Comparative study of the structural and spectral properties of tetraaza- and tetraoxaannelated tetracirculenes

Abstract

The IR spectrum of a recently synthesized tetraaza[8]circulene (4N) molecule has been investigated and completely interpreted based on the calculation of the molecular structure and force field within the density functional theory (DFT) using the B3LYP/6-311G(d,p) method. The calculation has also successfully explained the X-ray diffraction data. The same method has been used to calculate the tetraoxa[8]circulene (4О) molecule and perform a comparative analysis of the IR spectra of both molecules. In contrast to 4О, the 4N molecule exhibits strong fluorescence, which hinders measurement of its Raman spectrum; hence, it is only predicted based on the DFT calculation in this study. A comparison of the IR and Raman spectra of the 4N molecule with the experimental and theoretical analogs for the 4О molecule has made it possible to assign all the observed vibrational transitions and explain the nature of normal vibrations in these complex molecules.