The Solvent Effect In Molecular Recognition Of Fluorescent Probes Based On Triphenylene, Coumarin And Naphthalimide

The study of fluorescent probes is a rapidly developing field of supramolecular chemistry. Three types of probes with triphenylene, coumarin and 1,8-naphthalimide fluorophores were designed for the detection of metal ions or water molecules. Their sensitivity to solvent polarity and recognition ability were studied through the UV and FL spectra.As an analogue of pyrene, triphenylene has been seldom reported in the study of fluorescent sensors. Herein triphenylene probes linked by different heterochain receptors were designed. The titration experiment indicates that probes with dithioether moiety had good selectivity to Hg²⁺. The addition of Hg²⁺ induces about a 76-fold decreases in fluorescence intensities of A4 containing 1-aminotriphenylenen, while A2 with 2-aminotriphenylenen showed a bathochromic shift of the emission maximum.Two probes with mono-imine (B2) and bis-imine (B3) attached to coumarin fluorophore were designed for the detection of metal ions. It is found that both the probes were selectively decomposed by Cu²⁺ in CH3CN, then Cu²⁺ could be detected by measuring the fluorescent intensity of 7-(N,N-diethylamino)-coumarin-3-aldehyde (B1). At the same time, the selectivity of B2 and B3 to metal ions in several solvents were investigated as well, the results demonstrated that solvent effects had much influence on sensing process.A series of N-hetroaryl-1,8-naphthalimides had been designed and synthesized, which showed good sensitivity to solvent polarity according to the study of photophysical properties. The typical compound 4-(1-piperidyl)-N- (2-pyrimidinyl)-1,8-naphthalimide (D3) was chosen as a fluorescence sensor to determine the water content in six common solvents (p-dioxane, THF, acetone, DMF, acetonitrile and methanol). The fluorescence intensity changes as a function of water content correlate well with a modified Stern-Volmer equation over a wide range. The detection limits are 0.016% and 0.020% for acetone and THF, respectively.