Synthesis, spectroscopic and DFT Characterization of 4β-(4-tert-Butylphenoxy)phthalocyanine positional isomers for non-linear optical absorption

In this work the synthesis, spectral characterization and non-linear optical properties of metal-free 4 β -(4 -tert -butylphenoxy) 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 β exp values showed the following trend:C 4h (9.31×10 –10 mMW –1 )>D 2h (7.89×10 –10 mMW –1 )>Cs (7.32× 10 –10 mMW –1 ) > C 2v (1.77 × 10 –10 mMW –1 ). These results were similar to that obtained with the 4 β -(4- tert -butylphenoxy) phthalocyanines as the C 2v and C s isomers were found to have the lowest β exp values compared to other symmetries. The 4 β -(4- tert -butylphenoxy) phthalocyanine C 4h isomer was found toshowbetter non-linear optical properties compared to all other isomers. Keywords: Phthalocyanine, non-linear optical absorption, density functional theory, magnetic circular dichroism