Center for Computational Quantum ChemistryUniversity of GeorgiaAthens

Center for Computational Quantum ChemistryUniversity of GeorgiaAthens


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Anand M.,Center for Computational Quantum ChemistryUniversity of GeorgiaAthens | Schaefer H.F.,Center for Computational Quantum ChemistryUniversity of GeorgiaAthens | Wu J.I.-C.,Center for Computational Quantum ChemistryUniversity of GeorgiaAthens
Journal of Computational Chemistry | Year: 2015

Self-assembling building blocks like the 4-pyridone can exhibit extraordinary H-bond-aromaticity coupling effects. Computed dissected nucleus independent chemical shifts (NICS(1)zz), natural bond orbital (NBO) charges, and energy decomposition analyses (EDA) for a series of hydrogen (H-) bonded 4-pyridone chains (4-py)n (n = 2 to 8) reveal that H-bonding interactions can polarize the 4-pyridone exocyclic C=O bonds and increase 4n+2 π-electron delocalization in the six-membered ring. The resulting H-bonded 4-pyridone units display enhanced π-aromatic character (both magnetically and energetically) and their corresponding N-H···O=C interactions are strengthened. These π-electron polarization effects do not depend on the relative orientations (co-planar or perpendicular) of the neighboring 4-pyridone units, but increase with the number of H-bonded units. © 2015 Wiley Periodicals, Inc.


Li G.,South China Normal UniversityGuangzhou510006 China | Wang H.,Key Laboratory of Theoretical Chemistry of the EnvironmentCenter for Computational Quantum Chemistry | Li Q.-S.,Key Laboratory of Theoretical Chemistry of the EnvironmentCenter for Computational Quantum Chemistry | Xie Y.,Center for Computational Quantum ChemistryUniversity of GeorgiaAthens | Schaefer H.F.,Center for Computational Quantum ChemistryUniversity of GeorgiaAthens
Journal of Computational Chemistry | Year: 2015

The entrance complex, transition state, and exit complex for the bromine atom plus water dimer reaction Br+(H2O)2 → HBr+(H2O)OH and its reverse reaction have been investigated using the CCSD(T) method with correlation consistent basis sets up to cc-pVQZ-PP. Based on the CCSD(T)/cc-pVQZ-PP results, the reaction is endothermic by 31.7 kcal/mol. The entrance complex Br. . .(H2O)2 is found to lie 6.5 kcal/mol below the separated reactants. The classical barrier lies 28.3 kcal/mol above the reactants. The exit complex HBr. . .(H2O)OH is bound by 6.0 kcal/mol relative to the separated products. Compared with the corresponding water monomer reaction Br+H2O → HBr+OH, the second water molecule lowers the relative energies of the entrance complex, transition state, and exit complex by 3.0, 3.8, and 3.7 kcal/mol, respectively. Both zero-point vibrational energies and spin-orbit coupling effects make significant changes to the above classical energetics. Including both effects, the predicted energies relation to separated Br+(H2O)2 are -3.0 kcal/mol [Br···(H2O)2], 28.2 kcal/mol [transition state], 26.4 kcal/mol [HBr···(H2O)OH], and 30.5 kcal/mol [separated HBr+(H2O)OH]. The potential energy surface for the Br+(H2O)2 reaction is related to that for the valence isoelectronic Cl+(H2O)2 system but radically different from the F+(H2O)2 system. © 2015 Wiley Periodicals, Inc.

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