Optical limiting properties of non-fluorescent 1,3,5,7-tetraarylazaBODIPY dyes on the nanosecond timescale at 532 nm

In this study, the optical limiting properties of a series of 1,3,5,7-tetraarylazaBODIPY dyes were studied on the nanosecond timescale by carrying out open-aperture Z-scan measurements at 532 nm with the second harmonic of an Nd:YAG laser. 1,3,5,7-tetraphenylazaBODIPY (azaBDY) was structurally modified at the para-positions of the proximal (3,5-) and distal (1,7-) ring positions by adding bromine atoms and morpholine (1), piperidine (2) and pyrrolidine (3) rings, respectively. Negligible fluorescence was observed along with very low singlet oxygen quantum yield values, since the introduction of the lone pair of the nitrogen atoms of the para-substituents at the distal positions results in intramolecular charge transfer effects and large dipole moments. Z-scan measurements were conducted at 48 [Formula: see text]M for 1–3 with a fixed laser pulse energy of 40 [Formula: see text]J and a pulse width of 7 ns. Key optical limiting parameters such as the effective nonlinear absorption coefficient ([Formula: see text]), the second-order hyperpolarizability ([Formula: see text]), the imaginary component of the third-order susceptibility (Im[[Formula: see text]]) and the limiting fluence (I[Formula: see text]) values were analyzed to identify trends in the structure-property relationships of the azaBODIPY dyes.