Tuning the strength of the resonance-assisted hydrogen bond in acenes and phenacenes with two o-hydroxyaldehyde groups: the importance of topology
The fact that intramolecular resonance-assisted hydrogen bonds (RAHBs) are stronger than conventional ones is attributed to the partial delocalization of the pi-electrons within the hydrogen bond (HB) motif, the so-called quasi-ring. If an aromatic ring is involved in the formation of the RAHB, prev...
| Authors: | , , , , |
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| Format: | article |
| Status: | Versión aceptada para publicación |
| Publication Date: | 2019 |
| Country: | España |
| Institution: | Varias* (Consorci de Biblioteques Universitáries de Catalunya, Centre de Serveis Científics i Acadèmics de Catalunya) |
| Repository: | Recercat. Dipósit de la Recerca de Catalunya |
| OAI Identifier: | oai:recercat.cat:10256/17383 |
| Online Access: | http://hdl.handle.net/10256/17383 |
| Access Level: | Open access |
| Keyword: | Enllaços d'hidrogen Hydrogen bonding Aromaticitat (Química) Aromaticity (Chemistry) Funcional de densitat, Teoria del Density functionals |
| Summary: | The fact that intramolecular resonance-assisted hydrogen bonds (RAHBs) are stronger than conventional ones is attributed to the partial delocalization of the pi-electrons within the hydrogen bond (HB) motif, the so-called quasi-ring. If an aromatic ring is involved in the formation of the RAHB, previous studies have shown that there is an interplay between aromaticity and HB strength. Moreover, in 1,3-dihydroxyaryl-2-aldehydes, some of us found that the position of the quasi-ring formed by the substituents interacting through RAHB influences the strength of the H-bonding, the HBs being stronger when a kinked-like structure is generated by formation of the quasi-ring. In this work, we explore this concept further by considering a set of acenes and phenacenes of different sizes with two o-hydroxyaldehyde substituents. Calculations with the CAM-B3LYP/6-311+G(d,p)+GD3B method show that for long acenes or phenacenes, once the substituent effect loses importance because quasi-rings are pull apart far from each other, the different topologies rule the HB distances. This fact can be explained in most cases using an extended Clar's aromatic pi-sextet model. In some kinked systems, however, the justification from the Clar model has to be complemented by taking into account the repulsion between hydrogen atoms. Triphenylene-like compounds with different number of benzene rings have been studied finding out a very good relationship between aromaticity of the ipso- and quasi-rings with the RAHB distances. This result confirms the importance of the communication of the pi-systems of the ipso- and quasi-rings |
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