1. Synthesis, Metal Ion Complexation, and Emission Studies of Naphthalimide Based Fluoroionophores
Jeffrey E. Elbert, Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, Iowa, 50614
Fluorescence enhancement of 4-substituted alkylpolyamino-butyl-1,8-naphthalimides upon addition of sub-ppm concentrations of transition metal ions is being investigated for potential use in a variety of systems including trace metal analysis in biochemical and environmental systems. Our study of the derivatives, DMED4, DEED4, and MMED4 found a greater increase in fluorescence enhancement with alkyl substitution on the distal amine as compared to the unsubstituted derivative ED4 (ethylenediamine derivative). There was lesser shift of the long wavelength emission to the blue than observed with ED4 and selectivity was observed for larger metal ions such as Pb2+ instead of smaller metal ions such as Cu2+.
In these respects, the derivatives studied behave comparably to the butanediamine derivative studied previously. These results are quite interesting as the effect of alkyl substitution on the distal nitrogen could be a steric effect or a donating effect, increasing basicity. The increase in chain length of the butanediamine derivative as compared to the ethylenediamine derivative would appear to be a steric effect. Continued study of emission properties as well as computational work will allow us to examine and separate the steric and basicity effects.