Synthesis and Isomeric Effects of Ladder-Type Alkylated Terbenzodithiophene Derivatives

A new class of heptacyclic ladder-type
terbenzodithiophene (TBDT)
structures merging three fused benzodithophenes was developed. Two
TBDT conjugated isomers, named as syn-TBDT and anti-TBDT, where the two thienyl rings in the outmost BDT
units are in the syn- and anti-fashion,
are designed. Two decyl groups are introduced to their 6,13 and 7,14-positions
to form four isomeric 6,13-syn-TBDT, 7,14-syn-TBDT, 6,13-anti-TBDT, and 7,14-anti-TBDT structures which are constructed by the DBU-induced
6-benzannulation involving propargyl-allenyl isomerization of the
dieneyne moieties in the corresponding precursors followed by 6π-electrocyclization/aromatization,
while isomeric TD-syn-TBDT and TD-anti-TBDT with four decyl groups substituted at 6,7,13,14-positions are
synthesized via palladium-catalyzed dialkylacetylene insertion/C–H
arylation of the corresponding iodobiaryl precursors. The intrinsic
properties can be modulated by molecular manipulation of the main-chain
and side-chain isomeric structures. anti-TBDT derivatives
exhibit higher melting points, larger bandgaps, stronger intermolecular
interactions, and higher mobility than the corresponding syn-TBDT analogues. These molecules can be further utilized as building
blocks to make various TBDT-based materials for optoelectronic applications.