Two novel tetraphenylethylene-skeleton salamo-type fluorescent probes: specific recognition of cyanide through different response patterns

Based on tetraphenylethylene as the skeleton, two novel salamo-type fluorescent probes (TPES1 = 2-hydroxy-1-naphthaldehyde O-(3-(((-2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)amino)oxy)propyl) oxime and TPES2 = bis(2-hydroxy-1-naphthaldehyde O-(3-(((2-hydroxy-5-(1,2,2-triphenylvinyl)benzylidene)amino)oxy)propyl) dioxime) were designed and synthesized. Through the colorimetric and fluorescence dual-channel modes, cyanide ions could be specifically recognized by the two probe molecules. Interestingly, the probes TPES1 and TPES2 exhibited completely different spectral behaviors during the recognition process. Of the two, the TPES1 molecule is a ratio-type fluorescent probe, and double fluorescence emission peaks appeared during the titration process. The reason for this phenomenon is due to the rotation of the C–C single bond in tetraphenylethylene, causing the solution system to contain molecules in two states. On the other hand, the TPES2 molecule is a fluorescence-enhanced probe that has undergone two reaction processes of deprotonation and addition reaction successively, causing the fluorescence intensity to increase continuously. Theoretical calculations indicated that the configuration of probe TPES1 is reversed after interacting with cyanide ions (CN−). By calculating the minimum detection limits of TPES1 and TPES2 to CN−, the LOD values were 8.56 × 10−8 M and 5.37 × 10−8 M, respectively. In addition, probe-based test strips have been prepared for quick and simple detection of cyanide ions.