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

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.