Synthesis and Characterization of Fluorescent Poly(aromatic amide) Dendrimers

The synthesis of a series of poly(aromatic amide) dendrimers up to the second generation is described
herein. The AB2 building block used throughout the synthesis of the dendrimers was the allyl ester
of 3,5-diaminocinnamic acid, which has been synthesized from 3,5-dinitrobenzoic acid in good yield
with use of a four-step procedure. Dendron synthesis was achieved via a convergent approach with
use of a sequence of deprotection/coupling steps. Two commercially available alcohols, l-menthol
and citronellol, were coupled to the AB2 monomer by using an alkyl diacid spacer and two core
units; 1,7-diaminoheptane and tris(2-aminoethyl)amine have been used to produce the final
dendrimers. Characterization was carried out by NMR and IR spectroscopies, MALDI-TOF mass
spectrometry, GPC, and DSC. The novel monomer and dendritic derivatives exhibited a strong
fluorescence emission in the visible region (λ ≈ 500 nm) of the spectrum and a weak emission in
the near-infrared (λ ≈ 850 nm) upon excitation in the near-UV region. The fluorescence emission
characteristics were found to be solvent and dendrimer generation dependent.