Three-stage pH-switchable organic second-order nonlinear optical (SO NLO) chromophores are synthesized and characterized by wavelength-dependent linear and nonlinear spectroscopy. The chromophores exhibit huge SO NLO responses in their “on” stages, and large switching contrasts between adjacent stages in both SO NLO response and fluorescence quantum yield, with moreover different “on/off” sequences for closely related compounds.
This work has been partially supported by National Research Foundation of Korea (NRF) grants funded by the Korea government (2014R1A5A1009799, 2016R1A2B4011050, and 2009-0093826). Financial support from the Fund for Scientific Research-Flanders (FWO; projects No. G040011N, G02112N, 1512716N, G020612N, G052213N, G035918N, G036618N and the EOS CHARMING project G0F6218N [EOS-ID 30467715]) is gratefully acknowledged.
