Raman spectra of tetraoxa[8]circulenes. p-dinaphthalenodiphenylenotetrafuran and its tetraalkyl derivatives (DFT study and experiment)

The equilibrium molecular geometry, harmonic vibrational frequencies, and Raman band intensities were calculated by the density functional theory B3LYP method with the 6-31G(d) basis set for tetraoxa[8]circulenes p-dinaphthalenodiphenylenotetrafuran (p-2B2N) and p-dinaphthaleno-2,3,10,11-tetraethyldiphenylenotetrafuran (p-2B2N4R, R = C2H5) whose molecules belong to D-2h and D-2 point group symmetry. All bands in the measured Raman spectrum of p-dinaphthaleno-2,3,10,11-tetraundecyldiphenylenotetrafuran (p-2B2N4R, R = n-C11H23) were assigned based on quantum-chemical calculations of the frequencies and normal vibration modes of the molecule. A comparison of the calculated vibrational spectra with those from the experiment made it possible to assign reliably all observed bands in the Raman spectrum. Results of quantum-chemical calculations were in good agreement with the experimental data.