2,4-Dihydroxybenzophenone is the most widely used molecule in the benzophenone group of UV absorbers. It is known that the UV absorption ability is dependent on the substituents. Numerous studies have shown that the strength of intramolecular hydrogen bonds is the main factor affecting this type of UV absorber. However, the effect of substituents on the formation and nature of the hydrogen bonds has not been well studied. In this work, the effect of the type of substituent and the substitution position on the absorption intensity of 2,4-dihydroxybenzophenone molecules is verified both experimentally and theoretically. The effect of substituents on the intramolecular hydrogen bonding of 2,4-dihydroxybenzophenone was investigated by DFT calculations. The results indicate that the addition of different substituents leads to various changes in the strength of the hydrogen bonding in 2,4-dihydroxybenzophenone. On the X-substitution site or the Y-substitution site, halogen groups and electron-absorbing groups such as -CN and -NO₂ increase the strength of the hydrogen bond, while electron-giving groups such as -N(CH₃)₂ and -OCH₃ decrease the strength of the bond. For the same substituent, the one at the Y site has a higher effect on hydrogen bonding than that at the X site. By NBO analysis, it was found that the substituents would cause charge redistribution of the individual atoms of 2,4-dihydroxybenzophenones, thus affecting the formation and strength of the hydrogen bonds. Moreover, when the substituent is at the Y substitution site, the oxygen atom of the carbonyl group is less able to absorb electrons and more charge is attracted to the oxygen atom of the hydroxyl group, resulting in a larger charge difference between the two oxygen atoms and an increase of bond energy. Finally, a multiple linear regression analysis of the NPA charge number of the atoms involved in the formation of the hydrogen-bonded chelated six-membered ring was performed with the energy of the hydrogen bond and the percentage of influencing factors estimated, which were found to jointly affect the strength of hydrogen bonding. The aim of this study is to provide theoretical guidance for the design of benzophenone-based UV absorbers that absorb UV light of specific wavelength bands.

Substituent effects on the ultraviolet absorption properties of 2,4-dihydroxy dibenzophenone were investigated experimentally. Nine compounds of 2,4-dihydroxy dibenzophenone with different substituents were prepared by a solvent-free reaction of benzoyl chloride. The maximum absorption wavelength (λ_max) of these samples was measured, and their UV resistance properties in cotton fabric as well as in polyester were determined. The results show that the λ_max is dependent on the substituents at the benzylidene ring, and both electron donating substituents and electron withdrawing substituents cause a bathochromic shift. The UV resistance of fabric increases with the increase in compound concentration. The dyeing rate of each compound on polyester was higher than that of cotton. On cotton fabric, the dyeing rate of 2,4-dihydroxybenzophenone was the highest, 77.8%. On polyester, that of 2,4-dihydroxy-4′-ethyl dibenzophenone was the highest, 84.1%. The study provides new insights into the effect of substituents on the properties of 2,4-dihydroxy dibenzophenone that are related to the whitening of cotton and polyester materials.

Vibrio fischeri is widely used as the model species in toxicity and risk assessment. For the first time, a global classification model was proposed in this paper for a two-class problem (Class − 1 with log1/IBC₅₀ ≤ 4.2 and Class + 1 with log1/IBC₅₀ > 4.2, the unit of IBC₅₀: mol/L) by utilizing a large data set of 601 toxicity log1/IBC₅₀ of organic compounds to Vibrio fischeri. Dragon software was used to calculate 4885 molecular descriptors for each compound. Stepwise multiple linear regression (MLR) analysis was used to select the descriptor subset for the models. The ten molecular descriptors used in the classification model reflect the structural information on the Michael-type addition of nucleophiles, molecular branching, molecular size, polarizability, hydrophobic, and so on. Furthermore, these descriptors were interpreted from the point of view of toxicity mechanisms. The optimal support vector machine (SVM) model (C = 253.8 and γ = 0.009) was obtained with the genetic algorithm. The SVM classification model produced a prediction accuracy of 89.1% for the training set (451 log1/IBC₅₀), of 80.0% for the test set (150 log1/IBC₅₀), and of 86.9% for the total data set (601 log1/IBC₅₀), which are higher than that (80.5%, 76%, and 79.4%, respectively) from the binary logistic regression (BLR) model. The global SVM classification model is successful, although it deals with a large data set in relation to the toxicity of organics to Vibrio fischeri.

This study explores the electrochemical reduction in CO₂ using room temperature ionic liquids as solvents or electrolytes, which can minimize the environmental impact of CO₂ emissions. To design effective CO₂ electrochemical systems, it is crucial to identify intermediate surface species and reaction products in situ. The study investigates the electrochemical reduction in CO₂ using a cobalt porphyrin molecular immobilized electrode in 1-n-butyl-3-methyl imidazolium tetrafluoroborate (BMI.BF4) room temperature ionic liquids, through in-situ surface-enhanced Raman spectroscopy (SERS) and electrochemical technique. The results show that the highest faradaic efficiency of CO produced from the electrochemical reduction in CO₂ can reach 98%. With the potential getting more negative, the faradaic efficiency of CO decreases while H₂ is produced as a competitive product. Besides, water protonates porphyrin macrocycle, producing pholorin as the key intermediate for the hydrogen evolution reaction, leading to the out-of-plane mode of the porphyrin molecule. Absorption of CO₂ by the ionic liquids leads to the formation of BMI·CO₂ adduct in BMI·BF₄ solution, causing vibration modes at 1100, 1457, and 1509 cm⁻¹. However, the key intermediate of ${\mathrm{CO}}_2^{-}·$ radical is not observed. The υ(CO) stretching mode of absorbed CO is affected by the electrochemical Stark effect, typical of CO chemisorbed on a top site.