Are resonance-assisted hydrogen bonds ‘resonance assisted’? A theoretical NMR study

The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspective

“…Such a reduction is of course accompanied by a concomitant increase in the total number of localised electrons, and becomes a powerful argument against the traditional role assigned to resonance in RAHBs, in agreement with previous experimental and theoretical studies which found no indication of an increased electron delocalisation in these types of H-bonds. [29][30][31][32][33][36][37][38][39][40] Since, as stated above, the interacting quantum atom partition provides a unique combination of electron and energy descriptors, we may now explore the energy features of the formation of the HB associated with the previously discussed changes in R(r) and R 2 (r 1 ,r 2 ). Following the previous line of reasoning, we first examine the energetics of resonance and bond order equalization, which are indicated in terms of the covalent, i.e.…”

“…For example, the substitution of electron donating and withdrawing groups in the system does not affect the energetics of different RAHBs. 29 Likewise, the analysis of the NMR properties of systems containing RAHBs developed by Alkorta and coworkers 30,31 showed that neither the proton chemical shifts nor the coupling constants point out to significant contributions from p-resonance to these interactions. On the contrary, it is put forward that the reason behind the RAHB strengthening lies in the s-skeleton of the system.…”

Reinvestigation of intramolecular hydrogen bond in malonaldehyde derivatives: An ab initio, AIM and NBO study

“…When the proton donor and acceptor are connected by a conjugated framework, a resonance assisted hydrogen bond (RAHB) is introduced. As Gilli et al [3] announced this concept, it has become one of the most frequently used words in structural chemistry, and however, it has become the subject of various challenges by Elgureo and coworkers [4][5][6][7]. The RAHB systems belong to the strong hydrogen bond interactions and thus lead to significant change in geometrical parameters, vibrational frequencies, and electronic energy of the molecules.…”

Cooperative and anticooperative effects in resonance assisted hydrogen bonds in merged structures of malondialdehyde

“…[9] Figure 2 (a) shows this interaction between the hydrogen bond and the π system within malondialdehyde, CHO−CH − − CH−OH. Resonance assisted hydrogen bonds have been of considerable interest in physical chemistry, a situation which has lead to numerous theoretical [10][11][12] and experimental [13,14] reports concerned with the nature of these HBs. In addition, the RAHB concept has been used to better understand intermolecular interactions in relevan systems in chemistry and biology, like those present in DNA [15][16][17] and proteins [3] .…”