene-5, 5 -dioxide have been synthesized and studied (125 and 126). Diphenylamino end-capped dibenzothiophene-5,5-dioxide derivatives 125a-c were used as emitters [73a, 169, 170], the dibenzothiophene-5,5-dioxide-quinoxaline derivative 126 was used as an electron-transporting material [171], and multilayer OLEDs based on these compounds demonstrated excellent performance (Table 19.5). 

Oxidation of tetramethylorthothiophenophanes with m-CPBA gave a mixture of thiophene 1,1-dioxides 55 and 56 in a ratio depending on the amount of m-CPBA used (Scheme 55) [65], The thiophene 1,1-dioxide 57 could also be easily obtained using this oxidant (Scheme 56) [66], Application of this method produced novel photochromic compounds 58-60, having relatively high fluorescence efficiencies (Scheme 57) [67], as well as the precursors 61-63 for electron-transporting materials (Scheme 58) [68],... 

Single-layer EL devices possess excellent performances, comparable to those of multilayered devices. Compared with other thiophene-S, S -dioxide and benzothiophene-5, 5 -dioxide derivatives, compounds 12 and 13 have a better balance of electron- and hole-transport properties which are probably at the origin of the good EL performances in single-layered devices. 

---