Synthesis, characterization and third-order nonlinear optical behaviour of three novel ethyne-linked donor/acceptor chromophores

Three novel ethyne-linked donor/acceptor chromophores, BAB, BAS and SAS were synthesized. The results of BAB in femtosecond and nanosecond Z-scan at 532 nm reveal that the transition from saturable absorption (SA) to reverse saturable absorption (RSA), while that of BAS and SAS display RSA. The femtosecond Z-scan results for all compounds at 600 nm–800 nm indicate the obvious RSA, which can be mainly attributed to the two-photon absorption (TPA). The TA results demonstrate that all compounds display strong excited-state absorption and long lifetime, and the evolution of TA spectra for these compounds reveals the relaxation process from the local excited-state (LE) to charge transfer state (CTS). With different conjugation extent and intramolecular charge transfer (ICT), the nonlinear response and excited-state dynamics of these chromophores could be dramatically modulated. The threshold of BAS/DCM solution excited at 532 nm with nanosecond pulse was 0.631 J/cm². The results indicate that these compounds may be the potential candidates for future application in optical limiting.