6533b86dfe1ef96bd12ca031

RESEARCH PRODUCT

Tuning the Electronic Properties of Nonplanar exTTF-Based Push–Pull Chromophores by Aryl Substitution

subject

description

International audience; A new family ofπ-extended tetrathiafulvalene (exTTF) donor−acceptorchromophores has been synthesized by [2 + 2] cycloaddition of TCNE with exTTF-substituted alkynes and subsequent cycloreversion. X-ray data and theoretical calculations,performed at the B3LYP/6-31G**level, show that the new chromophores exhibit highlydistorted nonplanar molecular structures with largely twisted 1,1,4,4-tetracyanobuta-1,3-diene (TCBD) units. The electronic and optical properties, investigated by UV/visspectroscopy and electrochemical measurements, are significantly modified when theTCBD acceptor unit is substituted with a donor phenyl group, which increases the twistingof the TCBD units and reduces the conjugation between the two dicyanovinyl subunits.The introduction of phenyl substituents hampers the oxidation and reduction processesand, at the same time, largely increases the optical band gap. An effective electroniccommunication between the donor and acceptor units, although limited by the distortedmolecular geometry, is evidenced both in the ground and in the excited electronic states.The electronic absorption spectra are characterized by low-to medium-intense charge-transfer bands that extend to the near-infrared.