“…Fifth, the spin-component scaled variant of MP2 demonstrates poor accuracy in the calculated DE value for the cc-1b, which results in the wrong ordering of the cc-and tt-conformers. On the other hand, SCS-MP2 shows an improvement in DE for 1a over MP2, which in turn is in line with previous reports on the improved performance of SCS-MP2 in providing the structural and energetic description of conformations for molecules [50,51] and molecular complexes [52][53][54].…”
The conformational behavior of ten diheteroaryl ketones and thioketones is investigated using various quantum chemical methods. These ketones and thioketones are formed by the disubstitution of formaldehyde and thioformaldehyde with such a heteroaryl group as 2-furanyl, 2-thiophenyl, 2-selenophenyl, 2-pyrrolyl or 1-methyl-2-pyrrolyl. For these compounds, their conformational preference and the energetic ordering of their conformers are determined at the MP2 and B3LYP levels of theory. Energetic barriers resulting from the interconversion between conformations are also estimated. The natural bond orbital (NBO) and interacting quantum atoms (IQA) methods are used to study fundamental intramolecular energetic effects influencing the stability of individual conformers. The results of the two methods indicate the great significance of the effect associated with electron delocalization (in the form of either NBO donor-acceptor interactions or the IQA interatomic exchange-correlation interaction energy) in governing the conformational behavior of the investigated diheteroaryl ketones and thioketones.
“…Fifth, the spin-component scaled variant of MP2 demonstrates poor accuracy in the calculated DE value for the cc-1b, which results in the wrong ordering of the cc-and tt-conformers. On the other hand, SCS-MP2 shows an improvement in DE for 1a over MP2, which in turn is in line with previous reports on the improved performance of SCS-MP2 in providing the structural and energetic description of conformations for molecules [50,51] and molecular complexes [52][53][54].…”
The conformational behavior of ten diheteroaryl ketones and thioketones is investigated using various quantum chemical methods. These ketones and thioketones are formed by the disubstitution of formaldehyde and thioformaldehyde with such a heteroaryl group as 2-furanyl, 2-thiophenyl, 2-selenophenyl, 2-pyrrolyl or 1-methyl-2-pyrrolyl. For these compounds, their conformational preference and the energetic ordering of their conformers are determined at the MP2 and B3LYP levels of theory. Energetic barriers resulting from the interconversion between conformations are also estimated. The natural bond orbital (NBO) and interacting quantum atoms (IQA) methods are used to study fundamental intramolecular energetic effects influencing the stability of individual conformers. The results of the two methods indicate the great significance of the effect associated with electron delocalization (in the form of either NBO donor-acceptor interactions or the IQA interatomic exchange-correlation interaction energy) in governing the conformational behavior of the investigated diheteroaryl ketones and thioketones.
“…Overall, the performance of the DFT methods in reproducing the structures of SnH 2 -benzene and SnH 2 -pyridine turns out to be transferable to our more representative set of the complexes of simple stannylenes with aromatic molecules. From the current results and from what we have recently demonstrated for trimethyltin cyanide dimer [ 91 ], it can be deduced that the ωB97X and M11 density functionals generally show excellent performance in predicting structures of systems with weak interactions involving tin. Fig.…”
The performances of Møller-Plesset second-order perturbation theory (MP2) and density functional theory (DFT) have been assessed for the purposes of investigating the interaction between stannylenes and aromatic molecules. The complexes between SnX2 (where X = H, F, Cl, Br, and I) and benzene or pyridine are considered. Structural and energetic properties of such complexes are calculated using six MP2-type and 14 DFT methods. The assessment of the above-mentioned methods is based on the comparison of the structures and interaction energies predicted by these methods with reference computational data. A very detailed analysis of the performances of the MP2-type and DFT methods is carried out for two complexes, namely SnH2-benzene and SnH2-pyridine. Of the MP2-type methods, the reference structure of SnH2-benzene is reproduced best by SOS-MP2, whereas SCS-MP2 is capable of mimicking the reference structure of SnH2-pyridine with the greatest accuracy. The latter method performs best in predicting the interaction energy between SnH2 and benzene or pyridine. Among the DFT methods, ωB97X provides the structures and interaction energies of the SnH2-benzene and SnH2-pyridine complexes with good accuracy. However, this density functional is not as effective in reproducing the reference data for the two complexes as the best performing MP2-type methods. Next, the DFT methods are evaluated using the full test set of SnX2-benzene and SnX2-pyridine complexes. It is found that the range-separated hybrid or dispersion-corrected density functionals should be used for describing the interaction in such complexes with reasonable accuracy.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-015-2589-1) contains supplementary material, which is available to authorized users.
“…More recent DFT generations, represented in Table 2 by M06-2X and ωB97X, produce the E int energies that mirror the CCSD(T)/CBS results fairly closely. It is known that the ωB97X functional has proved to be highly successful at providing accurate bond energies for compounds containing transition metals [ 62 ], as well as interaction energies for complexes of Sn(II) [ 19 ] and Sn(IV) [ 63 , 64 ]. The good performance of M06-2X in predicting the E int energies of 1 – 5 seems to confirm the important role of medium-range electron correlation for these complexes [ 30 , 65 ].…”
For a series of five model complexes composed of a singlet SnX2 molecule (X = H, F, Cl, Br, I) and a benzene molecule, the first-principles calculations of their energetics and the analysis of their electron density topology have been performed. The CCSD(T)/CBS interaction energy between SnX2 and C6H6 fall into the range between −10.0 and −11.2 kcal/mol, which indicates that the complexes are rather weakly bound. The relevant role of electrostatic and dispersion contributions to the interaction energy between SnX2 and C6H6 is highlighted in the results obtained from the symmetry-adapted perturbation theory (SAPT). The electron density topological analysis has been carried out using the quantum theory of atoms in molecules (QTAIM) and the noncovalent interactions (NCI) visualization index. Both QTAIM and NCI prove the closed-shell, noncovalent and attractive character of the interaction. A very small charge transfer from C6H6 to SnX2 has been detected. The formation of the five complexes is accompanied by the electron density deformations that are spatially restricted mostly to the region around the Sn atom and its adjacent C atom. The results presented in this work shed some light on the nature of the interactions associated with crystalline structural motifs involving low-valent tin complexed with neutral aryl rings.Electronic supplementary materialThe online version of this article (doi:10.1007/s00894-016-3053-6) contains supplementary material, which is available to authorized users.
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