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/IBC
≤ ...4.2 and Class + 1 with log1/IBC
> 4.2, the unit of IBC
: mol/L) by utilizing a large data set of 601 toxicity log1/IBC
of organic compounds to
. 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 (
= 253.8 and
= 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/IBC
), of 80.0% for the test set (150 log1/IBC
), and of 86.9% for the total data set (601 log1/IBC
), 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
.
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 -NO
increase the strength of the hydrogen bond, while electron-giving groups such as -N(CH
)
and -OCH
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.
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 CO2−· 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.
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
) 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
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.
The effects of substituent X and Y on ultraviolet (UV) absorption properties of stilbene compounds XPhCHCHPhY (XSBY) were studied both experimentally and computationally from the viewpoint of UV ...maximum absorption wavelength (λmax) and the corresponding energy (υmax). In the studies, the contribution of substituents on υmax shift was explored. The results show that with increase of electron withdrawing or electron donating ability of X or Y, there is an enhanced electron delocalization of XSBY that leads to bathochromic shift. Computational analyses based on density functional theory were conducted to elucidate the phenomena. It is disclosed that the υmax values are significantly affected by the excited state, though the electronic effect of ground state cannot be ignored. Finally, on the basis of the respective influences of X and Y, a quantitative model, which was proved reliable by the leave-one-out method, was developed to scale the effects of terminal substituents on υmax. According to the model, the effects of substituents X or Y exhibit almost the same action on υmax owing to the symmetric skeleton of the XSBY compounds. The findings provide deep insight into the effects of terminal substituents on UV absorption properties of stilbene compounds, and the derived model enables practical expression of the relationship between substituents and UV absorption.
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•Electron withdrawing or donating substituent leads to bathochromic shift of λmax.•Ground-state and excited-state effect of X and Y have a significant influence on υmax.•Computational analyses were conducted to clarify the experimental phenomena.•A reliable quantitative model has been developed to scale the effects of substituents on υmax.
The C–X bonds of organic compounds between group X and a saturated or unsaturated carbon atom differ in bond energy. To identify the causes of variation is of great significance in terms of bond ...nature understanding and bond energy estimation. In this paper, the electronegativity χX of group X was calculated by the “valence electron equalized electronegativity” method. Then, χX and the electronic effect constant of the substituent were taken as variables to establish equations for quantitative correlation between C(sp3)–X and C(sp2)–X for the calculation of C–X bond energies. The aim is make comparison between substituted methane, Me–X, and substituted benzene, Ph–X, as well as that between Me–X and substituted ethylene, C2H3–X. We conducted calculation over 40 compounds that contain different X groups, and the results reveal that the C(sp3)–X and C(sp2)–X bond energies are under the influence of a number of factors. In addition to the covalent properties of C and X atoms and χX, the bond energies of C(sp2)–X (i.e., DC(sp2)–X) are under the influence of the field/inductive effect (σFX) and conjugated effect (σRX) of group X, with the former causing a decrease while the latter an increase of DC(sp2)–X. Using the acquired quantitative correlation equations and on the basis of a relatively rich set of measured DMe–X data, we estimated DPh–X of Ph–X and DC2H3–X of C2H3–X, and the estimation accuracy is within experimental uncertainty. Employing the above method, the DC(sp2)–X of 33 substituted benzenes, 53 substituted ethenes, and 82 α-substituted naphthalenes was estimated with satisfactory outcomes.
The random forest (RF) algorithm, together with ten Dragon descriptors, was used to develop a quantitative structure–toxicity/activity relationship (QSTR/QSAR) model for a larger data set of 1792 ...chemical toxicity pIGC50 towards Tetrahymena pyriformis. The optimal RF (ntree =300 and mtry =3) model yielded root mean square (rms) errors of 0.261 for the training set (1434 chemicals) and 0.348 for the test set (358 chemicals). Compared with other QSTR models reported in the literature, the optimal RF model in this paper is more accurate. The feasibility of applying the RF algorithm to predict chemical toxicity pIGC50 towards Tetrahymena pyriformis has been verified.
► Seven crystals of bis-Schiff bases suitable for X-ray diffraction were obtained. ► Term sinτ is suitable to modify the substituent effects on the νmax. ► Dihedral angle τ has a limited effect on ...the values of δC(CN).
The relationship between the molecular conformation and spectroscopic properties of symmetrical bis-Schiff bases was explored experimentally. Seven samples of compounds p-X–C6H4CHNC6H4NCHC6H4–p-X (X=OMe, Me, Et, Cl, F, CF3, or CN) were prepared for this study, and their crystal structures were measured by X-ray diffraction. Their λmax values in ethanol, acetonitrile, chloroform and cyclohexane solvents were measured, and their δC(CN) values in chloroform-d were determined. The results show that the νmax is dependent on the substituents at the benzylidene ring and the dihedral angle τ of the titled molecules, and the term sin(τ) is suitable to modify the substituent effects on the νmax. However, experimental investigations indicate that the dihedral angle τ has a limited effect on the values of δC(CN). This study provides a new understanding for the molecular conformation on spectroscopic properties of symmetrical Schiff bases.
Developing photocatalysts to steer conversion of solar energy toward high-value-added fine chemicals represents a potentially viable approach to address the energy crisis and environmental issues. ...However, enablement of this conversion is usually impeded by the sluggish kinetic process for proton-coupled electron transfer and rapid recombination of photogenerated excitons. Herein, we report a simple and general structural expansion strategy to facilitate charge transfer in conjugated microporous polymers (CMPs) via engineering the donor surrounding the trifluoromethylphenyl core. The resulting CMPs combine high surface area, strong light-harvesting capabilities, and tunable optical properties endowed by extended π-conjugation; the optimized compound CbzCMP-5 generated from 9,9′,9″-(2-(trifluoromethyl)benzene-1,3,5-triyl)tris(9H-carbazole) remarkably enhanced the photogenerated carrier transfer efficiency, enabling the functionalization of thiophenols toward thiocarbamates and 3-sulfenylindoles with high photocatalytic efficiency. Most importantly, the in-depth insights into the carrier-transfer processes open up new prospects on further optimization and rational design of photoactive polymers for efficient charge-transfer-mediated reactions.
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