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We obtain gas-phase homolytic Al-H bond dissociation enthalpies (BDEs) at the CCSD(T)/CBS level for a set of neutral aluminium hydrides (which we refer to as the AlHBDE dataset). The Al-H BDEs in this dataset differ by as much as 79.2 kJ mol-1, with (H2B)2Al-H having the lowest BDE (288.1 kJ mol-1) and (H2N)2Al-H having the largest (367.3 kJ mol-1). These results show that substitution with at least one -AlH2 or -BH2 substituent exerts by far the greatest effect in modifying the Al-H BDEs compared with the BDE of monomeric H2Al-H (354.3 kJ mol-1). To facilitate quantum chemical investigations of large aluminium hydrides, for which the use of rigorous methods such as W2w may not be computationally feasible, we assess the performance of 53 density functional theory (DFT) functionals. We find that the performance of the DFT methods does not strictly improve along the rungs of Jacob's Ladder. The bestperforming methods from each rung of Jacob's Ladder are (mean absolute deviations are given in parentheses): the GGA B97-D (6.9), the meta-GGA M06-L (2.3), the global hybrid-GGA SOGGA11-X (3.3), the range-separated hybrid-GGA CAM-B3LYP (2.1), the hybrid-meta-GGA ÏωB97M-V (2.5) and the double-hybrid methods mPW2-PLYP and B2GP-PLYP (4.1 kJ mol-1). [ABSTRACT FROM AUTHOR]

The bond dissociation energies (BDE) of most main‐group elements have been accurately measured. However, the BDE values for heavy elements, particularly those from the fifth period (InI), are still missing or poorly validated. This study aims to identify the most accurate computational methods for calculating BDE values of compounds containing fifth‐row elements, including In, Sn, Sb, Te, and I, with a focus on readily accessible methods in software packages. The investigation involved a benchmark study using density functional theory (DFT), in addition to the 2nd order Møller–Plesset perturbation theory (MP2) and the coupled cluster with single, double, and perturbative triple excitations CCSD(T). The DFT functionals used in the study include APFD, B3LYP, B3LYP‐D3, B3P86, B97‐D3, BHandH, HSEH1PBE, M06‐2X, MN12‐SX, MN15‐L, and TPSSH. The functionals were carefully selected to cover some popular functionals as well as to cover all levels of the Jacob's ladder of DFT accuracy. The computed BDE values were compared with experimental values, and the results were filtered to remove any possible outliers. The statistical errors (MAPE, RMSE, and Pearson's) were then calculated and used to assess the performance of the methods. [ABSTRACT FROM AUTHOR]

In this study, the performance of 17 different density functional theory functionals was compared for the calculation of the bond dissociation energy (BDE) values of X−H (X=C, N, O, S) bonds of aromatic compounds. The effect of the size of the basis set (expansions of 6-31(G)) was also assessed for the initial geometry and zero-point energy calculations, followed by the single-point BDE calculations with different model chemistries with the 6-311 + (3df,2p) basis set. It was found that the size of the basis set for geometry optimization has a much smaller effect on the accuracy of BDE than the choice of functional for the following single-point calculations. The M06-2X, M05-2X and M08−HX functionals yielded highly accurate BDE values compared to experimental data (with the average mean unsigned error MUE = 1.2–1.5 kcal mol−1), performing better than any of the other functionals. The results suggest that geometry optimization may be performed with B3LYP functional and a small basis set, whereas the M06-2X, M05-2X and M08-HX density functionals with a suitably large basis set offer the best method for calculating BDEs of ArX−H (X=C, N, O, S) bonds.

