Synthesis And Study Of Pyrocatechol Deriatives As Sensors For The Recognition Of Boric Acid

Boric acid is widely used in food, chemical industry, medical science and other fields, and its detection is one thing we concern at all times. Optical chemosensors are widely used in detection of anions and cations, and the colormetric chemosensors attract the chemistry workers for their direct naked recognition without any expensive equipments. Dyes possess strong chromogenesis, performing well in recognition. Refering to the above matter, this dissertation designed and synthesized a range of dyes, studying their application in recognizing boric acid, the results are summarized as follow:1. The concepts, principles and recent development of supermolecular, molecular recognition and topical chemosensor are briefly introduced, the measures of detection of boric acid are summarized.2. Recognition of boric acid by the common pyrocatechol deriatives alizarin was studied by UV-Vis. It was found that alizarin could form a complex with boric acid at pH 9.0 Na2HPO4-NaH2PO4 buffer solution. The process induced an obvious blue shift, and the color of the solution turned rose to orange, yet the addition of ordinary anions, almost had no changes and cations (masked by EDTA) and anions did not disturb the recognition reation. The mechanism of recognizing boric acid with alizarin was discussed preliminarily, and compared with the mechanism of recognizing anions with alizarin.3. Three pyrocatechol azobenzene derivatives were synthesized and their reactions with boric acid and some ordinary anions,cations were studied by UV-vis at pH 8.3 EDTA-NaOH. It was found that each receptor formed a complex in 1:1 binding model through the o-hydroxy of phenolic with boric acid, the process led to a blue shift of the each recptor's absorption spectrum.The corresponding color of the solution changed remarkablely, while the addition of ordinary anions or cations didn't induce such changes. The result showed the title compound could selectively recognize boric acid, easily observed by naked eyes. Electron-donating group is in favor of the proceeding of recognition, while the chromophore benefits the naked recognition.4. Two azoanthraquinone dyes, bearing o-hydroxy of phenolic as recognition site, azo group and anthraquinone group as signal group were synthesized and their reactions with boric acid, anions and cations at EDTA-NaOH buffer solution were studied by UV-Vis spectrophotometry. It showed that boric acid could induce the absorption spectrum of each receptor a specificity change, following obvious solution color changes, which could observe by naked eye. The Job plots indicated a 1:1 stoichiometric relation between each receptor and boric acid and ordinary ions did not disturb recognition.