Spectral properties of bisphenol F based on quantum chemical calculations

• Sequence of electron transition in three bisphenol F isomers from difficulty to ease is 2,2′-BPF, 2,4′-BPF, and 4,4′-BPF.
• The FTIR absorption peak strength of the 4,4′-BPF increases significantly in a polar solvent.
• The Raman spectra variation of the 4,4′-BPF in the polar solvent is limited.
• New characteristic peaks occur in the FTIR spectra and Raman spectra along with an increase in the hydroxyl group amount.
• The order of the red shifts in the UV spectra is opposite of the order of the substitution element electronegativity values.

The quantum chemical calculation method is used in this paper to study the energy difference between the highest occupied molecular orbitals and lowest unoccupied molecular orbitals of three bisphenol F (BPF) isomers. The results show that the minimum energy difference occurs at 4,4'-dihydroxydiphenylmethane (4,4′-BPF); the middle energy difference occurs at 2,4'-dihydroxydiphenylmethane (2,4′-BPF); and the maximum energy difference occurs at 2,2'-dihydroxydiphenyl- methane (2,2′-BPF). Based on these results, the electron transition in 4,4′-BPF is easier than that in 2,4′-BPF, while the electron transition in 2,2′-BPF is the most difficult. This paper investigates the effect of the hydroxyl group, specifically concerning the spectroscopic properties of BPF isomers by observing the solvent effect, hydroxyl group amount and the element substitution of an oxygen atom in the hydroxyl group. The solvent effect results show that infrared spectroscopy intensity increases significantly for 4,4′-BPF in the polar solvent (methanol and water), but does not increase proportionally to the electric constant increase of the polar solvent. The multi hydroxyl substitution of BPF isomers results show that with an increase in the hydroxyl group amount, new characteristic peaks occur in FTIR spectra and Raman spectra, while the characteristic peaks in UV spectra are smoother in the range of 240–300 nm. The element substitution results show that the red shifts occur in a different element substituted 4,4′-BPF isomer in UV spectra, and the red shifts order is opposite of that involving substitution element electronegativity.