Theoretical investigation of naphthodithiophene diimide derivatives as fluorescent sensors for 2,4,6-trinitrophenol detection.

CONTEXT

This study explored the geometry, aromaticity, electrostatic potential, and fluorescence sensing capability of N,N'-dimethyl naphthodithiophene diimide (C-NDTI-S) and its derivatives (C-NDFI-O and C-NDPI-N), where thiophene rings were substituted with furan and pyrrole, respectively. Theoretical calculations revealed that C-NDTI-S had the most negative adsorption energy for 2,4,6-trinitrophenol (TNP), and its electronic absorption spectrum and fluorescence spectrum decreased considerably upon TNP adsorption. Through FMO, hole-electron, independent gradient model, and energy decomposition analysis, it was revealed that the essence of fluorescence quenching is the intermolecular weak π-π interaction driving photo-induced electron transfer. Furthermore, C-NDFI-O and C-NDPI-N generated by modifying the structure of C-NDTI-S have the potential to serve as more efficient fluorescent sensors for TNP detection. The fluorescence recovery times confirmed the suitability of the three compounds as fluorescence probes.

METHODS

In this study, the Gaussian 09 software package at B3LYP-D3(BJ)/6-311 +  + G** level was applied to optimize the structure, energy, and fluorescence recovery time. Multiwfn combined with VMD software package was used to analyze the aromaticity of compounds using LOL-π and HOMA, with a focus on the differences in aromaticity after thiophene was substituted with different rings. Using AMBER force field for energy decomposition analysis based on force field (EDA-FF), the weak intermolecular interaction components are decomposed. The independent gradient model analysis based on Hirshfeld partition analysis clearly demonstrates the π-π interactions between molecules, with the δ parameter set to 0.005 a.u. Electron absorption spectroscopy, charge-transfer spectra spectroscopy, molecular interactions, and hole electron interactions were all completed with the help of Multifwn software.