Infrared Intensification and Hydrogen Bond Stabilization: Beyond Point Charges

Autor(es)

Duarte, Leonardo J. ^[1] ; Silva, Arnaldo F. ^[1] ; Richter, Wagner E. ^[2] ; Bruns, Roy E. ^[1]

Afiliação do(s) autor(es)

^[1] Univ Estadual Campinas, Inst Quim, CP 6154, BR-13083970 Campinas, SP - Brazil

^[2] Univ Tecnol Fed Parana, Dept Engn Quim, Campus Ponta Grossa, Av Monteiro Lobato S-N, BR-84016210 Curitiba, Parana - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Physical Chemistry A; v. 123, n. 30, p. 6482-6490, AUG 1 2019.
• Citações Web of Science: 0

Resumo

Infrared band intensification of the A-H bond stretching mode of A-H center dot center dot center dot B acid-base systems has long been known to be the most spectacular spectral change occurring on hydrogen bonding. A QTAIM/CCTDP model is reported here to quantitatively explain the electronic structure origins of intensification and investigate the correlation between experimental enthalpies of formation and infrared hydrogen bond stretching intensifications amply reported in the literature. Augmented correlation-consistent polarized triple-zeta quantum calculations at the MP2 level were performed on complexes with HF and HCl electron acceptors and HF, HCl, NH3, H2O, HCN, acetonitrile, formic acid, acetaldehyde, and formaldehyde electron donor molecules. The A-H stretching band intensities are calculated to be 3 to 40 times larger than their monomer values. Although the acidic hydrogen atomic charge is important for determining the intensities of HF complexes relative to HCl complexes with the same electron donor, they are not important for infrared intensifications occurring on hydrogen bond formation for a series of bases with a common acid. Charge transfers are found to be the most important factor resulting in the intensifications, but dipolar polarization effects are also significant for each series of complexes. A mechanism involving intra-acid and intermolecular electron transfers as well as atomic polarizations is proposed for understanding the intensifications. The calculated sums of the intermolecular electron transfer and acid dipolar polarization contributions to the dipole moment derivatives for each series of complexes are highly correlated with their enthalpies of formation and H-bond intensifications. This could be related to increasing electron transfer from base to acid that correlates with the calculated hydrogen bonding energies and may be a consequence of the A-H bond elongation on complex formation having amplitudes similar to those expected for the A-H vibration. (AU)

• Processo FAPESP: 18/08861-9 - Aplicação do modelo QTAIM / CCTDP e machine learning para a previsão de reatividades químicas
• Beneficiário: Roy Edward Bruns
• Modalidade de apoio: Auxílio à Pesquisa - Regular
• Processo FAPESP: 14/21241-9 - Inclusão de polarização na descrição de aminoácidos e peptídeos utilizando multipolos atômicos calculados a partir de densidades eletrônicas
• Beneficiário: Arnaldo Fernandes da Silva Filho
• Modalidade de apoio: Bolsas no Brasil - Pós-Doutorado
• Processo FAPESP: 17/22741-3 - Uso de multipolos atômicos e desenvolvimento de modelos de machine learning na investigação de estados de transição
• Beneficiário: Leonardo José Duarte
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto