Efficient Intramolecular Charge Transfer in Oligoyne‐Linked Donor–π–Acceptor Molecules

Abstract

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Oligo(p‐phenyleneethynylene) (OPE) Molecular Wires: Synthesis and Length Dependence of Photoinduced Charge Transfer in OPEs with Triarylamine and Diaryloxadiazole End Groups

“…The oxidation potential of 0.46 V for 1, assigned to the one-electron oxidation of the triarylamine unit, decreases to 0.40-0.42 V for the longer molecules 2-5 ( Figure 1). [29,30] The symmetrical D--D compound 6 contains two oxidation waves only 120 mV apart, corresponding to sequential oxidations at the two (electronically interacting) triarylamine units. [31] Additional oxidation waves ascribed to the bridge unit are also observed at higher potentials (0.65-0.88 V) which shift cathodically from 2 to 5.…”

Regiospecific Formation and Unusual Optical Properties of 2,5‐Bis(arylethynyl)rhodacyclopentadienes: A New Class of Luminescent Organometallics

“…We attribute the negligible influence of these ligands on the photophysical properties of the compounds to the fact that the aryl rings are significantly rotated out of co-planarity with the metallacycle (see Table 2) and, thus, conjugation between the rhodium atom and the substituent on the acetylide ligands is not increased. For this reason, rhodacyclopentadiene 3 c with ÀCCÀCCÀ(p-C 6 H 4 À NPh 2 ) [24] as a ligand was synthesized, in which the two alkynyl groups were initially anticipated to ensure co-planarity of the aryl rings. However, despite the additional alkyne unit, the absorption and emission spectra of 3 c are similar to 3 a/b and 3 d. A molecular modeling study showed that steric hindrance between the p-phenylene ortho-hydrogen atoms of the ÀC CÀCCÀ(p-C 6 H 4 ÀNPh 2 ) ligand and the adjacent aryl ring on the diethynylmetallacycle again prevents the desired co-planarity.…”

Solvent Dependence of the Single Molecule Conductance of Oligoyne-Based Molecular Wires

“…9 Nevertheless, this structural flexibility does not detract from the impressive electronic properties of oligoynes, which offer considerable interest for their electronic, opto-electronic and electrical charge transport properties. 10 Despite their apparent chemical simplicity it is a challenge to synthesize long carbon chains due to potential instability of R-(C≡C) x -H intermediates and also instability of the longer oligoyne products for certain, particularly small, R groups. This issue was circumvented by Bohlmann who introduced bulky tertiary butyl ( t Bu) end groups in an n = 7 oligomer ( t Bu-(C≡C) 7 -t Bu), 11 and then also by Johnson and Walton, who extended the chain to t Bu-(C≡C) 12 -t Bu.…”