Coumarin-based Fluorescent Molecular Sensors And Alcoholic Hydroxyl Silyl Ether Selectivity Xie Protection Research

Considerable research interest has been focused on the development of chemosensors for the selective and efficient detection of chemically and biologically important ionic species in biological and environmental science during the last 20 years. Two novel fluorescent chemosensors were synthesized in this paper, to explore further the utility of them as an selective fluorescence chemosensoe recognition for these metal ions and diammonium molecular. We also have developed a facile and efficient procedure for the cleavage of alcoholic TBS ethers 1. Two novel fluorescent chemosensors in which two aza-18-crown-6 moieties or two morpholide moieties are linked to a coumarin fiuorophore were synthesized and investigated for their photochromic and fluorescence properties. It was found that the chemosenosr bearing two aza-18-crown-6 moieties could selectively recognize Fe³⁺. In fluorescence titration studies, this chemosensor displayed 15-flod fluorescence enhancement for Fe³⁺ among 13 metal ions investigated. To explore further the utility of the chemosensor as an selective fluorescence chemosensoe for Fe³⁺ the competition experiments were conducted in the presence of 1 equiv. of Mg²⁺,Ca²⁺, Cu²⁺, Zn²⁺, Co²⁺, Ni²⁺, Mn²⁺, Hg²⁺ and Pb²⁺ as well as the mixture of the metal ions in buffered HEPES solution (0.1M, pH = 7.4), respectively. No obvious interference was observed in fluorescence while performing the titration with in the physiological important metal ions. The above results implied that its selectivity for Fe³⁺ was remarkable in physiological conditions. Its absorption enhancedlinearly with the concentration of Fe³⁺((0.0⁰.2mM),R = 0.9904)) up to a ratio (1/Fe³⁺) of (1:1), and there it remained. We thought this fluorescence enhancement was attributed to Ï€-stacking interactions between chemosensor 1 and Fe³⁺ ions in the 1:1 complex formed. On the other hand, to explore further the utility of chemosensor in which two morpholide moieties recognition fo these metal ions, no significant variation in its fluorescence intensity was found.2. The photochromic and fluorescence properties of chemosenosr 1 for recognition of diammonium molecular were investigated by absorption and fluorescence measurements. It was found that the chemosenosr bearing two aza-18-crown-6 moieties could recognize diammonium. In fluorescence titration studies, chemosensor 1 displayed 20-98% fluorescence quenching in the presence of 100 equiv. of 5 different diammonium (from 1,6-diaminohexane to 1,10-diaminodecane ) investigated in CH3OH-H2O(9:l/v/v) buffer solution(0.1M, pH = 4.0) condition, particularly it was 98% fluorescence quenching for 1,8-diaminoctane. The above results implied that chemosenosr 1 for the recognition of the 1,8-diaminoctane was remarkable in this condition. We thought this fluorescence quenching was attributed to 7i-stacking interactions between chemosensor 1 and 1,8-diaminoctane ions in the 1:1 or 1:2 complex formed by the hydrogen bonding. On the other hand, to explore further the utility of chemosensor in which two morpholide moieties recognition for those diammonium , no significant variation in its fluorescence intensity was found.3. We also have developed a facile and efficient procedure for the cleavage of alcoholic TBS ethers using 0.5 equiv. SnCl2-2H2O in EtOH-H2O (10:1) at room temperature. The method is specific for deprotection of primary alcoholic TBS ethers. The phenolic TBS ethers, secondary and tertiary alcolholic TBS ethers, and the extensively used TBDPS-, acetyl-, benzyloxycarbonyl-, /?-toluenesulfonyl- and benzyl- protective groups remained to be not touched. To explore further that the glucose with both primary and secondary hydroxyl TBS ethers gave a primary hydroxyl-deprotected product.