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dc.contributor.advisorHijji, Yousef M.
dc.contributor.authorBarare, Belygona Gesare
dc.contributor.departmentChemistryen_US
dc.contributor.programMaster of Scienceen_US
dc.date.accessioned2018-04-27T16:01:27Z
dc.date.available2018-04-27T16:01:27Z
dc.date.issued2009
dc.description.abstractThe synthesis and characterization of (E)-2-(2-hydroxybenzylideneamino)phenol (sensor 1), (E)-2-(2-hydroxybenzylideneamino)-5-nitrophenol (sensor 2), (E)-2-(2-hydroxybenzylideneamino)-4-nitrophenol (sensor 3), (E)-2-(2-hydroxy-5-nitrobenzylideneamino)-4-nitrophenol (sensor 4), (E)-2-(2- hydroxy-5-nitrobenzylideneamino)phenol (sensor 5) and (E)-2-((furan-2-ylmethylimino)methyl)phenol (sensor 6) are described. Sensors 1 - 6 were synthesized in one step from the condensation of salicylaldehyde or salicylaldehyde derivative and an appropriate aminophenol without solvent under irradiation from a microwave. These sensors comprises two parts; one is the anion binding part which is based on imine-phenol moieties and the other is a conjugated aromatic chromophore which converts binding induced changes into optical signals. The colorimetric and anion sensing properties of 1 - 6 towards anions such as F-, AcO-, H2PO4-, Br-, Cl-, ClO4- and HSO4- in CH3CN have been investigated. Visual inspection of solutions of the sensors before and after addition of F-, AcO- and H2PO4- ions resulted in dramatic colorimetric changes that were clearly visible to the naked eye. Upon binding to F-, AcO- and H2PO4-, the sensors displayed large bathochromic shifts in their UV/vis and fluorescence emission spectra. Colorimetric and UV/vis experiments showed that 1 and 6 had a strong selectivity for F- while 2, 3, 4 and 5 had a strong affinity for F-, AcO- and H2PO4-. Addition of Br-, Cl-, ClO4- and HSO4- to the acetonitrile solutions of the sensors resulted in very weak colorimetric and spectral changes. Job's plots showed a 1:2 binding between 1, 2, 4, 5 and 6 with F- while 3 showed a 1:1 binding to F-, AcO- and H2PO4- ions. In CH3CN-H2O mixture (9:1, v/v), sensor 3 discriminated AcO- from F- and H2PO4-. The binding constants of 1 - 6 were determined by UV/vis titration in CH3CN and analyzed by Benesi-Hildebrand expression. The calculated binding constants in the presence of selective anions were indicated to decrease in the order of 4 > 3 >5 > 2> 1 > 6. The selectivity of the studied anion sensors was also shown to decrease in line with the following order of the studied anions; AcO- > F- > H2PO4-. Fluorescence experiments indicated that sensors 1, 2 and 6 showed selective binding for F- whereas 3, 4 and 5 showed selective binding to the more basic ions (F-, AcO- and H2PO4-). The extent of conjugation, nature and position of the electron withdrawing -NO2 substituent in the structure of the sensors was observed to enhance anion selectivity. X-ray structures of 3 and 4 indicated that the compounds existed as iminio-phenolate zwitterions in solid state. The 1H-NMR and 13C-NMR results indicated that 3 and 4 existed as zwitterions in solution form. From the changes in the absorption and fluorescence spectra, proton transfer mechanisms have been deduced. In ground states, a two step process has been observed: first, the formation of the sensor-anion hydrogen-bond complex [LH...X] and secondly, the anion-induced deprotonation of the complex to form L- and HX2. In the excited states, the excited-state intermolecular proton transfer aided in the deprotonation of the sensors.
dc.genretheses
dc.identifierdoi:10.13016/M22Z12S5V
dc.identifier.urihttp://hdl.handle.net/11603/10657
dc.language.isoen
dc.relation.isAvailableAtMorgan State University
dc.rightsThis item is made available by Morgan State University for personal, educational, and research purposes in accordance with Title 17 of the U.S. Copyright Law. Other uses may require permission from the copyright owner.
dc.subjectFluoridesen_US
dc.subjectOrganic chemistryen_US
dc.subjectAnions--Analysisen_US
dc.subjectColorimetric analysisen_US
dc.titleSynthesis And Colorimetric Characterization Of Salicylidene Derivatives As Anion Sensors
dc.typeText


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