An atom in molecules study of infrared intensity enhancements in fundamental donor stretching bands in hydrogen bond formation

作者：Terrabuio Luiz A; Richter Wagner E; Silva Arnaldo F; Bruns Roy E; Haiduke Roberto L A^*

来源：Physical Chemistry Chemical Physics, 2014, 16(45): 24920-24928.

DOI：10.1039/c4cp03489a

Vibrational modes ascribed to the stretching of X-H bonds from donor monomers (HXdonor) in complexes presenting hydrogen bonds (HF center dot center dot center dot HF, HCl center dot center dot center dot HCl, HCN center dot center dot center dot HCN, HNC center dot center dot center dot HNC, HCN center dot center dot center dot HF, HF center dot center dot center dot HCl and H2O center dot center dot center dot HF) exhibit large (4 to 7 times) infrared intensity increments during complexation according to CCSD/cc-pVQZ-mod calculations. These intensity increases are explained by the charge-charge fluxdipole flux (CCFDF) model based on multipoles from the Quantum Theory of Atoms in Molecules (QTAIM) as resulting from a reinforcing interaction between two contributions to the dipole moment derivatives with respect to the vibrational displacements: charge and charge flux. As such, variations that occur in their intensity cross terms in hydrogen bond formation correlate nicely with the intensity enhancements. These stretching modes of HXdonor bonds can be approximately modeled by sole displacement of the positively charged hydrogens towards the acceptor terminal atom with concomitant electronic charge transfers in the opposite direction that are larger than those occurring for the H atom displacements of their isolated donor molecules. This analysis indicates that the charge-charge flux interaction reinforcement on H-bond complexation is associated with variations of atomic charge fluxes in both parent molecules and small electronic charge transfers between them. The QTAIM/CCFDF model also indicates that atomic dipole flux contributions do not play a significant role in these intensity enhancements.

• 出版日期2014