Intramolecular charge transfer and sensing mechanism for a colorimetric fluoride sensor based on 1,8-naphthalimide derivatives

Abstract

The sensing mechanism of a fluoride colorimetric chemosensor 4-(tert-butyldimethylsilyloxy)-Nbutyl-naphthalimide has been studied with density functional theory and time-dependent density functional theory methods. The theoretical results suggest that the low barrier of the desilylation reaction is responsible for the rapid response speed to the fluoride anion of the chemosensor. The calculated vertical excitation energies in the ground state of the chemosensor and its desilylation product agree well with the experimental UV-Vis absorbance spectra. It is also found that the intramolecular charge transfer process of the first excited state of the desilylation product induces the redshift of the absorbance and fluorescence spectra of the desilylation product compared with that of the chemosensor. Further, the previously experimentally incorrect assignment of the 1 H NMR spectrum of the desilylation product has been rectified in the present theoretical study.

Theoretical Elaboration about Excited State Behaviors and Fluoride Anion Sensor Mechanism for 2-{[2-(2-Hydroxy-Phenyl)-1H-Benzoimidazo-5-yl]-Phenyl-Methylene} Malononitrile

“…The corresponding chemical stable structures for these complexes are shown in Figure 4. The investigations about the binding energies between sensor itself and the anions should be reasonable for explaining the selectivity about anions [21][22][23][24][25][26][27][28][29][30]. As mentioned above, all the optimizations about all the complexes have been carried out via DFT/B3LYP/TZVP theoretical level in tetrahydrofuran solvent.…”

“…Generally, the fluorescence sensors could convert the discrimination of fluoride ions into the fluorescence emission signals. And most of the current fluoride ion chemosensors have been developed via fluoride mediated desilylation of Si-O bond using tert-butyldiphenylsilyl (TBDPS) and tertbutyldimethylsilyl (TBDMS) groups, fluoride anion induced deprotonation via pre-existing intra-or inter-molecular hydrogen bond, and so forth [21][22][23][24][25][26][27][28][29][30]. And in the aspect of experiment, the corresponding photophysical and photochemical characteristics are generally revealed via 1HNMR spectra, time-resolved absorption and emission spectra.…”

“…The HBPMM structure has been shown in Figure 1. As far as we know, the theoretical investigations about this type sensors are limited [21][22][23][24][25][26][27][28][29][30]. In experiment, just the indirect information about the structural and photochemical properties can be infrared based on experimental manner.…”

Computational, Structural and Spectroscopic Investigations of Two Polymorphs of 5,7‐Dinitro‐8‐(N‐phenylamino)Quinoline

“…The sensing mechanism of a fluoride colorimetric chemosensor 4‐(tert‐butyldimethylsilyloxy)‐N‐butyl‐naphthalimide has been previously reported . The photophysical properties and geometry were studied by 1 H NMR spectra, time‐resolved absorption spectra and fluorescence spectra in the study of the Si–O bond cleavage, ICT and ESPT processes …”

Sensing mechanism of a ratiometric near-infrared fluorescent chemosensor for cysteine hydropersulfide: Intramolecular charge transfer

“…Until now, numerous sensing mechanisms have been proposed and elucidated for designing fluorescent chemosensors, including the intramolecular charge transfer (ICT) 17,22,[30][31][32][33][34][35][36] , the photoinduced electron transfer (PET) 8,9,[37][38][39][40] , the excited state proton transfer (ESPT) 16,[41][42][43][44][45] , and the fluorescence resonance energy transfer (FRET) [46][47][48][49][50] . Thereinto, ICT mechanism is usually adopted to design the ratiometric fluorescent chemosensors 17,21,22,29,34,51,52 .…”