Hydrogen Bond-Regulated Rigid Bis-pyridine-Flanked Thiophene Derivatives for Organic Field-Effect Transistors

We report two model compounds, TTPY and BTPY, which feature resonance-assisted hydrogen bonds (RAHBs) formed between carbamate-functionalized thieno[3,2-b]thiophene or 2,2'-bithiophene cores and flanking pyridine units. Single-crystal structure analysis reveals that moderate RAHBs run along the long axis, whereas weaker noncovalent interactions (e.g., S···O and O···H) are present along the short axis. The synergetic effect of these interactions imparts a rigid, coplanar structure to both TTPY and BTPY. Both computational and experimental studies indicate that RAHBs stabilize the planar molecular conformation through an enthalpic effect, with stabilization energies exceeding 10 kcal mol^-1. The formation of these RAHBs is also entropically favorable, which ensures the stability of the planar conformation at elevated temperatures. Both single crystals adopt a one-dimensional layered stacking mode, and TTPY exhibits closer π-π stacking compared to BTPY. Consequently, TTPY-based organic field-effect transistors (OFETs) show optimal charge transport performance, achieving a maximum hole mobility of 0.035 cm² V^-1 s^-1, which is slightly higher than that of BTPY-based devices (0.026 cm² V^-1 s^-1). Thin film microstructural characterization confirms that TTPY possesses higher crystallinity and greater structural order, accounting for its superior device performance.