Properties and degradation of manganese(III) porphyrin thin films formed by high vacuum sublimation
File(s)
Accepted version
Author(s)
Tseng, Hsiang-Han
Serri, Michele
Harrison, Nicholas
Heutz, Sandrine
Type
Journal Article
Abstract
Manganese porphyrins are of interest due to the optical, electronic and magnetic properties of the central metal ion, coupled to the low bandgap of the polyaromatic ring. These attractive characteristics are harnessed in solutions or in ultra-thin films, such as, for example, self-assembled monolayers. However, for devices, thicker films deposited using a controlled and reproducible method are required. Here we present the morphological, structural, chemical and optical properties of manganese(III) tetraphenylporphyrin chloride (MnTPPCl) thin films deposited using organic molecular beam deposition, typically employed to process analogue molecules for applications such as organic photovoltaics. We find, using a combination of UV-vis and X-ray photoelectron spectroscopies, that the sublimation process leads to the scission of the Mn–Cl bond. The resultant film is a Mn(II)TPP:Mn(III)TPPCl blend where approximately half the molecules have been reduced. Following growth, exposure to air oxidizes the Mn(II)TPP molecule. Through quantitative analysis of the time-dependent optical properties, the oxygen diffusion coefficient (D) ∼1.9×10−17cm2/s is obtained, corresponding to a slow bulk oxidation following fast oxidation of a 8-nm-thick surface layer. The bulk diffusion D is lower than for analogous polycrystalline films, suggestion that grain boundaries, rather than molecular packing, are the rate-limiting steps in oxidation of molecular films. Our results highlight that the stability of the axial ligands should be considered when depositing metal porphyrins from the vapor phase, and offer a solvent-free route to obtain reproducible and smooth thin films of complex materials for engineering film functionalities.
Date Issued
2019-11-03
Date Acceptance
2019-10-29
Citation
Journal of Porphyrins and Phthalocyanines, 2019, 23 (11n12), pp.1515-1522
ISSN
1088-4246
Publisher
World Scientific Pub Co Pte Lt
Start Page
1515
End Page
1522
Journal / Book Title
Journal of Porphyrins and Phthalocyanines
Volume
23
Issue
11n12
Copyright Statement
© 2019 World Scientific Publishing. Electronic version of an article published as Online View https://doi.org/10.1142/S1088424619501700
Environmental Health Perspectives (EHP) is an open-access publisher. All original content published in the journal is in the public domain and may be accessed and read freely by all interested users.
Environmental Health Perspectives (EHP) is an open-access publisher. All original content published in the journal is in the public domain and may be accessed and read freely by all interested users.
Identifier
https://www.worldscientific.com/doi/abs/10.1142/S1088424619501700
Subjects
Science & Technology
Physical Sciences
Chemistry, Multidisciplinary
Chemistry
manganese tetraphenylporphyrin
thin film
OMBD
sublimation
axial ligand
oxygen diffusion
oxidation
RAY PHOTOELECTRON-SPECTROSCOPY
MOLECULAR-OXYGEN
SPECTRA
0305 Organic Chemistry
Organic Chemistry
Publication Status
Published
Date Publish Online
2019-11-03