Semiconducting Organic Assemblies Prepared from Tetraphenylethylene Tetracarboxylic Acid and Bis(pyridine)s via Charge-Assisted Hydrogen Bonding

Principles of crystal engineering have been applied toward the construction of supramolecular assemblies between an acid-functionalized tetraphenylethylene derivative and three different bis(pyridine)s [4,4'-bis(pyridyl)ethylene, 4,4'-bis(pyridyl)ethane, and 4,4'-bipyridine]. Each assembly was structurally characterized, and charge transfer interactions within each sample were visually apparent. Quantum chemical calculations were used to determine crystal band structure and band gap magnitude, and electrical properties of the materials were measured using conducting probe atomic force microscopy (CP-AFM). The crystals displayed charge-carrier capability, and the magnitude of semiconductivity varied systematically as a function of conjugation in the bis(pyridine) component. Crystals incorporating 4,4'-bis(pyridyl)ethylene and 4,4'-bipyridine displayed conductivities comparable to those of established organic semiconductors (μ(eff) = 0.38 and 1.7 × 10(-2) cm(2)/V·s, respectively).