Mechanistic Insights on Chemosensing Response of Pyrene and Anthracene Based Fluorescent Probes Towards Nitroaromatic Compounds.

Two polyaromatic hydrocarbon-based compounds, N,N,N-tris-((pyren-1-yl)methyl)-1,3,5-triazine-2,4,6-triamine (SM1) and N,N,N-tris-((anthracen-9-yl)methyl)-1,3,5-triazine-2,4,6-triamine (SM2) are explored as chemosensors for detecting nitroaromatic compounds. The chemosensing studies of SM1 and SM2 showed selective sensing of 4-nitroaniline (4NA) in homogeneous medium (in Acetonitrile (ACN) and in DMSO), which is due to the hyperpolarizability of 4NA. Quenching mechanism studied for the three analytes (4NA, 2NA and PA) showed dynamic quenching in SM1 in presence of 4NA and 2NA, while static quenching in presence of PA. Solvent effect on the chemosensing response of SM1 and SM2 towards PA was observed and it showed enhancement in the response on changing the solvent from ACN to DMSO to water. DFT studies, photophysical analysis, NMR experiments and complex synthesis experiments were done to provide in depth analysis on the observed sensing phenomena. Both SM1 and SM2 being insoluble in water, were used as heterogeneous chemosensors in aqueous medium, where selective sensing was observed for 4NA and PA. The LOD of PA and 4NA by SM1 in water was found to be 1.3 ppt and 2.1 ppt, respectively. The recyclability and stability after sensing studies were confirmed by PXRD.