Electronic properties of the charge transfer material MnPc/F4TCNQ

Abstract

We present electronic properties of a charge transfer material consisting of Manganese(ii)Phthalocyanine (MnPc) and 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), investigated by means of photoemission spectroscopy and electron energy-loss spectroscopy, as well as supporting density functional theory calculations. We report the successful formation of a bulk material characterized by a strong interaction of the molecular compounds which affects the optical properties significantly. Our investigations reveal a significant charge transfer, whereas the MnPc molecule is oxidized and F4TCNQ is reduced. The valence band data indicate a full charge transfer between the two partners. The electronic excitation spectrum reveals a relatively small energy gap of MnPc/F4TCNQ of about 0.7 eV, which is related to a charge transfer excitation.

Charge Transfer at the Interface Between MnPc and F6TCNNQ

“…The appearance of this structure at lower binding energy is consistent with the expected chemical shift for reduced/negatively charged F 6 TCNNQ − . Moreover, the fact that we do not consider an extra C 1s contribution for oxidized MnPc at the interface is fully consistent with previous data on the MnPc/F 4 TCNQ charge transfer material where the C 1s emission of MnPc and MnPc + appeared at the same energy …”

“…The data in Figure demonstrate a clear change in line shape and energy position of the Mn 2p 3/2 core level feature. Equivalent changes of the Mn 2p 3/2 core level feature have been observed in the past at interfaces and in bulk structures, where a charge transfer resulted in the removal of an electron from MnPc, i.e., an oxidation . Thus, our data clearly evidence that there is charge transfer at the MnPc/F 6 TCNNQ interface and that the Mn central atom in MnPc is oxidized.…”

“…For instance, MnPc shows by a small ionization potential of 4.5 eV, a large electron affinity and a small band gap . MnPc also behaves differently as compared to other transition metal phthalocyanines in view of charge transfer at interfaces or in bulk systems . Recently, F 6 TCNNQ has been applied in organic devices with particular advantages such as a very high electron affinity of 5.5 eV and a relatively large molecular mass, which prevents diffusion of the molecule in thin films.…”

Electron Transfer and Unusual Chemical Transformations of F4‐TCNQ in a Reaction with Mn‐Phthalocyanine

“…The first step to grow bicomponent crystals was naturally performed in the moisture‐free conditions that are most consistent with those used for the preparation of thin films . However, no single crystals suitable for single‐crystal X‐ray diffraction study could be grown from dry solvents.…”

“…Recently, it was shown by one of us that strong charge‐transfer (CT) interactions are observed in thin films consisting of manganese(II) phthalocyanine (MnPc) and 2,3,5,6‐tetrafluoro‐7,7,8,8‐tetracyanoquinodimethane (F4‐TCNQ), resulting in 1 e transfer with oxidation of the Mn ion and the reduction of the F4‐TCNQ. To study this CT system in more detail, we have tried to grow binary single crystals using physical vapor transport, which was earlier successfully applied to combinations involving polyaromatic hydrocarbons and TCNQ derivatives .…”