The Synthesis And Properties Of Fluorescence Molecular Probes And Related Crystals Based On Naphthalimide

As an effective detecting method, fluorescence molecular probes work based on fluorescence spectral changes when interaction occurs between the sensing unite and specific analyte, so that the substance can be detected. As compared with the traditional analytical instruments, fluorescence molecular probes exhibit significant advantages including high selectivity and sensitivity, fast response, easily handling, non-invasive, convenient and real-time sensing. Therefore, this detection method is widespreadly used in chemistry, life sciences, basic medicine, environmental detection and other fields. As a special class of excellent fluorophores, 1,8-naphthalimide derivatives are attracting considerable attention, because of their high fluorescence quantum yield, good optical and chemical stability, large Stokes shift and excellent chemical modification. In this paper, the design, synthesis and spectroscopic properties of 1,8-naphthalimide fluorescence molecular probes have been investigated, the main achievements are as follows:1. Pd+4+ fluorescence molecular probe based on Claisen rearrangementFluorescence molecular probe P1 was synthesized by 4-bromo-1,8-naphthalic anhydride and charactered by elemental analyses, NMR and MS spectrum. Naphthalimide has a good planarity and large conjugated system, and with an electron donor and an acceptor group, as a result, P1 showed blue emission with high fluorescence intensity in Na₂CO₃/NaHCO₃ ?pH=10? buffer. P1 exhibited a high fluorescence quantum yield of 66.72% and a large Stokes shift of 82 nm, in addition, the fluorescence lifetime was 4.78 ns. Upon the increase of Pd+ concentration ?0-45 ?M?, a gradual decrease in fluorescence intensity and color changes were observed. Argument with a series of data, the detection mechanism was based on Claisen rearrangement. The resulting fluorescent probe not only discriminated Pd from competing Pt species, but also distinguished Pd in an oxidation state without altering its oxidation states from Pd⁰. With the experiment condition optimized, the probe exhibited a liner response for Pd2+ from 10 to 45 ?M, with a detection limit of 1.4 ?M.2. Fluorescence molecular probe for detection of water in organic solventsIn order to improve the sensitivity of fluorescence molecular probe based on 1,8-naphthalimide, P2 was synthesized by introducing substituents into position 3 and 4 of the naphthalimide ring simultaneously, which had a high sensitivity for detection of water in organic solvents. The solvent-dependent fluorescence spectral characteristics of P2 have been studied in a serious of organic solvents, including acetonitrile, DMF, DMSO. As the solvent polarity increasing, the fluorescence maxima exhibited a marked bathochromic shift and simultaneously fluorescence intensity decreased. Owing to the formation of intra- and intermolecular hydrogen bonds with the increase of water content, the fluorescence intensity of P2 decreased in three organic solvents. P2 fluorescence emission intensity changes as a function of water content in the 0.00-4.25%?v:v? range in acetonitrile, and a linear of 0.00-1.50%?v:v? and a detection limit of 0.005%?v:v? were achieved. In addition, a linear of 0.00-11.50%?v:v? and a detection limit of 0.08%?v:v? and a linear of 0.00-15.00%?v:v? and a detection limit of 0.11%?v:v? were achieved in DMF and DMSO. Fluorescence molecular probe P2 had highest sensitivity in acetonitrile. Unfortunately, the chemical structure of P2 was not determined.3. Synthesis and characterization of crystalsTwo crystals of N3 and N7 were synthesized and their single structures were charactered by X-ray diffraction, which confirmed their chemical structures.