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Relacja pomiędzy wiązaniem wodorowym wspomaganym rezonansem a aromatycznością

Palusiak M.

Wiadomości Chemiczne

2010

[Z] 64, 3-4

263-283

Among the so called non-covalent interactions the hydrogen bond (H-bond) is probably the most frequently and the most thoroughly investigated. This is due to the fact that H-bond plays an essential role in many physical, chemical and biochemical processes. The strongest H-bonds are those assisted with additional effects, as for instance the resonance assisted H-bonds (RAHBs). The concept of RAHB was first proposed by Gilli and co-workers in 1989, and with the time it has become one of the most thoroughly investigated aspects from the field of structural chemistry. Originally, the definition of RAHB was directly connected with the resonance effect acting in RAHB motif (either intra- or intermolecular). Many scientists were exploring the phenomena of the RAHB. Thus, some controversies appeared in connection with the extra stabilization of the RAHB if comparing with its "non-resonance-assisted" counterparts. Some authors criticized the original explanation introduced by Gilli et al. and proposed alternative mechanism responsible for the relatively stronger H-bonding in the RAHB motifs. Since the resonance effect accompanying the formation of H-bridge in RAHBs is in fact a π-electron effect, it may interact with other π -electron effects acting in specific molecules, e.g. with substituent effect or aromatic đ -electron delocalization. In this way the mutual interaction between different đ -electron effects may occur, which may influence many physical and chemical properties of molecular systems under consideration, as for instance the strength of RAHB, local aromaticity, proton transfer barrier and many others. In this paper a short review on the current state of knowledge on RAHB will be presented. The special attention will be paid onto the interrelation between RAHB and local aromaticity in derivatives of polycyclic aromatic hydrocarbons.