Zn(ii)-coordination-driven chiroptical and emissive sensing for chiral amines using a quaterphenyl-5′-carbaldehyde

Abstract

Quaterphenyl-5′-carbaldehyde 1 with metal ion coordination ability was synthesized for the first time and used for chiral analyte-binding and chiroptical sensing. The formation of an imine between 1 and amine analytes, such as alcohol amines, diamines, and amino acids, enabled Zn(II)-assisted chiral transfer from the analyte to the atropisomeric biphenyl unit, thereby amplifying the circular dichroism (CD) signal, leading to discernible Cotton effects in the range of 350–450 nm, with g values on the order of magnitude of 10⁻³ in MeOH. Linear relationships between the CD amplitude and enantiomer excess (ee) of the analytes were observed, enabling use of 1 as a chiroptical probe for amines. Interestingly, 1 showed a fluorescence response to change in concentrations of L-phenylalaninol ((S)-G1) in the presence of Zn(II) upon excitation at 380 nm. It suggests that 1 could serve as a dual chemosensor for the determination of both the ee and concentration of analytes. The Zn(II)-assisted fluorescence behavior was also subjected to circular polarization luminescence (CPL) measurements.