The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the...The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the computational cost and higher precision to the best for large systems. The performance of DFT, double-hybrid DFT, and high-level com- posite methods are examined. The tested sets contain monocyclic and polycyclic aromatic molecules, branched hydrocarbons, small inorganic molecules, etc. The results show that the mPW2PLYP and G4MP2 methods achieve reasonable agreement with the benchmark val- ues for most tested molecules, and the mean absolute deviations are 2.43 and 1.96 kcal/mol after excluding the BDEs of branched hydrocarbons. We recommend the G4MP2 is the most appropriate method for small systems （atoms number≤20）; the double-hybrid DFT methods are advised for large aromatic molecules in medium size （20≤atoms number≤50）, and the double-hybrid DFT methods with empirical dispersion correction are recommended for long-chain and branched hydrocarbons in the same size scope; the DFT methods are ad- vised to apply for large systems （atoms number〉50）, and the M06-2X and B3P86 methods are also favorable. Moreover, the differences of optimized geometry of different methods are discussed and the effects of basis sets for various methods are investigated.展开更多
The formation and breaking of Ni-L （L=N-heterocyclic carbene, tertiary phosphine etc.） bond is involved in many Ni-catalyzed/mediated reactions. The accurate prediction of Ni-L bond dissociation enthalpies （BDEs） ...The formation and breaking of Ni-L （L=N-heterocyclic carbene, tertiary phosphine etc.） bond is involved in many Ni-catalyzed/mediated reactions. The accurate prediction of Ni-L bond dissociation enthalpies （BDEs） is potentially important to understand these Ni-complex involving reactions. We assess the accuracy of diffierent DFT functionals （such as B3LYP, M06, MPWB1K, etc.） and diffierent basis sets, including both effective core potentials for Ni and the all electron basis sets for all other atoms in predicting the Ni-L BDE values reported recently by Nolan et al. [J. Am. Chem. Soc. 125, 10490 （2003） and Organometallics 27, 3181 （2008）]. It is found that the MPWB1K/LanL2DZ：6-31＋G（d,p）//MPWB1K/LanL2DZ：6-31G（d） method gives the best correlations with the experimental results. Meanwhile, the solvent effect calculations （with CPCM, PCM, and SMD models） indicate that both CPCM and PCM perform well.展开更多
The C-I bond dissociation enthalpies （BDE） of various organic iodides were calculated using high-level theoretical methods including MP2 and CCSD（T） with extrapolated basis set as well as a number of density funct...The C-I bond dissociation enthalpies （BDE） of various organic iodides were calculated using high-level theoretical methods including MP2 and CCSD（T） with extrapolated basis set as well as a number of density functional theory methods. After systematic evaluation of the theoretical results against available experimental C-I BDEs, it was found that the MPW LYPIM method gave the lowest root mean square error. We, therefore, used this method to examine the substituent effects on different categories of C（sp3）-I and C（sp2）-I bonds. Fur thermore, the remote substituent effects on the C-I BDEs of substituted iodobenzenes and substituted （iodomethyl）benzenes were also investigated at the same level. The C-I BDEs of typical heteroaromatic iodides including five-membered and six-membered heterocyclic iodides were also examined.展开更多
Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3P...Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3PW91, B3P86） methods together with 6-31G^＊＊ and 6-311G^＊＊ basis sets. The results show that B3P86/6-311G^＊＊ method is the best method to compute the reliable BDEs for substituted chlorobenzene compounds which contain the C-C1 bond. It is found that the C-C1 BDE depends strongly on the computational method and the basis sets used. Substituent effect on the C-C1 BDE of substituted chlorobenzene compounds is further discussed. It is noted that the effects of substitution on the C-C1 BDE of substituted chlorobenzene compounds are very insignificant. The energy gaps between the HOMO and LUMO of studied compounds estimate the relative thermal stability ordering are also investigated and from this data we of substituted chlorobenzene compounds.展开更多
