Optical limiting properties of free base porphyrins and their Sn(IV) complexes on the nanosecond timescale

The optical limiting properties of a series of free base porphyrin dyes and their Sn(IV) complexes were analyzed on the nanosecond timescale in the visible region at 532 nm with the second harmonic of an Nd:YAG laser by the open-aperture Z-scan technique. The effect of introducing different meso -aryl groups was investigated with 2-bromophenyl ( 1 ), 3-bromophenyl ( 2 ), 4-bromophenyl ( 3 ), and methyl ester phenyl ( 4 ) groups and the corresponding Sn(IV) complexes ( 1–4-Sn ). The most significant optical limiting parameters, including the effective nonlinear absorption coefficient (β eff ), the imaginary component of the third-order susceptibility (Im[χ (3) ]), the second-order hyperpolarizability (γ), and the limiting fluence (I lim ) values, were analyzed to identify trends in the structure-property relationships. More favorable reverse saturable absorption responses were observed for dyes with para -substituted meso -aryl rings, and for the Sn(IV) complexes relative to the free base dyes.