Weak hydrogen and halogen bonding in 4-[(2,2-difluoroethoxy)methyl]pyridinium iodide and 4-[(3-chloro-2,2,3,3-tetrafluoropropoxy)methyl]pyridinium iodide

Abstract

To enable a comparison between a C-H...X hydrogen bond and a halogen bond, the structures of two fluorous-substituted pyridinium iodide salts have been determined. 4-[(2,2-Difluoroethoxy)methyl]pyridinium iodide, CHFNO·I, (1), has a -CHOCHCFH substituent at the para position of the pyridinium ring and 4-[(3-chloro-2,2,3,3-tetrafluoropropoxy)methyl]pyridinium iodide, CHClFNO·I, (2), has a -CHOCHCFCFCl substituent at the para position of the pyridinium ring. In salt (1), the iodide anion is involved in one N-H...I and three C-H...I hydrogen bonds, which, together with C-H...F hydrogen bonds, link the cations and anions into a three-dimensional network. For salt (2), the iodide anion is involved in one N-H...I hydrogen bond, two C-H...I hydrogen bonds and one C-Cl...I halogen bond; additional C-H...F and C-F...F interactions link the cations and anions into a three-dimensional arrangement.

Indolyl Phosphine Nickel(II) Fluorido Complexes: Synthesis and Intermediates in Suzuki–Miyaura Cross‐Coupling Reactions

“…The separation between the two fluorine atoms of 2.8581(3) Å is smaller than the sum of their van der Waals radii of 2.94 Å, which might be due to packing effects [68,77] . Although, dispersive F⋅⋅⋅F contacts are also discussed in the literature [78–84] …”

“…[68,77] Although, dispersive F•••F contacts are also discussed in the literature. [78][79][80][81][82][83][84] Various mechanistic steps for a preferred CÀ F bond activation in ortho-position at pentafluoropyridine were discussed, involving a pre-coordination of the aromatic system to a nickel(0) bis(phosphine) species. [54,62,85,86] In 2010 DFT calculations by McGrady and coworkers proposed a phosphine-assisted pathway.…”

Asymmetric Synthesis of Axially Chiral Phosphamides via Atroposelective N-Allylic Alkylation

“…It has to claim that, though the iodine atom have a larger size than methyl (Charton parameters: Me = 0.52; I = 0.78), they exhibit opposite electrostatic features. The orientation of the electronic abundant iodine atom in the favored TS-I-major shows more favorable noncovalent interactions with hydrogens (Figure a) . Meanwhile, in the geometry of the less favored TS-I-minor , the distance of the hydrogen atom of the methyl group with neighboring hydrogen atoms are 2.07 and 2.13 Å (Figure b, red circle mark), which reveals a significant steric repulsion between the methyl group with neighboring hydrogen atoms.…”

Pure Nano Genesis: Pioneering Universal Aqueous Nanostrategies from Pure Molecules to Revolutionise Diverse Applications

“…A fundamental reason for this impediment lies in the inherently weak intermolecular interactions, such as Van der Waals forces (London dispersion force and dipole-dipole forces), hydrogen bonding and hydrophobic interactions (Tendency of hydrophobic moieties to aggregate in aqueous solution), that exist among the assembly chains constituting the nanoparticle skeleton. [6][7][8] Accordingly, nanoparticles formulated via conventional amphiphilic components are particularly vulnerable to instability, thereby engendering phenomena such as coalescence or flocculation, prior to their successful arrival at targeted sites. 8,9 Furthermore, the complex in vivo milieu further exacerbates the stability concerns that excipient-based nanoparticles encounter, primarily via interactions with biological constituents, as well as dilution in the blood.…”