Peripheral Substitution of Tetraphenyl Porphyrins: Fine-Tuning Self-Assembly for Enhanced Electroluminescence

This study reports the synthesis of two novel zinc porphyrin families bearing four or eight alkoxy chains at their peripheral phenyl rings, with the length of the alkoxy chains ranging from 2, to 6, and to 12 carbon atoms. All zinc porphyrin derivatives were fully characterized with respect to their photophysical and electrochemical features. The zinc porphyrins could be processed into thin films which, depending on the length of the alkoxy chains on the aryl substituents, were found to be either of an ordered or a disordered nature, as it is revealed by spectroscopic and microscopic techniques. The films containing ordered self-assemblies displayed significantly enhanced electrical conductivity compared to the disordered films. This led to remarkable differences regarding their electroluminescence response that occurs at lower bias. Furthermore, their luminous efficiency was of almost one order of magnitude higher than that of disordered films.