Interactions between haloperfluorobenzenes and fluoranthene in luminescent cocrystals from π-hole⋯π to σ-hole⋯π bonds

There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

Abstract

From π-hole⋯π to σ-hole⋯π bonds between haloperfluorobenzenes and fluoranthene in luminescent cocrystals.

Abstract

Although there are a number of literature reports in the field of crystal design by σ-hole⋯π or π-hole⋯π bond, there are still very few discussions about under what conditions it is easier to form a σ-hole⋯π bond and under what conditions it is easier to form a π-hole⋯π bond. In order to explore this issue, nine cocrystals were assembled using haloperfluorobenzenes (Cl, Br, I) as the σ-/π-hole bonding donors with fluoranthene (FA) as the bonding acceptor. Single-crystal X-ray diffraction (XRD) analysis reveals that a π-hole⋯π bond occurred in all cocrystals, while both σ-hole⋯π and π-hole⋯π bonds existed in 14DIPB/135TIPB/12DIPB–FA cocrystals. The main bonding patterns of the cocrystals change from π-hole⋯π to additional σ-hole⋯π bonds in the order of the halogen atoms Cl and Br to I. Besides, based on the computational chemistry and the XRD analysis, it is proposed that it is very likely that cocrystals are assembled by both σ-hole⋯π and π-hole⋯π bonding when the σ-hole MEP is much more positive than the π-hole MEP by about 65 kJ mol ⁻¹, and by π-hole⋯π bonding when the MEP of the σ-hole is comparable with that of the π-hole. In addition, the geometric factor in terms of both ring thickness and diameter may play an important part in affecting the bonding pattern. Finally, due to the different interaction patterns and heavy atom perturbing sources, FA in the cocrystals displays different luminescent behaviors.

Related collections

Most cited references 49

Record: found
Abstract: found
Article: not found

Halogen bonding and other σ-hole interactions: a perspective.

Peter Politzer, Jane S Murray, Timothy Clark (2013)

A σ-hole bond is a noncovalent interaction between a covalently-bonded atom of Groups IV-VII and a negative site, e.g. a lone pair of a Lewis base or an anion. It involves a region of positive electrostatic potential, labeled a σ-hole, on the extension of one of the covalent bonds to the atom. The σ-hole is due to the anisotropy of the atom's charge distribution. Halogen bonding is a subset of σ-hole interactions. Their features and properties can be fully explained in terms of electrostatics and polarization plus dispersion. The strengths of the interactions generally correlate well with the magnitudes of the positive and negative electrostatic potentials of the σ-hole and the negative site. In certain instances, however, polarizabilities must be taken into account explicitly, as the polarization of the negative site reaches a level that can be viewed as a degree of dative sharing (coordinate covalence). In the gas phase, σ-hole interactions with neutral bases are often thermodynamically unfavorable due to the relatively large entropy loss upon complex formation.

0 comments Cited 304 times – based on 0 reviews      Review now

Bookmark

Record: found
Abstract: found
Article: not found

Σ-holes, π-holes and electrostatically-driven interactions.

Jane S Murray, Pat Lane, Timothy Clark … (2012)

A positive π-hole is a region of positive electrostatic potential that is perpendicular to a portion of a molecular framework. It is the counterpart of a σ-hole, which is along the extension of a covalent bond to an atom. Both σ-holes and π-holes become more positive (a) in going from the lighter to the heavier atoms in a given Group of the periodic table, and (b) as the remainder of the molecule is more electron-withdrawing. Positive σ- and π-holes can interact in a highly directional manner with negative sites, e.g., the lone pairs of Lewis bases. In this work, the complexes of 13 π-hole-containing molecules with the nitrogen lone pairs of HCN and NH(3) have been characterized computationally using the MP2, M06-2X and B3PW91 procedures. While the electrostatic interaction is a major driving force in π-hole bonding, a gradation is found from weakly noncovalent to considerably stronger with possible indications of some degree of coordinate covalency.