σ-Hole⋯π and lone pair⋯π interactions in benzylic halides

Abstract

Intermolecular and intramolecular halogen···π interactions in benzylic halides (Ph-CR2-X; X = F, Cl, Br and I) derived from 7-phenylnorbornane were investigated. The imposed geometry of the 7-arylnorbornane moiety prevents the participation of intramolecular attractive interactions between the σ-hole region of the halogen atom and the π electrons of the aromatic ring. Crystallographic data show intermolecular halogen bonds in iodide 1 and bromide 2 in the solid state. On the other hand, both UV-Vis and D-NMR data suggest the occurrence of intramolecular interactions between the halogen atoms and the phenyl rings in these compounds in solution. To provide more insight into the nature of the observed stabilizing interactions, density functional calculations were also carried out. These computations confirm the presence of genuine lone pairπ intramolecular interactions which strongly affect the stability and the electronic structure of these species.

Adenine as a Halogen Bond Acceptor: A Combined Experimental and DFT Study

“…It is worth mentioning that in addition to the π-π stacking interactions involving the adenine moieties (see Figure 4, left), lp-π interactions are also established between the negative belt of the iodine atom and the π-system of N 9 -ethyladenine (see Figure 4, right). This type of X···π interaction where the negative belt of the halogen interacts with an acidic π-system has been previously described and discussed in the literature [34,35]. The I···π interaction is represented in Figure 4 as green dotted lines.…”

The σ and π Holes. The Halogen and Tetrel Bondings: Their Nature, Importance and Chemical, Biological and Medicinal Implications

“…[21] Now, great efforts are being done on theoretical studies to better understand the fundamental backgrounds of this type of bonding and, also, on the study of the potential of these interactions and their applications in a wide variety of areas, like materials science, [22] biomedicine or drug design and optimization. [23] Moreover, it is possible to find applications in organic synthesis, organocatalysis, [24] and also in the study of the stereochemistry and conformational stability of halogenated molecules, [25] specially of biomolecules. [26] There are interesting works about the use of halogen bonding as a substitute of hydrogen bonding for the design and development of liquid crystals.…”

Structural, spectroscopic and computational study of 5‐(substituted phenylazo)‐3‐cyano‐1‐ethyl‐6‐hydroxy‐4‐methyl‐2‐pyridones

“…Interactions that involve aromatic rings include p-p stacking, CH-p, and cation-p interactions [18]. The lp-p stacking interactions involve an electrondeficient aromatic ring and a lone pair of neutral electronrich molecules, which have been thoroughly studied both theoretically and experimentally [19][20][21][22][23][24][25][26]. The lp-p stacking interactions involve an electrondeficient aromatic ring and a lone pair of neutral electronrich molecules, which have been thoroughly studied both theoretically and experimentally [19][20][21][22][23][24][25][26].…”

“…In the last decade, anion-p and lone pair-p (lp-p) interactions have gained significant attention in supramolecular packing of organic crystals [19][20][21][22]. They have been primarily recognised in biomolecules such as DNA, RNA and proteins [23], while lp-p interactions have been shown to be present in large numbers in the crystal structures of small organic compounds [20,[24][25][26]. They have been primarily recognised in biomolecules such as DNA, RNA and proteins [23], while lp-p interactions have been shown to be present in large numbers in the crystal structures of small organic compounds [20,[24][25][26].…”

“…In the last decade, anion-p and lone pair-p (lp-p) interactions have gained significant attention in supramolecular packing of organic crystals [19][20][21][22]. The lp-p stacking interactions involve an electrondeficient aromatic ring and a lone pair of neutral electronrich molecules, which have been thoroughly studied both theoretically and experimentally [19][20][21][22][23][24][25][26]. They have been primarily recognised in biomolecules such as DNA, RNA and proteins [23], while lp-p interactions have been shown to be present in large numbers in the crystal structures of small organic compounds [20,[24][25][26].…”