Benchmark calculations for bond dissociation energies and enthalpy of formation of chlorinated and brominated polycyclic aromatic hydrocarbons

Abstract

Benchmark calculations using state-of-the-art DFT functionals and composite methods for bond dissociation energy and enthalpy of formation of halogenated polycyclic aromatic hydrocarbons are performed.

Formation of negative ions from cobalt tricarbonyl nitrosyl Co(CO)3NO clusters

“…However, saving the This journal is © the Owner Societies 2024 computer time decreases the accuracy of the method compared to other composite approaches. Benchmark studies predicted for the calculated enthalpies of formation exhibit the averaged mean unsigned deviations of B1.5 kcal mol À1 (estimated for several tens of C x H y O z molecules 66 ) or even up to B3 kcal mol À1 (estimated for several tens of chlorinated/brominated compounds 67 ) with respect to experimental values. With considerably lower computational costs, the CBS-QB3 enthalpies of formation are comparable with the most accurate ones derived from the G4 approach.…”

“…The CBS-QB3 method offers one of the lowest computational costs compared with other composite approaches in GAUSSIAN developed to achieve very accurate energies, such as G3, 61 G3MP2, 62 G4, 63 CBS-APNO, 64 and W1BD. 65 Thus, the CBS-QB3 method can be several units, tens or even hundreds times faster when applied to different organic compounds 66,67 and can be used for transition metal complexes contrary to some of the other composite methods mentioned above. However, saving the computer time decreases the accuracy of the method compared to other composite approaches.…”

“…With considerably lower computational costs, the CBS-QB3 enthalpies of formation are comparable with the most accurate ones derived from the G4 approach. 67 However, poorer accuracy of CBS-QB3 is declared for relative energies such as BDEs calculated for organic brominated and chlorinated compounds, with an averaged mean unsigned deviation above 6 kcal mol À1 , 67 or reaction barrier heights (of 26 pericyclic reactions) with a mean absolute deviation of 2.1 kcal mol À1 (contrary to 0.6 kcal mol À1 of G4, or 0.2 kcal mol À1 of most accurate CCSD(T)/CBS(MPn) approaches used 68 ). Heats of formation calculated for transition metal complexes can be achieved with the best accuracy by Wilson's ccCA-TM composite method developed for transition metals, 69,70 with a mean absolute deviation of B3 kcal mol À1 , including MP2/cc-pVxZ CBS extrapolation followed by high level CCSD(T).…”

In Vitro Evaluation and In Silico Calculations of the Antioxidant and Anti-Inflammatory Properties of Secondary Metabolites from Leonurus sibiricus L. Root Extracts

“…The BDE values were obtained based on density functional theory calculations (DFTs). A number of theoretical studies indicate that BDE is strongly dependent on the method used, especially the basis set [ 53 , 54 , 55 , 56 , 57 ]. In a work [ 43 ], the most accurate values of BDE were obtained from the two methods: B3LYP/6-311++G(2d,2p) and B3LYP/6-311++G(d,p), which contain the hybrid functional B3LYP [ 58 ] and People’s triple-zeta basis set.…”

Expansion of bond dissociation prediction with machine learning to medicinally and environmentally relevant chemical space

“…M06-2X/def2-TZVP enthalpies (including the unscaled ZPE) and RRHO Gibbs energies (1 atm, 298 K) were computed: the accuracy of this level of theory for halogenated molecules has been benchmarked, showing that hybrid functionals with a high proportion of exact exchange or long-range corrections are more accurate. [27][28][29][30] An automated workow generated the structures of parent and radical fragments from SMILES inputs by enumerating all possible exocyclic single-bond dissociations. Following conformational analysis with RDKit, the most stable conformers were optimized with DFT (further details in Section 1 ESI †).…”