A binding model study on TNP fluorescent sensor 4,40-(9,9 dimethylfluorene-2,7-diy1)dibenzoic acid

In this work, we mainly investigated the binding model for a 2,4,6-trinitrophenol(TNP) sensor 4,40-(9,9-dimethylfluorene-2,7-diy1)dibenzoic acid (DIB) by employing DFT and TDDFT methods. Roles of the hydrogen-bonding and pi-pi stacking interactions have been discussed in detail. Complexation energies and H-1 NMR spectra proved that the main binding model between DIB and TNP is the pi-pi stacking. Based on this proposed binding model, we further discussed the luminescence quenching of DIB when binding to TNP. The ground and excited state calculations indicated that the sensing mechanism can be attributed to photoinduced electron transfer (PET). In addition, we calculated the binding energies between DIB and different type nitro-explosives. Among these complexes, TNP complex has the highest binding energy, which explains the excellent selectivity of DIB for TNP molecule.