The atomic and molecular properties of the title compounds were calculated by Jaguar using a basis set B3LYP/6-31G**++ with hybrid DFT in the gas phase, to determine the chemical reactivity. Analysis of quantum chemical features such as HOMO and LUMO explained that the electronic charge transfer occurred within the system through conjugated paths of the selected compounds. The nucleophilic and electrophilic reactive sites are recognized from the molecular electrostatic potential plot. Electrophilic and nucleophilic attack-prone molecular sites were predicted by mapping ALIE value to the molecular surface. The bond dissociation energy of the high active compound 15 (2-chloro-N-(2-(2-(2-(2-chlorobenzoyl)hydrazineyl)-2-oxoethoxy)phenyl)acetamide) was calculated to assess the probability of compound autoxidation or degradation. Further, molecular docking, binding free energy calculations, and ADMET profile of the degradation products (DPs) of compound 15 was carried out to determine the binding affinity and toxicity profile of the formed DPs compared with the parent compound. A 150-ns molecular dynamics (MD) simulation was performed to evaluate the binding stability of the compound 15/4URL complex using Desmond. Binding free energy and binding affinity of the complex were computed for 100 trajectory frames using the MM-GBSA approach. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Benchmark theoretical study is performed for homolytic cleavage of C Sn bond. • Nineteen DFs along with four basis sets are selected. • Theoretical results are compared with the experimental data. • BLYP-D3/SDD method is the most accurate method for homolytic cleavage of C Sn bond. Abstract Stille coupling is a well-known cross coupling reaction, where the rate determination step is the dissociation of carbon stannous (C Sn) bond. The organotin compounds are also used as precursors in the manufacturing of tin oxide films, solar cells, gas sensors, flat panel display technology and low emission glass materials, etc. The reactivity of organotin compounds has direct relationship with the homolytic cleavage of C Sn bond. Therefore, accurate determination of C Sn bond has direct relevance in understanding many phenomena. The current benchmark study is aimed at finding out the accurate theoretical method for the homolytic cleavage (bond dissociation energy) of C Sn bond. In this regard, nineteen DFs from eight different classes of DFT with two effective core potential basis sets (LANL2DZ and SDD) and two Karlsruhe basis sets (def2-SVP and def2-TZVP) are selected for the BDE calculation of C Sn bond. Ten structurally diverse organotin compounds with experimentally known BDE of C Sn bond are selected from the literature. The statistical [root mean square deviation (RMSD), standard deviation (SD), Pearson’s correlation (R) and mean absolute error (MAE)] results are obtained by the comparison of theoretical data with the experimental BDE values of C Sn bond of selected organotin compounds. Among all DFT classes, GGA-D class is a batter class and BLYP-D3 functional of this class is selected as the best functional for homolytic bond dissociation energy (BDE) calculation of C Sn bond. This functional with SDD basis set shows remarkable performance in reproducing the BDE of C Sn bond with more accuracy. The SD, RMSD, R and MAE are 4.11 kcal mol−1 is 3.9 kcal mol−1 is 0.963 and −0.01 kcal mol−1, respectively. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations of structures and bonding in the transition metal complexes with silylone ligands [Mo(CO) 5 -Si(XCp ∗ ) 2 ] ( Mo5-SiX ) (X = B–Tl) are reported at the BP86 level of theory with various basis sets SVP, TZVPP, TZ2P + . The calculated equilibrium structures of complexes show that the silylone ligands Si(XCp ∗ ) 2 are bonded in a tilted orientation to the metal fragment Mo(CO) 5 in Mo5-SiX . The bond dissociation energies (BDEs) increase from the weakest bonded boron complex, Mo5-SiB , to the strongest bonded thallium adduct, Mo5-SiTl . The bonding analysis suggests that the trend of the Mo Si bond strength in complexes comes from the increase of (CO) 5 Mo ← Si(XCp ∗ ) 2 donation and the increase of the electrostatic interaction Δ E elstat . [ABSTRACT FROM AUTHOR]

A benchmark study of Bond Dissociation Energies (BDEs) of various chemical bonds is carried out by Density Functional theory (DFT) method. The aim of the present research study was to find out the best suited functional and basis set to calculate BDEs of selected bonds of silicon with halogens (F, Cl, Br), N, H, C and O. Six different functionals (CAM/B3LYP, B3LYP, B3PW91, PBEPBE, TPSSTPSS) were applied on 36 molecules of different nature. Furthermore, six different basis sets 3-21G, aug-cc-pVTZ, 6-31G, aug-cc-pVDZ, DGDZVP and DGDZVP2 were also applied on these molecules with the best suited functional CAM/B3LYP. After rigorous effort it can be safely said that the best basis set for calculating BDEs for Si H, Si C, Si N bonds using CAM-B3LYP functional is 3-21G and for Si-halogens,aug-cc-pVTZ was found to be best basis set. [ABSTRACT FROM AUTHOR]

