Thienoacene‐Fused Pentalenes: Syntheses, Structures, Physical Properties and Applications for Organic Field‐Effect Transistors

Abstract

Three soluble and stable thienoacene-fused pentalene derivatives (1-3) with different π-conjugation lengths were synthesized. X-ray crystallographic analysis and density functional theory (DFT) calculations revealed their unique geometric and electronic structures due to the interaction between the aromatic thienoacene units and antiaromatic pentalene moiety. As a result, they all possess a small energy gap and show amphoteric redox behaviour. Time dependent (TD) DFT calculations were used to explain their unique electronic absorption spectra. These new compounds exhibited good thermal stability and ordered packing in solid state and thus their applications in organic field-effect transistors (OFETs) were also investigated. The highest field-effect hole mobility of 0.016, 0.036 and 0.001 cm(2) V(-1) s(-1) was achieved for solution-processed thin films of 1-3, respectively.

Dithieno[a,e]pentalenes: Highly Antiaromatic Yet Stable π‐Electron Systems without Bulky Substituents

“…Isomeric DTP 3 was also synthesized by Kawase et al [22e] . Since then, the semiconducting properties of organic field‐effect transistors (OFETs) have been intensively studied for several DTP‐containing π‐electron systems, such as conjugated polymers [25] and acene‐like derivatives [5c] . Nevertheless, to our surprise, the effects of the fused thiophene ring on the antiaromaticity of pentalene have yet to be elucidated.…”

Z‐Shaped Pentaleno‐Acene Dimers with High Stability and Small Band Gap

“…For example, we found that the fusion of two five‐membered rings onto the zigzag edges of acene molecules resulted in very stable acenes having a small band gap ( B ) as a result of an intramolecular donor–acceptor interaction, as well as kinetic blocking of the reactive zigzag edges . Alternatively, fusion of an anti‐aromatic pentalene unit along the long axis of an acene ( C ) is another way to approach making stable acene‐based materials for applications such as ambipolar organic field effect transistors (OFETs) –. However, we believe that a more efficient way for stabilization is to fuse the pentalene unit to the zigzag edges of acene molecules because the HOMO coefficients of acenes mainly localize at the zigzag edges, and thus we hypothesized that Z‐shaped pentaleno‐acene dimers ( D ) would be stable and show dramatically different properties from their respective acene monomers.…”

Tuning the antiaromatic character and charge transport of pentalene-based antiaromatic compounds by substitution

“…17–19 Importantly, it has been suggested that antiaromaticity can compress the highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gap and potentially promote carrier mobility in organic semiconductors, which is desirable for application in a number of organic electronic device classes, 20–22 such as organic solar cells (OSCs) 23,24 and organic field-effect transistors (OFETs). 20,25–28 Through important design contributions both from synthetic and theoretical chemists, diverse antiaromatic molecule classes have been developed, including pentalenes, 29,30 indacenes, 31,32 cyclooctatetraenes, 33,34 and their derivatives. 35–37 However, compared to the literature of aromatic compounds, optoelectronic investigations of antiaromatic materials remain far more limited, primarily due to the modest stability of typical antiaromatic compounds 38 and challenges in their chemically modification, which has typically involved fusion with aromatic rings, 19,39 replacement of C–C bonds with isosteric B–N bonds, 40 and aromatic ring functionalization.…”