Ultrafast nonlinear optical studies of 3,8,13,18-Tetrachloro-2,7,12,17- tetramethoxyporphyrin and its derivatives

Recently we synthesized 3,8,13,18-tetrachloro-2,7,12,17-tetramethoxyporphyrin and its metallo-derivatives [1]. The free-base molecule is unique owing to the presence of an electron donating methoxy group and electron withdrawing chloro group on the adjacent β- positions of each pyrrole moiety. We could synthesize these molecules through two different routes; the first route provided pure isomer, albeit in low yield, whereas the second route provided mixture of isomers with higher yield [1]. Herein we report the third-order nonlinear optical properties of these porphyrins obtained from Z-scan measurements using ~40 fs, 800 nm pulses. Open aperture data confirmed the presence of saturable absorption whereas the closed aperture data indicated a positive nonlinearity. We have compared the data of the pure isomer with that of the mixture of isomers