Preparation And Fluorescence Behavior Of Supramolecular Complex Based Cyclodextrins-containing Chromophores

In this thesis, according to the principles of Fluorescence Resonance Energy Transfer (FRET), we chose dansyl (DNS),7-nitrobenzofurazan (NBD), FITC as the donors, rhodamine B as the acceptor. Due to its unique structural feature, cyclodextrin can keep the donor and acceptor within the effective distance of the Forster energy transfer. Based on the Hard Soft Acid Base (HSAB) principle, we changed the chemical structure of the metal-ion ligand, so that the supramolecular-complex exhibited specific ion selective recognition. These supramolecular complexs may find new applications in ion detection. The main contents and the results of this work are as follows:First, we synthesized mono-6-deoxy-6-dansyl-β-CD through the reaction of mono-6-deoxy-6-amino-β-CD with dansyl chloride; then, the guest AD-SRhB was synthesized by the process in which Rhodamine B was reacted with diethylenetriamine first, and then reacted with the activated 1-adamantanecarboxylic acid. The supramolecular-complex AD-SRhB/β-CD-DNS was prepared. Spectral analysis of AD-SRhB/β-CD-DNS supramolecular-complex confirms that the addition of Fe3+ can promote the formation of the open-ring state of the SRhB moieties and the excited energy of donor (linked on cyclodextrin rim) could be transfered to the acceptor(rhodamine B/Fe3+). The antidisturbance experiment shows that in the presence of multifarious cations, the AD-SRhB/β-CD-DNS supramolecular-complex has very good antidisturbance. In this system, efficient energy transfer can occurr between pH 4-7. Therefore, this FRET-based supramolecular sensor can be readily formed via an inclusion process using the donor part and the acceptor part, and can serve as a water-soluble ratiometric fluorescent sensor for Fe3+.According to the mechanism of Hard Soft Acid Base (HSAB), we changed the chemical structure of the ion-ligand to carbamido from imino in order to improve the softness of the "soft base". Therefore, we synthesized the host(HOST 1) with carbamido group and the guest(GUEST 3) with fluorescein moiety to form the supramolecular-complex HOST 1/GUEST 3. This supramolecular-complex showed good response toward Fe3+, as well as a certain response to Hg2+ in aqueous medium. In the HOST 1/GUEST 3 supramolecular-complex, the donor was within the hydrophobic cavity of cyclodextrin, so the fluorescence quantum yield of donor was improved. The antidisturbance experiment shows that in the present of multifarious cations including Hg2+, the HOST 1/GUEST 3 supramolecular-complex has quite good antidisturbance. Moreover, DNS-ADA and NBD-ADA were also synthesized as the donors. But we found that when DNS-ADA enters the hydrophobic cavity of cyclodextrin, the emission profile of DNS exhibited hypsochromic shifts markedly. It results in the energy level mismatch of DNS and the acceptor, hence the FRET of supramolecular-complex HOST 1/DNS-ADA can't occur. When the NBD-ADA was used as the donor, because of its strongly electron-withdrawing feature, the efficiency of energy transfer of supramolecular-complex HOST 1/NBD-ADA was limited. Therefore, FITC-ADA is the better donor for rhodamine B/Fe3+ complex for the FRET system.For detecting Hg2+, we further improved the "soft base" of the ligand by changing the chemical structure of ligand from carbamido group to thioureido group. Cyclodextrin with thioureido moiety was synthesized as HOST 2, and the FITC-ADA as the GUEST 3. The supramolecular-complex HOST 2/GUEST 3 was formed in aqueous solution. Spectral analysis of HOST 2/GUEST 3 supramolecular-complex confirms that thioureido moiety can improve the "soft base" of the ligand evidently and the ligand could complex with Hg2+ selectively. This strategy provides a water-soluble ratiometric fluorescent sensor for Hg2+. In the HOST 2/GUEST 3 supramolecular-complex, the addition of Hg2+ can promote the formation of the open-ring state of the SRhB moieties and the excited energy of donor (in cyclodextrin) could be transfered to the acceptor (rhodamine B/Hg2+ complex linked on cyclodextrin). The efficiency of energy transfer of the supramolecular-complex HOST 2/GUEST 3 reaches 90.2%.HOST 1/GUEST 3 supramolecular-complex has the very good antidisturbance. Its application in the environment and biological detection was investigated, for instance, Hg2+ detecting in tap water, in serum and urine. In summary, the supramolecular-complex HOST 2/GUEST 3 can serve as a water-soluble ratiometric fluorescent sensor for Hg2+, and can be used in environment and biological detection.