Palladium-catalyzed synthesis of trans-4-(N,N-bis(2-pyridyl)amino)stilbene. A new intrinsic fluoroionophore for transition metal ions.

[reaction: see text] The title compound (1) has been synthesized via sequential Pd-catalyzed amination reactions and investigated as an intrinsic fluoroionophore. The efficiency in the synthesis of 1 strongly depends on the order of couplings among the substrates. Compound 1 displays fluorescence quenching upon the binding of transition metal ions, where the binding-triggered conformational twisting and in turn the inhibition of internal charge transfer (ICT) play an important role.