The effect of external perturbations, namely solvent and external electric field on potential energy surface (PES) and bond dissociation energy of C-X (XF, Cl, Br, N, O) bonds has been studied in the light of density functional theory (DFT). The study reveals that presence of solvent as well as external electric field changes the curvature of the PES significantly. Bond dissociation energy significantly drops in presence of both the external perturbation. Effect of solvent and external electric field on the PES of different C-X bonds has been analyzed using Density Functional Theory. The depth of the PES varies considerably with the polarity of the solvent as well as with the strength of the applied external electric field. Accordingly bond dissociation energy is also affected by the presence of solvent and external electric field. [ABSTRACT FROM AUTHOR]

Ab initio and density functional theory (DFT) calculations are employed to investigate the formation and isomerization pathways of methyl thionitrate, CHSNO, and the S-N bond dissociation energies (BDE) of the sulfonated methyl thionitrates of the type CHS(O)NO ( n = 0, 1, 2). The calculations indicate that CHSNO may be formed as a stabilized by-product in the reaction CHS + NO which mainly leads to CHSO + NO. In general, the compounds of the type CHS(O)NO ( n = 0, 1, 2) may be formed as bound intermediates in the homologous reactions CHS(O) + NO. The calculated S-N BDE exhibit an interesting dependence on the number of the sulfonic oxygen atoms present in each species. [ABSTRACT FROM AUTHOR]

Abstract: The accurate O-H bond dissociation enthalpies for a series of meta and para substituted phenols (X-C6H4-OH, X=H, F, Cl, CH3, OCH3, OH, NH2, CF3, CN, and NO2) have been calculated by using the (RO)B3LYP procedure with 6-311G(d,p) and 6-311++G(2df,2p) basis sets. The proton affinities of the corresponding phenoxide ions (XC6H4-O-) have also been computed at the same level of theory. The effect of change of substituent position on the energetics of substituted phenols has been analyzed. The correlations of Hammett’s substituent constants with the bond dissociation enthalpies of the O-H bonds of phenols and proton affinities of phenoxide ions have been explored.

The characters of high density and high heat of formation of cage molecules have attracted a lot of investigations as potential energetic materials. Several such compounds have been synthesized, e.g., octanitrocubane, hexanitrohexaazaisowurzitane (CL-20), and 4-trinitroethyl-2, 6, 8, 10, 12-pentanitrohexaazaisowurtzitane(TNE-CL-20). In the present study, a new cage compound, namely 2, 4, 6, 8, 10, 12, 13-heptaazatetracyclo [5.5.1.0 3,11.0 5,9] tridecane (HATT), was proposed. Density functional theory has been employed to study the geometric and electronic structures for a series of nitro derivatives of HATT at the B3LYP/6-31G(d,p) level. Thermodynamic properties derived on the basis of statistical thermodynamic principles are linearly correlated with the numbers of nitro group as well as the temperature. Detonation performance was evaluated based on the calculated densities and heats of formation. It is found that some title compounds have high densities of ca. 1.9 g cm −3, detonation velocities over 9.0 km s −1, and detonation pressures of about 40.0 GPa and may be novel potential candidates of high energy density compounds (HEDCs). Thermal stability and pyrolysis mechanism of the nitro HATTs were investigated by calculating the bond dissociation energies ( BDE). In conjunction with the detonation performance and thermal stability, HATTs with no less than five nitro groups are recommended as the preferred candidates of HEDCs. These results provide basic information for the further studies of cage compounds. [ABSTRACT FROM AUTHOR]

Background: The rapid access to intrinsic physicochemical properties of molecules is highly desired for large scale chemical data mining explorations such as mass spectrum prediction in metabolomics, toxicity risk assessment and drug discovery. Large volumes of data are being produced by quantum chemistry calculations, which provide increasing accurate estimations of several properties, e.g. by Density Functional Theory (DFT), but are still too computationally expensive for those large scale uses. This work explores the possibility of using large amounts of data generated by DFT methods for thousands of molecular structures, extracting relevant molecular properties and applying machine learning (ML) algorithms to learn from the data. Once trained, these ML models can be applied to new structures to produce ultra-fast predictions. An approach is presented for homolytic bond dissociation energy (BDE). Results: Machine learning models were trained with a data set of >12,000 BDEs calculated by B3LYP/6-311++G (d,p)//DFTB. Descriptors were designed to encode atom types and connectivity in the 2D topological environment of the bonds. The best model, an Associative Neural Network (ASNN) based on 85 bond descriptors, was able to predict the BDE of 887 bonds in an independent test set (covering a range of 17.67-202.30 kcal/mol) with RMSD of 5.29 kcal/mol, mean absolute deviation of 3.35 kcal/mol, and R2 = 0.953. The predictions were compared with semi-empirical PM6 calculations, and were found to be superior for all types of bonds in the data set, except for O-H, N-H, and N-N bonds. The B3LYP/6-311++G(d,p)//DFTB calculations can approach the higher-level calculations B3LYP/6-311++G(3df,2p)//B3LYP/6-31G(d,p) with an RMSD of 3.04 kcal/mol, which is less than the RMSD of ASNN (against both DFT methods). An experimental web service for on-line prediction of BDEs is available at http://joao. airesdesousa.com/bde. Conclusion: Knowledge could be automatically extracted by machine learning techniques from a data set of calculated BDEs, providing ultra-fast access to accurate estimations of DFT-calculated BDEs. This demonstrates how to extract value from large volumes of data currently being produced by quantum chemistry calculations at an increasing speed mostly without human intervention. In this way, high-level theoretical quantum calculations can be used in large-scale applications that otherwise would not afford the intrinsic computational cost. [ABSTRACT FROM AUTHOR]

