The synthesis and optical properties of three stilbene-type dyes

Three “D–π–A” stilbene-type dyes, namely trans-4-[p-(N,N-di (2-hydroxyethyl))-amino-styryl]-N-methyl pyridinium iodide (DHEASPI-C1), trans-4-[p-(N,N-di (2-hydroxyethyl))-amino-styryl]-N-octyl pyridinium bromide (DHEASPBr-C8) and trans-4-[p-(N,N-di (2-hydroxyethyl))-amino-styryl]-N-dodecyl pyridinium bromide (DHEASPBr-C12) were synthesized and their optical properties in different environments were investigated. Red shifts occurred in both the one-photon and two-photon fluorescence spectra from DHEASPI-C1 to DHEASPBr-C8 and to DHEASPBr-C12 as the alkyl group in the terminal acceptor was changed from methyl through octyl to dodecyl. When a 1064 nm, <130 fs mode-locked Nd: YAG laser pulse was pumped, their lasing locations occurred at 613–624 nm. When DHEASPI-C1 was used as reference, the two-photon absorption cross-sections (σs) of DHEASPBr-C8 and DHEASPBr-C12 were 8.02 and 13.5, respectively.