The iridium hydride complexes have been extensively used in organic reactions,such as oxidation and hydro-genation reactions.In many of these reactions,the dissociation or formation of Ir-H bond plays an important rol...The iridium hydride complexes have been extensively used in organic reactions,such as oxidation and hydro-genation reactions.In many of these reactions,the dissociation or formation of Ir-H bond plays an important role in determining the overall reaction rates and yields.In the present study,the accuracy of different theoretical meth-ods for prediction of Ir-H bond strengths has been examined on the basis of the previously reported Ir-H BDEs of 17 different complexes.Comparing the performance of different DFT functionals(e.g.B3LYP,TPSS,M06),different basis sets(including the different effective core potentials(ECP)on Ir and I atoms,and the total electron basis sets on the other atoms),and different solvation models(SMD,CPCM,and IEFPCM)in solution phase single point calculations,we found that the gas-phase calculation with TPSS/(LanL2DZ:6-31G(d))method is relatively more accurate than the other gas-phase calculation methods,and can well simulate the Ir-H BDEs in low-polarity solvents(such as chlorobenzene and dichloroethane).Finally,efforts were put in analyzing the structure-activity re-lationships between the ligand structure(around Ir center)and the Ir-H BDEs.We wish the present study could benefit future studies on the Ir-H complexes involved organic reactions.展开更多
The static O-H bond parameters including O-H bond length, O-H charge difference, O-H Mulliken population and O-H bond stretching force constant (k) for 17 phenols were calculated by ab initio method HF/6-31G**. In com...The static O-H bond parameters including O-H bond length, O-H charge difference, O-H Mulliken population and O-H bond stretching force constant (k) for 17 phenols were calculated by ab initio method HF/6-31G**. In combination with the O-H bond dissociation enthalpies (BDE) of the phenols determined by experiment, it was found that there were poor correlationships between the static O-H bond parameters and O-H BDE. Considering the good correlationship bt tween O-H BDE and logarithm of free radical scavenging rate constant for phenolic antioxidant, it is reasonable to believe that the ineffectiveness of static O-H bond parameters in characterizing antioxidant activity arises from the fact that they cannot measure the O-H BDE.展开更多
文摘The density functional theory （DFT） is the most popular method for evaluating bond dis- sociation enthalpies （BDEs） of most molecules. Thus, we are committed to looking for alternative methods that can balance the computational cost and higher precision to the best for large systems. The performance of DFT, double-hybrid DFT, and high-level com- posite methods are examined. The tested sets contain monocyclic and polycyclic aromatic molecules, branched hydrocarbons, small inorganic molecules, etc. The results show that the mPW2PLYP and G4MP2 methods achieve reasonable agreement with the benchmark val- ues for most tested molecules, and the mean absolute deviations are 2.43 and 1.96 kcal/mol after excluding the BDEs of branched hydrocarbons. We recommend the G4MP2 is the most appropriate method for small systems （atoms number≤20）; the double-hybrid DFT methods are advised for large aromatic molecules in medium size （20≤atoms number≤50）, and the double-hybrid DFT methods with empirical dispersion correction are recommended for long-chain and branched hydrocarbons in the same size scope; the DFT methods are ad- vised to apply for large systems （atoms number〉50）, and the M06-2X and B3P86 methods are also favorable. Moreover, the differences of optimized geometry of different methods are discussed and the effects of basis sets for various methods are investigated.
基金This work was supported by the National Nature Science Foundation of China （No.21325208, No.21172209, No.21202006, No.21361140372）, the Anhui Provincial Natural Science Foundation （No.1308085QB38）, the Specialized Research Fund for the Doctoral Program of Higher Education （No.20123402110051）, the Financial Resources Federal Credit Union （No.WK2060190025, No.FRF-TP-13-023A）, the Science Foundation of the Chinese Academy of Sciences （No.JCX2-EW-J02）, the Fok Ying Tung Education Foundation, the ChinaGrid project funded by MOE of China and the supercom- puter center of Shanghai and USTC.
文摘The formation and breaking of Ni-L （L=N-heterocyclic carbene, tertiary phosphine etc.） bond is involved in many Ni-catalyzed/mediated reactions. The accurate prediction of Ni-L bond dissociation enthalpies （BDEs） is potentially important to understand these Ni-complex involving reactions. We assess the accuracy of diffierent DFT functionals （such as B3LYP, M06, MPWB1K, etc.） and diffierent basis sets, including both effective core potentials for Ni and the all electron basis sets for all other atoms in predicting the Ni-L BDE values reported recently by Nolan et al. [J. Am. Chem. Soc. 125, 10490 （2003） and Organometallics 27, 3181 （2008）]. It is found that the MPWB1K/LanL2DZ：6-31＋G（d,p）//MPWB1K/LanL2DZ：6-31G（d） method gives the best correlations with the experimental results. Meanwhile, the solvent effect calculations （with CPCM, PCM, and SMD models） indicate that both CPCM and PCM perform well.