DFT calculations, with VWN exchange correlation functional and double numeric basis set, were used to evaluate the energies required for the scission reactions taking place in the initial stage of the thermal degradation of Poly(methyl methacrylate) (PMMA) in the presence of a carbon nanotube (CNT). Side group and main chain scissions were investigated. The results averaged from five configurations of pure PMMA (DP = 5) were used as references and compared to the results obtained for the five same configurations of PMMA grafted on three carbon nanotubes of similar diameter (1.49 nm). The bond dissociation energies (BDE) of main chain scission evaluated for grafted PMMA was 4 % less endothermic than for pure PMMA. These results seemed independent of the tested chirality (11,11); (12,10) and (16,5) of the carbon nanotubes. Comparisons with the BDE of the weakest bonds due to intrinsic defaults (head to head and unsaturated end chain) were performed. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

The performances of the DFT functionals B3LYP, BHandHLYP, M06, M06-2X, PBE1PBE, TPSSh, X3LYP, and BP86 have been benchmarked with a thermochemistry database containing 50 bond dissociation energies (BDEs) of M-OH complexes ( n = 0-2). Among the tested methods, B3LYP was found to perform best both in accuracy and error distributions. Next, 162 BDEs (M-OH) (M = K − La, Hf − Rn; n = 0-2) are calculated at the B3LYP/def2-QZVP level of theory and their periodic trends are presented as an overview. Further, the H-atom affinities of MO and MOH are derived from the calculated BDEs. [ABSTRACT FROM AUTHOR]

Abstract: The ionization potential (IP), O–H bond dissociation energy (BDE) and intra-molecular hydrogen bonding in selected para-substituted salicylic acids, 5-R-SA, with R as –NO2, –CHO, –COOH, -halogen, –OH, –OCH3, -alkyl, –NH2, –NH(CH3), –N(CH3)2 and their radicals have been investigated by density functional theory with B3LYP functional in conjunction with 6-31G(d) and 6-311++G(d,p) basis sets. All the calculations have also been performed using BHLYP functional in conjunction with 6-311++G(d,p) basis set. A common order of IPs and BDEs for the studied 5-R-SAs is found as –NO2 >–COOH (–CHO)>–H>–OCH3 >–NH2 >–NH(CH3)>–N(CH3)2. The effect of substituents on the structure, charge distribution and intra-molecular hydrogen bond has also been discussed. [Copyright &y& Elsevier]

Abstract: The S–NO bond dissociation energies (BDEs) for S-nitrosothiols (RSNO) compounds are computed using the DFT (B3LYP, B3PW91 and B3P86) with the 6-31g∗∗ and 6-311g∗∗ basis set. By comparing the computed energies and experimental results, we find that the B3PW91/6-31g∗∗ and B3P86/6-311g∗∗ method can give good results of BDE, which have the mean absolute deviations of 7.39 and 7.57kJ/mol, respectively. Considering the smaller maximum difference, we recommend the B3PW91 method combined with 6-31g∗∗ basis set, as a satisfactory method of computing the BDEs for removal of the NO group in RSNO compounds. In addition, we find that the mean absolute deviation reduces from 9.07 to 7.39kJ/mol when the 6-311g∗∗ basis set in the B3PW91 model is replaced by 6-31g∗∗ basis set, which proves that B3PW91 DFT method is sensitive to the basis sets. [Copyright &y& Elsevier]