Design And Synthesis Of New Cation-Sensitive Fluorescent Probes Based On Rhodamin B And Aminonaphthalimide

The detection of the transition metal ions in aqueous solution are of currently significant importance for analytical chemistry because of its important roles in many fields including chemistry, biology, medicine (clinical biochemistry), and environment. Fluorescent probes can transfer molecular recognition events into fluorescence signals, which make a bridge between the molecular analytes and the analyst as an observer. The advantages of fluorescenct probes include high sensitivity of detection down to the single molecule, nice selectivity,"on-off"switchability, subnanometer spatial resolution and submillisecond temporal resolution, observation in situ, remote sensing with the application of fiber optics, etc. Due to their excellent properties, fluorescent sensors have been rapidly developed for various of transition metal ions.As is known to all, heavy and transition metal ions possess mostly empty orbits and can efficiently quench the fluorescence intensity of a fluorophore via enhanced spin-orbit coupling, electron and energy transfer. Thus, detection of heavy and transition metal ions by fluorescent sensors is operated mainly in fluorescence guenching mode. Due to the sensitivity reason, sensors showing fluorescence enhancement as a result of metal-ion binding are favored over those exhibiting fluorescence quenching. Fluorescent sensing heavy and transition metal ion based on fluorescence enhancement is a subject of intensive recent interest.Rhodamine-based fluorescent organic carriers have been widely used for conjugation with cations, owing to their excellent spectroscopic properties such as large molar extinction coefficient, high fluorescence quantum yield, excellent water solubility and low cost.In chapter 2, we synthesis a new chemosensor-Rhodamine B spirolactam derivative. Compared with compound reported, the new compound only changes one bond, but the properties changes a lot. The new compound was found to show a reversible dual chromo and fluorogenic response toward Cu2+ in aqueous solution in a highly selective and sensitive manner and other cations show no interference. The linear range covering from 2.5×10-6– 5.0×10-5 M, with a detection limit of 6.1×10-7 M.Because of the strong thiophilic affinity of Hg2+, we designed and synthesized another probe (Rhodamine B sulfur containing compound). Compared with Rhodamine B, by only replacing one atom at position 3, and thus only Hg2+ showed high affinity toward O, S atoms at positions 1 and 3 to open the spiro ring of the conpound, and the new dual chromo and fluorogenic sensor displays merits not only in its excellent selectivity and sensitivity, but also in the obvious color change against the colorless blank during the sensing process. The linear range covering from 5×10-6-1.4×10-5 M and a detection limit of 4.3×10-7 M.4-Aminonaphthalimide, frequently used as a fluorophore for fluorescent chemosensors, has desirable spectroscopic properties: excellent light stability, high quantum yield, moderate fluorescence emission wavelength, and large Stokes shift. We designed and synthesized a novel ratiometric chemosensor (piperazidine and 2, 6-bis(methyl)pyridine -linked aminonaphthalimide anthracene) for Hg2+ based on induced fluorescence resonance energy transfer (FRET) and photoinduced electron transfer (PET). The new chemosensor for mercury provided single-excitation, dual-emission detection. It exhibits a linear response toward Hg2+ in the concentration range 2.4×10-7-8.6×10-5 M with a high selectivity and a detection limit of 4.6×10-8 M.