Vibrational spectra study of fluorescent dendrimers built from the cyclotriphosphazene core with terminal dansyl and carbamate groups

The FTIR and FT Raman spectra of the Janus-type dendrimers, possessing five carbamate groups on one side and five fluorescent dansyl derivatives on the other side, with amide G(1) and hydrazone G(2) central linkages were studied. These surface-block dendrimers are obtained by the coupling of two different dendrons. The FTIR and FT-Raman spectra of the zero generation dendrons, built from the hexafunctional cyclotriphosphazene core, with five dansyl terminal groups and one carbamate G(0 nu) and one oxybenzaldehyde function G(0 nu)' have been recorded. The structural optimization and normal mode analysis were performed for dendron G(0 nu)' on the basis of the density functional theory (OFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that dendron molecule G(0 nu)' has a concave lens structure with planar -O-C6H4-CH=O fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of dendron G(0 nu)' were interpreted by means of potential energy distributions. Relying on DFT calculations a complete vibrational assignment is proposed. The strong band 1597 cm(-1) show marked changes of the optical density in dependence of substituents in the aromatic ring. The frequencies of nu(N-H) bands in the IR spectra reveal the presence of the different types of H-bonds in the dendrimers. (C) 2011 Elsevier B.V. All rights reserved.