Synthesis, Metal Ion Complexation, and Emission Studies of Naphthalimide Based Fluoroionophores

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Synthesis, Metal Ion Complexation, and Emission
Studies of Naphthalimide Based Fluoroionophores Je
ffrey 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.