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Optical and morphological properties of ultra‐thin H 2 TPP, H 4 TPP and ZnTPP films
Author(s) -
Bussetti Gianlorenzo,
Campione Marcello,
Sassella Adele,
Duò Lamberto
Publication year - 2015
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201350260
Subject(s) - porphyrin , tautomer , isotropy , anisotropy , spectral line , molecule , materials science , thin film , spectroscopy , base (topology) , free base , analytical chemistry (journal) , chemistry , photochemistry , optics , nanotechnology , stereochemistry , organic chemistry , physics , mathematical analysis , mathematics , salt (chemistry) , quantum mechanics , astronomy
An interesting and well known chemical reaction (tautomerism) in free‐base porphyrins (namely H 2 TPP) has been considered promising for application in organic electronics. Recently, we have proposed an original strategy to obtain a pure 2D layer of H 2 TPP molecules, where tautomers are aligned along the same direction, inducing anisotropy in the porphyrin optical transitions. This opens the route to an organic optical device if the tautomer signal can be inhibited and restored in a controlled mode. Here, we demonstrate that, conversely to H 2 TPP film, the di‐acid H 4 TPP sample, easily reachable from free‐base porphyrins, shows almost isotropic transitions. The change of the optical spectral intensities between H 2 TPP and H 4 TPP samples, as detected by reflectance anisotropy spectroscopy (RAS), is interpreted in terms of two distinct logic states. Furthermore, RAS spectra acquired both on the H 2 TPP and the H 4 TPP samples are compared with the optical spectra of ultra‐thin films of ZnTPP, the latter being a genuine isotropic porphyrin.