Synthesis, spectroscopic and DFT characterization of 4β-(4-tert-Butylphenoxy)phthalocyanine Positional Isomers for Non-linear Optical Absorption

Abstract

In this work the synthesis, spectral characterization and non-linear optical properties of metal-free 4β-(4-tert-butyl-phenoxy)phthalocyanine isomers are described and compared to the previously reported alpha derivative. The second-order nonlinear optical properties of the phthalocyanine isomers were investigated using the Z-scan technique and compared to the theoretical data obtained from density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations. Z-scan results indicated strong non-linear behaviour, revealing reverse saturable absorption (RSA) profiles for all four isomers. The experimental βexp values showed the following trend: C4h (9.31×10-10 mMW-1)>D2h (7.89×10-10 mMW-1)>Cs (7.32× 10-10 mMW-1) > C2v (1.77 × 10-10 mMW-1). These results were similar to that obtained with the 4á-(4-tert-butylphenoxy)phthalo-cyanines as the C2v and Cs isomers were found to have the lowest βexp values compared to other symmetries. The 4β-(4-tert-butylphenoxy)phthalocyanine C4h isomer was found to show betternon-linearoptical properties compared to all other isomers.