Charge injected proton transfer in indigo derivatives

In analogy with excited-state proton transfer, proton transfer is significantly facilitated in cationic and anionic molecules of indigo derivatives generated in field-effect transistors. We have prepared extended and truncated indigo derivatives and investigated their ambipolar transistor properties. Since the proton transfer reduces the energy gap from 2.2 to 0.4 eV, the proton transferred states are stabilized in the charge injected cationic and anionic states; the energy increase is as small as 0.5 eV, which is half of that in the neutral state. The intermolecular proton transfer enlarges the equilibrium N-H distance typically by 0.03 Å, and improves the donor and acceptor abilities by 0.2-0.4 eV, though the reorganization energy is practically unchanged. In addition, the transfer integrals along the hydrogen bonds are as large as one third of the columnar transfers, to facilitate the two-dimensional carrier conduction. The influence of proton transfer is most significant in indigo and truncated indigo derivatives, though isoindigo and quinacridone exhibit similar properties. Accordingly, indigo derivatives show much better donor and acceptor abilities than those expected from isolated molecules.

Diselenolene proligands: reactivity and comparison with their dithiolene congeners

Selenophene and diselenine were synthesized from diselenolene proligands.

Transistor Characteristics of Charge-Transfer Complexes Observed across a Neutral-Ionic Transition

For basic understanding of transistor properties of doped organic semiconductors, 3,3',5,5'-tetramethylbenzidine charge-transfer complexes are investigated, which change from neutral to ionic by varying the acceptors. When going into the ionic state, the bulk conduction increases more rapidly than the mobility, but sufficiently thin devices exhibit transistor properties. The resulting ambipolar characteristics are analyzed in the linear regions at small drain voltages in analogy with graphene transistors. The model is further extended to include partial overlap of electron and hole transport regions. In the temperature dependence, the activation energy loses gate voltage dependence when the neutral-ionic transition takes place by 0.1-0.2 eV above the equal acceptor and donor levels; the difference comes from the typical trap (polaron) depth or the Madelung energy.

Structures and transistor properties of extended and unsymmetrical birhodanines

Extended and unsymmetrical birhodanines, including phenyl and unsubstituted parts, are prepared and show characteristic molecular packing and n-channel transistor properties.