Date of Award

11-19-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

First Advisor

Anamitro Banerjee

Abstract

This work is a study of a new class of aromatic amines as fluorescent zinc sensors. N-(Carboxymethyl)-N-[3-[(carboxymethyl)amino]-2-methoxy-5-methylphenyl]glycinate exhibits more than 20-fold fluorescence enhancement in the presence of Zn(II) ions when excited at 300 nm. This compound shows a fluorescence emission at 390 nm, which in the presence of Zn(II) ion exhibits a 20 nm emission blue shift. The tetraacetate version, potassium N,N'-(2-methoxy-5-methyl-1,3-phenylene)bis[ N-(carboxymethyl)]glycinate, exhibits a 7-fold sensitivity to Zn(II) ion, and there is no emission band shift observed. Investigations point to the methoxy group for the ratiometric behavior and increased sensitivity to zinc. The diacetate versions—sodium N-(carboxymethyl)- N-(2-methoxyphenyl)glycinate, sodium N,N'-(2-methoxy-5-methyl-1,3-phenylene)bisglycinate and sodium N,N'-dimethyl-N,N'-(2-methoxy-5-methyl-1,3-phenylene)bisglycinate—had no fluorescent selectivity to zinc. The absence of the methoxy group in sodium N,N'-1,3-phenylenebis[N-(carboxymethyl)]glycinate and sodium N-(carboxymethyl)-N-[3-[(carboxymethyl)amino]phenyl]glycinate affected the sensitivity to Zn(II) significantly. When the methoxy group was displaced from between the amino functions such as in sodium N-[special characters omitted](carboxymethyl)-N-[3-[(carboxymethyl)amino]-4-methoxyphenyl]glycinate,[special characters omitted]the selectivity to zinc was lost. The presence of a nitro group para to the methoxy group as in sodium N,N'-(2-methoxy-5-nitro-1,3-phenylene)bisglycinate and sodium N,N'-(2-methoxy-5-nitro-1,3-phenylene)bis [ N(carboxymethyl)]glycinate also destroyed the selectivity to Zn(II) even though the wavelength of excitation was increased significantly. Introducing the nitro function ortho to one of the amino groups such as in so-[special characters omitted]dium N,N'-(2-methoxy-4-nitro-1,3-phenylene)bis[ N-(carboxymethyl)]glycinate, increased the wavelength of excitation to 365 nm, but significantly reduced the selectivity to zinc and the stability of the molecule. Replacing the methoxy group with a methyl fragment as in sodium N-(carboxymethyl)-N-[3-[(carboxymethyl)amino]-2-methylphenyl]glycinate also destroyed the selectivity of the sensor to zinc.

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