Poly(amidoamine) dendrimer peripherally modified with 4-N,N-dimethylaminoethyleneamino-1,8-naphthalimide as a sensor of metal cations and protons (original) (raw)
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Polymer, 2007
Two new fluorescent second generation poly(propyleneimine) dendrimers, peripherally modified with 1,8-naphthalimide, have been synthesized for the first time and characterized. The photophysical characteristics of the new dendrimers have been studied in organic solvents of different polarity. The effect of the chemical nature of the 1,8-naphthalimide C-4 substituent on the photophysical properties of new dendrimers is discussed. The complexes formed between the dendrimers and the metal cations in solution have been studied, with regard to potential applications as fluorescent sensors for metal ion contamination. The results show that the C-4 substituent determines both the response to the presence of metal cations and the selectivity of the sensors.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2006
The paper reports on the spectral photophysical characteristics of two new fluorescent PAMAM dendrimers of zero and second generation decoreted with 1,8-naphthalimide units, designed for ionic detection. The dendrimers were studied by 1 H NMR, 13 C NMR, FT-IR spectroscopy and elemental analysis. Their ability to detect ions has been evaluated in acetonitrile by monitoring the quenching of the fluoresence intensity. Different ions have been tested: Zn 2+ , Co 2+ , Ni 2+ , Cu 2+ and Fe 3+ for the purpose. The results have shown clearly that only Zn 2+ could be efficiently detected using the dendrimer of second generation. In addition, it has been shown that for both dendrimers in a acetonitrile-water solution, the fluoresence intensity is pH dependant, hence could find application as a detector of harmful pH changes in the environment.
Journal of Polymer Science Part A: Polymer Chemistry, 2007
An inexpensive and highly efficient synthesis of first example of fluorescent aromatic dendrimers having alternative ether and urea linkages without the need for protection and deprotection steps has been developed. Dendrons and dendrimers up to third generation, with amine end-groups, were prepared by convergent growth approach in high yield. A repetitive synthetic sequence of nucleophilic addition reaction between amine and regenerated isocyanate and reduction of nitro groups into amine are adopted for the synthesis of these dendrimers. The peripheries of the dendrimers contained 6, 12, and 24 amino groups, for the first, second, and third generation, respectively. Materials were characterized by FTIR, NMR, and MALDI-TOF MS spectrometry. These dendrimers were soluble in amide solvents, THF and acetone and displayed fluorescence maxima in the 440-500 nm range with relatively narrow peak widths indicating that they had pure and intense fluorescence. These dendrimers form chargetransfer (CT) complexes with electron acceptor molecules such as 7,7,8,8,-tetracyanoquino-dimethane and 1,1,2,2 tetracyanoethane as evidenced by UV-visible absorption spectra. V
Fluorescent Dendrimers As Sensors for Biologically Important Metal Cations
Current Medicinal Chemistry, 2012
The review presents fluorescence spectroscopic studies on the capacities of newly synthesized polypropyleneamine and polyamidoamine fluorescent dendrimers to detect biologically important metal ions. It has been shown that those fluorescent dendrimers whose periphery comprises 1,8-napthalimide fragments are highly sensitive to metal ions which are of great importance to the living organisms.
Polymer Degradation and Stability, 2006
The colouristic and fluorescent characteristics of a new composite material based on a PAMAM dendrimer of second generation whose periphery is modified with 4-N,N-dimethylaminoethylamino-1,8-naphthalimide and polyamide-6 have been investigated. This dendrimer has been investigated with regard to its application as a heterogenic sensor capable of detecting metal cations and protons in aqueous solutions. In the presence of metal cations (Ni 2þ , Fe 2þ , Fe 3þ and Co 2þ ) and protons the fluorescence intensity of the composite increases due to their coordination with dendrimer molecule. The results obtained reveal the capacity of this system to act as a sensitive sensor of environmental pollution by metal cations and protons. It has been shown that in N,N-dimethylformamide solution the metal cations inhibit the processes of photodegradation of the dendrimer.
Chemphyschem, 2004
We report the absorption spectra and the photophysical properties (fluorescence spectrum, quantum yield, and lifetime) of four dendrimers of the poly(propylene amine) family (POPAMs) functionalized at the periphery with naphthylsulfonamide (hereafter called naphthyl) units. Each dendrimer Gn, where n=1 to 4 is the generation number, comprises 2n+1(i.e., 32 for G4) naphthyl functions in the periphery and 2n+1−2 (i.e., 30 for G4) tertiary amine units in the branches. All the experiments have been carried out in acetonitrile solutions. Comparison with two reference compounds (N-methyl-naphthalene-2-sulfonamide, A, and N-(3-dimethylamino-propyl)-2-naphthalene-1-sulfonamide, B) has shown that the absorption spectra of the dendrimers are significantly different from those expected from the component units. Furthermore, the intense fluorescence band of the naphthyl unit (λmax=343 nm; Φ=0.15, τ=8.5 ns) is strongly quenched in the dendrimers. The quenching effect increases with increasing generation and is accompanied by the appearance of a weak and broad emission tail at lower energy. Protonation of the amine units of the dendrimers by addition of CF3SO3H (triflic) acid causes a strong increase in the intensity of the naphthyl luminescence and a change in the form of the emission tail. The shapes of the titration curves depend on dendrimer generation, but in any case, the effect of the acid can be fully reversed by successive addition of a base (tributylamine). The results obtained show that in the dendrimers there are interactions (both in the ground and excited states) between naphthyl units as well as between naphthyl units and amine units of the branches; this gives rise to dimer/excimer and charge-transfer/exciplex excited states. Titration with Zn(CF3SO3)2has the same effect as acid titration, as far as the final emission spectrum is concerned, but a much higher concentration of Zn(CF3SO3)2has to be used and the shapes of the titration plots are very different. Titration with Co(NO3)2.6H2O causes a much smaller increase in the intensity of the naphthyl fluorescence compared with Zn(CF3SO3)2. The results obtained have shown that protonation and metal coordination can reveal the presence of ground and excited state electronic interactions in functionalized poly(propylene amine) dendrimers, and that the presence of photoactive units in the dendrimers can be useful to reveal some peculiar aspects of the protonation and metal coordination processes.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2008
The investigations aim at revealing the ability of a 1,8-napthalimide-modified poly(amidoamine) dendrimer from second generation to respond to the presence of cuprum cations and protons in the environment. It has been established that a single Cu 2+ cation present in the dendrimer molecule is capable of quenching more than 78% of its fluorescence what is an indication of high sensitiveness. An enhancement of the fluorescence emission of the dendrimer has been observed in acidic medium. It has been established that the processes of coordinating the ions in different sites of the dendrimer are reversible.