6.4. IR Vibrational spectra
The theoretical and experimental IR spectra of the studiedmolecules
are shown in Figs. 8 and S8 (Supplementary data). The calculated wave
numbers and intensities of 6a–i obtained from the B3LYP/6-311G(d,p)
method were collected in Table S9 (Supplementary Information).
Since the calculated frequencies are in general overestimate the experimental
data so the vibrational frequencies calculated at B3LYP/6-
311G(d,p) level of theory were scaled by 0.9670 in order to correct
the calculated harmonic frequencies [55]. Generally, the scaled infrared
vibrational frequencies showed good agreementwith the experimental
data. Fig. 9 showed good correlations between the calculated and the
experimental wave numbers (R2= 0.9961–0.9995). The IR fundamental
modes were collected and assigned in Table 6. Herein the descriptions
of the most important modes were presented.