Electronic Structure of Metal-Free Porphyrazines in Thin Films

Abstract

We report photoemission spectra of the valence region for a series of linearly benzo-annelated porphyrazine molecules in thin films. This family of compounds, with stepwise varied ligand size, is an ideal model system to investigate the evolution of the electronic structure with the increasing π-electron system of the molecule. Specifically, the electronic structure of tert-butyl-substituted metal-free tetraazaporphyrin, phthalocyanine, and naphthalocyanine is investigated by photoelectron spectroscopy using synchrotron radiation in the 70−105 eV photon energy range. A shift of the highest occupied molecular orbital toward lower binding energies as a function of the increasing ligand size is found and discussed on the basis of existing theoretical calculation. Only a small influence of the tert-butyl substituent group on the photoemission spectra is observed as compared to spectra of unsubstituted molecules.

Effect of Thickness on Structural and Optical Properties of Tetra‐tert‐ butyl‐2, 3‐naphthalocyanine Thin Films

“…Several free based naphthalocyanine derivatives exhibit a strong O-O absorption band region in the region 800 nm matching the wavelength of most semiconductor diode lasers and Ti-Sapphire lasers. Most studies related to phthalocyanine derivatives are addressed to the structural aspects of the molecular arrangement in thin films and in solution phase using UPS, XPS or NEXAFS [5][6][7][8] .…”

Strong correlation effects in the electron binding energies of phthalocyanine

“…Extended conjugated systems of π electrons not only provide for intense coloring but also make these compounds promising candidates for various electronic devices 3, 4 and solar cell components 5, 6. These macrocycles provide a variety of substitution sites that can be used to create compounds with controlled electron donor/acceptor properties 7, 8.…”

“…To our knowledge, no works on gas‐phase PES of substituted, metal‐free phthalocyanines have been published. PES of tetra‐( t ‐butyl)‐substituted phthalocyanine thin films were obtained in synchrotron experiments with photon energies between 20 and 180 eV 7. Alkyl substitutions have little effect on the first peak's position.…”

Absorption, luminescence, and Raman spectroscopic properties of thin films of benzo-annelated metal-free porphyrazines

“…This makes a detailed understanding of the thin film properties highly desirable. Most studies so far have addressed the structural aspects of the molecular arrangement of phthalocyanines in the condensed thin film phase using UPS, XPS or NEXAFS [10][11][12][13]. Valuable additional information in particular concerning the optical properties can be gained from luminescence spectroscopy.…”