organic semiconductors containing multi-heteroatom rings
abstract
oligomers of thiophene are ubiquitous in molecular materials research. other ring systems,
especially those lacking at least c2v symmetry are much less common. we investigated
thiophene-thiazole, pyrrole-thiazole, thiophene-furan, and thiophene-selenophene co-oligomers,
which nominally have the same conjugation length and physical dimensions as thiophene
oligomers but contain a heteroatom, that should impact the electronic properties. the lower
symmetry of the 1,3-thiazole system, among other attributes, makes these new systems
chemically challenging to synthesize; however, the electronic and steric variability makes them
interesting targets. one common method of synthesizing thiazole is the ring-closing reaction that
generates an amino-substituted thiazole. we have done a systematic study to convert the
aminothiazole to a more useful synthon using sandmeyer conditions. we herein present the
synthesis, characterization, and molecular or photoelectronic structures of selected mixed
oligomer systems, along with a computational study to measure bond length alternation,
localization indices, and homo-lumo (band gap) energy. aminothiazole can be deaminated
using sandmeyer conditions. as conjugation length increases with the addition of a more
electron withdrawing group, there is a general decrease of the band gap as well as of the homo-
lumo energies.