Conformational properties of 3,3′-,3,4′- and 4,4′-dimethyl- and -bis(methylsulfanyl)-2,2′-bithiophenes

Crystal structure of head-to-head and tail-to-tail β,β′-dibromo-substituted bithiophenes as model compounds for poly(3-bromothiophene)

“…The dimensions of the thiophene ring, whose atoms are coplanar to within l 0.001 Å , compare well with those reported for the 5,59-dibromo analogue [14], and with those observed in a number of symmetrically-substituted derivatives such as the 4,49-dimethyl- [18], 4,49-dimethylthio- [19], 3,39-and 4,49-dimethoxy- [13,16] and 3,39-and 4,49 dipentoxy-2,29-bithiophene [17]. It seems that the conjugation between thienyl ring atoms is unaffected by the electron-withdrawing ability of the Br substituents.…”

Synthesis and Characterization of Bis[1]benzothieno[3,2-b:2′,3′-d]pyrroles: Quantitative Effects of Benzannulation on Dithieno[3,2-b:2′,3′-d]pyrroles

“…1.41 vs. 1.42 Å). This bond is also shorter than the interannular bonds of either 2,2′-bithiophene (1.45 Å) [ 44 ] or 4 (1.458 Å), implying strong coupling through the central pyrrole ring.…”

Thermal Characterization of Sexithiophenes Regioselectively Functionalized with Electron Donor Methylsulfanyl Groups

“…Indeed, according to theoretical calculations, thiophene dyads and triads with head-to-tail junctions are characterized by greater conformational disorder and smaller inter-ring twist angles than those containing head-to-head junctions. [18,19] On the contrary, the presence of head-to-head linkages implies a more restricted number of conformations and greater inter-ring twist angles. This implies a less effective conjugation length and a consequent hypsocromic effect on the UV absorption band of the system.…”