A colorimetric and ratiometric fluorescent sensor for biogenic primary amines based on dicyanovinyl substituted phenanthridine conjugated probe

Two molecules with an aldehyde donor substituted 4'-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-carbaldehyde (5) and a dicyanovinyl acceptor substituted 2-((4'-(7,8,13,14-tetrahydrodibenzo[a,i]phenanthridin-5-yl)-[1,1′-biphenyl]-4-yl)methylene)malanonitrile (7) were synthesized, and both were applied to remarkable solvatochromism studies. Due to their intramolecular charge transfer (ICT) characteristic, both fluorophores, with a positive solvatochromism effect and emission color, changed from blue to green-orange when the polarity was increased from non-polar hexane to polar acetonitrile solvent. Meanwhile, for compound 5 and 7, aggregation induced emission (AIE) and acidochromism studies have been carried out. The obtained results indicated that compound 5 and 7 exhibited tunable aggregation induced emission and quenching of acidochromism for 7. In this study, we have proposed a new method based on dicyanovinyl substituted phenanthridine moiety of 7 for selective and efficient recognition of biogenic primary amines (BPAs), based on the interaction between amine and the dicyanovinyl-linked phenanthridine moiety of 7. It can be cleaved quickly with significant changes in fluorescence (from orange to blue) that produced 7-imine with induced ratiometric fluorescence. UV–visible/fluorescence spectral titration, NMR, mass spectra and DFT spectroscopic studies were proved by the mechanism of amine sensing. Limit of detections 3.67 nM (DA), 28.3 nM (EDA), 65.3 nM (HA) and 15.8 nM (n-BA) are also obtained for this probe 7 with remarkable ratiometric fluorescence enhancement. Additionally, fluorescence test paper with probe (7) was also fabricated and utilized to detect amines.