Structural and spectroscopic properties of the second generation phosphorus–viologen “molecular asterisk”

Abstract The FTIR and FT Raman spectra of the second generation phosphorus–viologen “molecular asterisk” G 2 built from cyclotriphosphazene core with 12 viologen units and 6 terminal phosphonate groups have been recorded and analyzed. The experimental X-ray data of 1,1-bis(4-formylbenzyl)-4,4′-bipyridinium bis(hexaflurophosphate) was used in molecular modeling studies. The optimization of isolated 1,1-bis(4-formylbenzyl)-4,4′-bipyridinium (BFBP) molecule without counter ions PF 6 - does not lead to significant changes of dihedral angles, thus the molecular conformation does not depend on interactions with the counter ions. The structural optimization and normal mode analysis were performed for G 2 on the basis of the density functional theory (DFT). The calculated geometrical parameters and harmonic vibrational frequencies are predicted in a good agreement with the experimental data. It was found that G 2 has a kind of “egg timer” structure with planar O C 6 H 4 CH N N(CH 3 ) fragments and slightly non-planar cyclotriphosphazene core. The experimental IR and Raman spectra of G 2 were interpreted by means of potential energy distribution.