Spectral properties, electronic states, and aggregation of highly-fluorinated zinc phthalocyanines

Fluoroalkyl zinc phthalocyanines (F[Formula: see text]PcZn) are an emerging class of functional tetrapyrroles with fluoro and perfluoroalkyl groups decorating the periphery of the macrocycle. F[Formula: see text]PcZn complexes, 16 [Formula: see text] n [Formula: see text] 64, exhibit strong absorptivity in the red region of the visible spectrum. Analysis of absorption, emission, and, most importantly, magnetic circular dichroism spectra, coupled with detailed molecular orbital calculations using time-dependent density functional theory, was used to probe the differential effects of increasing the number of peripheral fluoro groups. The impact of the electronegativity imparted by the fluorine atoms and iso fluoroalkyl groups, as well as the resulting increased steric crowding, was considered in terms of the electronic properties of a range of porphyrins and phthalocyanines. The contribution of F[Formula: see text]PcZn aggregation to the electronic spectra in solution was elucidated by analyzing TD-DFT-calculated spectra and comparing them with the X-ray structure of the solid state.