文摘The C-I bond dissociation enthalpies （BDE） of various organic iodides were calculated using high-level theoretical methods including MP2 and CCSD（T） with extrapolated basis set as well as a number of density functional theory methods. After systematic evaluation of the theoretical results against available experimental C-I BDEs, it was found that the MPW LYPIM method gave the lowest root mean square error. We, therefore, used this method to examine the substituent effects on different categories of C（sp3）-I and C（sp2）-I bonds. Fur thermore, the remote substituent effects on the C-I BDEs of substituted iodobenzenes and substituted （iodomethyl）benzenes were also investigated at the same level. The C-I BDEs of typical heteroaromatic iodides including five-membered and six-membered heterocyclic iodides were also examined.
基金This work was supported by the National Natural Science Foundation of China （No.10774039）.
文摘Quantum chemical calculations were used to estimate the bond dissociation energies （BDEs） for 13 substituted chlorobenzene compounds. These compounds were studied by the hybrid density functional theory （B3LYP, B3PW91, B3P86） methods together with 6-31G^＊＊ and 6-311G^＊＊ basis sets. The results show that B3P86/6-311G^＊＊ method is the best method to compute the reliable BDEs for substituted chlorobenzene compounds which contain the C-C1 bond. It is found that the C-C1 BDE depends strongly on the computational method and the basis sets used. Substituent effect on the C-C1 BDE of substituted chlorobenzene compounds is further discussed. It is noted that the effects of substitution on the C-C1 BDE of substituted chlorobenzene compounds are very insignificant. The energy gaps between the HOMO and LUMO of studied compounds estimate the relative thermal stability ordering are also investigated and from this data we of substituted chlorobenzene compounds.
基金We thank the National Natural Science Foundation of China(NSFC,Nos.21325208,21172209,21202006,21361140372)Specialized Research Fund for the Doc-toral Program of Higher Education(SRFDP,No.20123402110051)+1 种基金Financial Resources Federal Credit Union(FRFCU,Nos.WK2060190025,FRF-TP-13-023A)Science Foundation of The Chinese Academy of Sciences(CAS,No.JCX2-EW-J02),Fok Ying Tung Education Foundation,China Grid Project funded by MOE of China and the supercomputer center of Shang-hai and USTC.
文摘The iridium hydride complexes have been extensively used in organic reactions,such as oxidation and hydro-genation reactions.In many of these reactions,the dissociation or formation of Ir-H bond plays an important role in determining the overall reaction rates and yields.In the present study,the accuracy of different theoretical meth-ods for prediction of Ir-H bond strengths has been examined on the basis of the previously reported Ir-H BDEs of 17 different complexes.Comparing the performance of different DFT functionals(e.g.B3LYP,TPSS,M06),different basis sets(including the different effective core potentials(ECP)on Ir and I atoms,and the total electron basis sets on the other atoms),and different solvation models(SMD,CPCM,and IEFPCM)in solution phase single point calculations,we found that the gas-phase calculation with TPSS/(LanL2DZ:6-31G(d))method is relatively more accurate than the other gas-phase calculation methods,and can well simulate the Ir-H BDEs in low-polarity solvents(such as chlorobenzene and dichloroethane).Finally,efforts were put in analyzing the structure-activity re-lationships between the ligand structure(around Ir center)and the Ir-H BDEs.We wish the present study could benefit future studies on the Ir-H complexes involved organic reactions.
文摘The static O-H bond parameters including O-H bond length, O-H charge difference, O-H Mulliken population and O-H bond stretching force constant (k) for 17 phenols were calculated by ab initio method HF/6-31G**. In combination with the O-H bond dissociation enthalpies (BDE) of the phenols determined by experiment, it was found that there were poor correlationships between the static O-H bond parameters and O-H BDE. Considering the good correlationship bt tween O-H BDE and logarithm of free radical scavenging rate constant for phenolic antioxidant, it is reasonable to believe that the ineffectiveness of static O-H bond parameters in characterizing antioxidant activity arises from the fact that they cannot measure the O-H BDE.
基金the Guangdong Provincial Natural Science Foundation of China(003062) Guangdong Provincial Science and Technology Planning Projects of China(2003C20406)
