Arrangement of σ-Holes at Halogen Atom in Halonium Cation

Physical Chemistry Chemical Physics, Journal Year: 2025, Volume and Issue: unknown

Published: Jan. 1, 2025

The number of σ-holes in halonium cations depends on the value C–I–C angle.

Language: Английский

---

Competition Between the Two σ‐Holes in the Formation of a Chalcogen Bond

ChemPhysChem, Journal Year: 2023, Volume and Issue: 24(9)

Published: Feb. 6, 2023

A chalcogen atom Y contains two separate σ-holes when in a R1 YR2 molecular bonding pattern. Quantum chemical calculations consider competition between these to engage bond (ChB) with NH3 base. R groups considered include F, Br, I, and tert-butyl (tBu). Also examined is the situation where lies within chalcogenazole ring, its neighbors are C N. Both electron-withdrawing substituents R2 act cooperatively deepen σ-holes, but deeper of holes consistently opposite more group, also favored form stronger ChB. The formation simultaneous ChBs triad requires as double electron acceptor, so anti-cooperativity weakens each relative simple dyad. This effect such that some shallower unable ChB at all base occupies other site.

Language: Английский

---

Does a halogen bond require positive potential on the acid and negative potential on the base?

Physical Chemistry Chemical Physics, Journal Year: 2023, Volume and Issue: 25(10), P. 7184 - 7194

Published: Jan. 1, 2023

It is usually expected that formation of a halogen bond (XB) requires region positive electrostatic potential associated with σ or π-hole on the Lewis acid will interact negative base, either lone pair π-bond region. Quantum calculations model systems suggest this not to be necessary. The placement electron-withdrawing substituents base can reverse sign in its positive, and nonetheless engage XB σ-hole acid. scenario also possible certain circumstances, as negatively charged form base. Despite these classical Coulombic repulsions, overall interaction attractive XBs, albeit only weakly so. strengths bonds are surprisingly insensitive changes partner molecule. For example, even wide range depth approaching yields minimal change strength potential.

Language: Английский

---

Influence of the Coinage Metal(111) Surface on the Orientation of the σ Hole and the Halogen Bonding Strength of Bromo/Iodobenzene

The Journal of Physical Chemistry C, Journal Year: 2024, Volume and Issue: 128(14), P. 5848 - 5859

Published: March 12, 2024

The halogen bonding concept is well established and states that the strength of bond increases with polarizability halogen. Recent experimental studies aromatics halogenated bromine iodine on Cu(111) surface showed known order Br < I can be reversed to > I. To understand this reversal effect in more detail, we performed model calculations bromo/iodobenzene (111) coinage metal surfaces (Cu, Ag, Au) using density functional theory. We characterized as gas phase. In addition, investigated influence inclination σ holes. study shows an hole iodobenzene contrast bromobenzene. This occurs almost exclusively only slightly present Ag(111), while it does not occur Au(111). Furthermore, found tilt independent adsorption position (top, bridge, fcc, hcp hollow site). As a result tilting hole, weakened, leading inversion strength. Thus, I, contrary well-known trend, whereas Ag(111) Au(111), Br, line trend.

Language: Английский

---

Adjusting the balance between hydrogen and chalcogen bonds

Physical Chemistry Chemical Physics, Journal Year: 2022, Volume and Issue: 24(47), P. 28944 - 28955

Published: Jan. 1, 2022

A complex is assembled which pairs a carboxyl group of X1COOH with 1,2,5-chalcogenadiazole ring containing substituents on its C atoms. The OH the donates proton to N atom form OH⋯N H-bond (HB), while carbonyl O engages in Y⋯O chalcogen bond (ChB) Y = S, Se, Te. ChB strengthened by enlarging size from S Se Placement an electron-withdrawing (EWG) X1 acid strengthens HB weakening ChB; reverse occurs when EWGs are placed ring. By selection proper two units, it possible achieve near perfect balance between strengths these bonds. These also reflected NMR spectroscopic properties chemical shielding various atoms and coupling nuclei directly involved each bond.

Language: Английский

---

Quantum chemical analysis of noncovalent bonds within crystals. Concepts and concerns

CrystEngComm, Journal Year: 2023, Volume and Issue: 25(36), P. 5060 - 5071

Published: Jan. 1, 2023

The quantum chemical calculation of the strength a primary noncovalent bond within crystal must navigate numerous complicating issues. Choice geometry, polarizing effects substituents, and delocalized interactions, all be considered.

Language: Английский

---

Ability of Peripheral H Bonds to Strengthen a Halogen Bond

The Journal of Physical Chemistry A, Journal Year: 2022, Volume and Issue: 126(51), P. 9691 - 9698

Published: Dec. 15, 2022

Quantum calculations study the manner in which involvement of a halogen atom as proton acceptor one or more H bonds (HBs) affects strength bond (XB) it can form with nucleophile aligned X σ-hole. A variety Lewis acids wherein = F, Cl, Br, and I are attached to tetrel C Ge engaged XB NH3. One, two, three HF molecules were positioned perpendicular axis so that they could HB atom. Each such strengthened by an increment 1 kcal/mol does not attenuate each new is added, potentially increasing interaction energy manyfold. Additionally, presence HBs facilitates formation reluctant engage absence these auxiliary interactions. Even F atom, avoids XB, be coaxed participate moderate external HBs.

Language: Английский

---