Infrared intensities and charge mobility in hydrogen bonded complexes

Abstract

The analytical model for the study of charge mobility in the molecules presented by Galimberti et al. [J. Chem. Phys. 138, 164115 (2013)] is applied to hydrogen bonded planar dimers. Atomic charges and charge fluxes are obtained from density functional theory computed atomic polar tensors and related first derivatives, thus providing an interpretation of the IR intensity enhancement of the X-H stretching band observed upon aggregation. Our results show that both principal and non-principal charge fluxes have an important role for the rationalization of the spectral behavior; moreover, they demonstrate that the modulation of the charge distribution during vibrational motions of the -XH⋯Y- fragment is not localized exclusively on the atoms directly involved in hydrogen bonding. With these premises we made some correlations between IR intensities, interaction energies, and charge fluxes. The model was tested on small dimers and subsequently to the bigger one cytosine-guanine. Thus, the model can be applied to complex systems.

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

“…QTAIM values (Table S2, ESI †) also point to small electronic charge transfers from acceptor to donor units occurring in hydrogen bond formation, which varies between 0.004 and 0.030 e. NBO analyses and the ECCF model also confirm that hydrogen bonding is accompanied by an electronic charge transfer from acceptor to donor molecules. 26,52 These charge changes predicted by QTAIM are in line with the molecular dipole moment strengthening that was observed upon dimerization.…”

Transparent sunlight conversion film based on carboxymethyl cellulose and carbon dots

“…However, the probability of energy transition is dependent on the properties of functional groups. As for a specific functional group, the intensity of infrared absorption band is relative to hydrogen bonds, conjugate groups, Fermi resonance and solvent effect (Galimberti et al, 2013). Besides, concentration of functional groups also has an influence on the intensity of vibration bands.…”

Infrared intensity analysis of hydroxyl stretching modes in carboxylic acid dimers by means of the charge–charge flux–dipole flux model

“…Thus, although there are some theoretical studies regarding the variations of infrared intensities for the XH stretching modes of simple dimers, along with investigations dealing with the perturbation caused by hydrogen bonds in molecular polarizabilities of amino acids and the cooperative effects of these interactions on water clusters, the study of charge redistributions during the formation of more complicated dimers is still scarce. For example, bidentate dimers (HCOOH…HCOOH, FCOOH…FCOOH, among others), which can be bonded by two HBs between hydroxyl and carbonyl groups (O…H), have not yet been subjected to infrared intensity variation investigations via the CCFDF/QTAIM model, although they were analyzed by the equilibrium charges charge flux (ECCF) model, which does not include terms to deal explicitly with the variations in atomic polarizabilities …”

“…For example, bidentate dimers (HCOOH…HCOOH, FCOOH…FCOOH, among others), which can be bonded by two HBs between hydroxyl and carbonyl groups (O…H), have not yet been subjected to infrared intensity variation investigations via the CCFDF/QTAIM model, although they were analyzed by the equilibrium charges charge flux (ECCF) model, which does not include terms to deal explicitly with the variations in atomic polarizabilities. [24] Therefore, we intend to apply the CCFDF/QTAIM partition model to understand the nature of variations in infrared intensities during the dimerization of carboxylic acids in order to propose physical interpretations that rationalize these changes during molecular vibrations. In addition, we used the QTAIM formalism to decompose the electronic energy in intraatomic and interatomic contributions, according to the Interacting Quantum Atom (IQA) proposal, [25,26] in order to investigate the stabilization/destabilization of HBs and hydroxyl (O H) bonds within these carboxylic acid monomers and dimers.…”