Solvent Effect on the Third-Order Nonlinear Optical Properties of α- and β-Tertbutyl Phenoxy-Substituted Tin(IV) Chloride Phthalocyanines.

This paper investigates the third-order nonlinear optical properties of 4α-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (α-SnOtBpPc) and 4β-(4-tert-butylphenoxy) phthalocyaninato dichlorotin(IV) (β-SnOtBpPc) in different organic solvents. The third-order susceptibilities of α-SnOtBpPc and β-SnOtBpPc are reported in different solvents, using Z-scan techniques with 10 ns laser pulses at 532 nm. Their nonlinear absorption coefficient and absorption cross sections were also determined. The molecular imaginary components of the second-order hyperpolarizability Im[γ] of α-SnOtBpPc and β-SnOtBpPc were found to be 2.60 × 10-31 and 2.94 × 10-31 esu (tetrahydrofuran), 2.12 × 10-31 and 2.54 × 10-31 esu (chloroform), 3.06 × 10-31 and 2.54 × 10-31 esu (dichloromethane), and 1.27 × 10-31 and 1.50 × 10-31 esu (toluene), respectively. This study found that substitution at the α position has an effect of lowering the two-photon (2PA) cross section value for α-SnOtBpPc compared to that for β-SnOtBpPc, with values of 64.30 and 456.65 GM, respectively. The large 2PA cross section observed in β-SnOtBpPc is attributed to the decreased energy difference between the virtual state and the LUMO.