Co-operative halogen bonds and nonconventional sp-C—H...O hydrogen bonds in 1:1 cocrystals formed between diethynylpyridines and N-halosuccinimides

Abstract

The rapid evaporation of 1:1 solutions of diethynylpyridines and N-halosuccinimides, that react together to form haloalkynes, led to the isolation of unreacted 1:1 cocrystals of the two components. The 1:1 cocrystal formed between 2,6-diethynylpyridine and N-iodosuccinimide (C4H4INO2·C9H5N) contains an N-iodosuccinimide–pyridine I...N halogen bond and two terminal alkyne–succinimide carbonyl C—H...O hydrogen bonds. The three-dimensional extended structure features interwoven double-stranded supramolecular polymers that are interconnected through halogen bonds. The cocrystal formed between 3,5-diethynylpyridine and N-iodosuccinimide (C4H4INO2·C9H5N) also features an I...N halogen bond and two C—H...O hydrogen bonds. However, the components form essentially planar double-stranded one-dimensional zigzag supramolecular polymers. The cocrystal formed between 3,5-diethynylpyridine and N-bromosuccinimide (C4H4BrNO2·C9H5N) is isomorphous to the cocrystal formed between 3,5-diethynylpyridine and N-iodosuccinimide, with a Br...N halogen bond instead of an I...N halogen bond.

Hydrogen vs Halogen-Bonded R22(8) Rings in Organic Crystal Structures

“…Four structures (AKIXUP, AKIYAW, EZIBOG, EZICEX) contain N–X···OC contacts that appear to be secondary to N–X···N interactions that are also present as they are longer (2.69–2.91 Å compared to 2.30–2.44 Å for N–X···N). The presence of N–X···N bonds has also been shown to promote the formation of hydrogen bonds involving the neighboring CO moiety in halosuccinimides through cooperativity …”

“…44−46 Some N−X•••N and N−X•••X interactions in these structures are so strong that X•••N is indicated as a formal bond (12/123). 50 In the case of single component crystals, 82% (18/22) form an N−X•••O�C halogen bond; the remaining four structures form a type 1 Cl•••Cl contact (QASXEO), 51 Cl•••π (UPOHIS), 52 or X•••H contacts (PAKBOV, 53 VITHIP 54 ). Only 1 of the 140 crystal structures exhibits an R 2 2 (8) halogen-bonded ring: YOPJUJ (Figure 1).…”

Halogen-Bonded Supramolecular Parallelograms: From Self-Complementary Iodoalkyne Halogen-Bonded Dimers to 1:1 and 2:2 Iodoalkyne Halogen-Bonded Cocrystals

“…In this study, we focus on iodoalkynes that are excellent halogen bond donors, , with the caveat that they are, however, occasionally somewhat more fugitive during preparation . Accordingly, we report here the formation of parallelogram-shaped dimers featuring iodoalkynes as the halogen bond donor and further extend this to the intentional formation of 1:1 and 2:2 cocrystals that feature parallelogram-shaped supramolecular macrocycles using deliberate combinations of bis -iodoalkynes and bipyridines.…”

Comparison of N···I and N···O Halogen Bonds in Organoiodine Cocrystals of Heterocyclic Aromatic Diazine Mono-N-oxides

“…Of the halogens, the highly polarizable diiodine molecule typically forms stronger interactions and is less prone to oxidation of the electron pair donor molecule, which makes diiodine, and polyiodides in general, useful choices for halogen-bonding-directed crystal engineering. − However, diiodine is still a potent oxidizer and, thus, can be limited in its potential utility as a supramolecular building block. These limitations can be addressed by utilizing other forms of iodine that are less oxidizing, such as organoiodines. − By inserting an organic ‘spacer’ between the two iodine atoms, the functionality of a polarized iodine atom can be retained while it exhibits less oxidation strength. The organic spacers also offer a means for influencing the Lewis acidity of the electron pair acceptors in these compounds by adjusting the electron density around the iodine atom .…”