Z-scan study of nonlinear absorption in novel lanthanide bis-phthalocyanines

We report our results on the nonlinear absorption of novel sandwich lanthanide(III) double-decker complexes BuPc2Ln (BuPc = 2,3,9,10,16,17,23,24-octabutyl-phthalocyaninate; Ln = Eu, Dy, Er, Lu) studied in tetrahydrofuran (THF) solution using open aperture z-scan technique with 350 ps laser pulses at 532 nm. All the compounds exhibit reverse saturable (RSA) absorption. With approaching to the focus a weak saturation of absorption was observed, while at the focus a strong decrease in transmittance took place. Employing the rate equations formalism we demonstrate RSA being mainly contributed by the triplet state absorption.