The formation of supramolecular parallelograms utilizing iodoalkyne–pyridine halogen bonding is described. The crystal structures of four iodoalkynyl-substituted (phenylethynyl)pyridines demonstrate ...the feasibility of discrete self-complementary dimer formation. These compounds 3-(2-iodoethynyl-phenylethynyl) pyridine (1), 2-(3-iodoethynyl-phenylethynyl) pyridine (2), 3-(4,5-difluoro-2-iodoethynyl-phenylethynyl) pyridine (3), and 2-(5-iodoethynyl-2,4-dimethylphenylethynyl) pyridine (4) all form parallelogram-shaped dimers with two self-complementary short N–I halogen bonds. The potential formation of iodoalkynyl halogen-bonded supramolecular macrocycles is demonstrated by the formation of a discrete halogen-bonded parallelogram-shaped complex in the 1:1 cocrystal formed from the bis iodoalkyne, 1-iodoethynyl-2-(3-iodoethynyl-phenylethynyl)-4,5-dimethoxybenzene (6), and the dipyridyl, 5-phenyl-2-(pyridin-3-ylethynyl)pyridine (7). Furthermore, discrete supramolecular parallelograms form within the 2:2 cocrystal formed between 1,2-bis(iodoethynyl)-4,5-difluorobenzene and the dipyridyl 4-(3-pyridylethynyl) pyridine (8).
Cooperative strong charge-assisted hydrogen bonding and weaker nonconventional hydrogen bonding are probed through cocrystals formed between 2,3,5,6-tetrafluorobenzoic acid and three ...2-aminopyrazines. In each of these cocrystals, cooperative nonconventional hydrogen bonding and charge-assisted hydrogen bonding results in the formation of hydrogen-bonded supramolecular networks. A charge-assisted cyclic hydrogen bonded motif, R2 2(8), is formed between the 2-aminopyrazinium cation and the carboxylate anion along with a nonconventional C–H···N hydrogen bond between the phenyl hydrogen and second ring N in the pyrazine. Secondary hydrogen bonding interactions result in the formation of a double-stranded linear polymer, a planar 2D polymer, or an interconnected 3D network depending on secondary substitution of the 2-aminopyrazine. The related formation of both 1:1 and 2:1 cocrystals between 4-pyrrolidinopyridine and 2,3,5,6-tetrafluorobenzoic acid is also reported.
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.
The X‐ray structures of three 1:1 cocrystals formed between reactive diethynylpyridine and N‐halosuccinimide partners are reported. Each cocrystal features a short halogen bond and two short complementary nonconventional C—H…O hydrogen bonds.
This study expands and combines concepts from two of our earlier studies. One study reported the complementary halogen bonding and π-π charge transfer complexation observed between isomeric electron ...rich 4-
,
-dimethylaminophenylethynylpyridines and the electron poor halogen bond donor, 1-(3,5-dinitrophenylethynyl)-2,3,5,6-tetrafluoro-4-iodobenzene while the second study elaborated the ditopic halogen bonding of activated pyrimidines. Leveraging our understanding on the combination of these non-covalent interactions, we describe cocrystallization featuring ditopic halogen bonding and π-stacking. Specifically, red cocrystals are formed between the ditopic electron poor halogen bond donor 1-(3,5-dinitrophenylethynyl)-2,4,6-triflouro-3,5-diiodobenzene and each of electron rich pyrimidines 2- and 5-(4-
,
-dimethyl-aminophenylethynyl)pyrimidine. The X-ray single crystal structures of these cocrystals are described in terms of halogen bonding and electron donor-acceptor π-complexation. Computations confirm that the donor-acceptor π-stacking interactions are consistently stronger than the halogen bonding interactions and that there is cooperativity between π-stacking and halogen bonding in the crystals.
The role of phenyl C–H···N interactions in crystal engineering is explored with a variety of fluorinated phenyl-containing compounds. In particular, we show that this interaction can guide the ...formation of one-dimensional phenyl C–H···N hydrogen-bonded ribbons with, for example, 4-(2,3,5,6-tetrafluorophenylethynyl)pyridine. The interaction is shown to also control the formation of self-complementary homodimers with 3-(2,3,4,5-tetrafluorophenylethynyl)pyridine. We also demonstrate that the phenyl C–H···N hydrogen bond interaction is capable of enticing co-crystallization of molecules such as 2,3,5,6,2′,3′,5′,6′-octafluorobiphenyl and 4,4′-dipyridyl. Finally, we describe the use of an intramolecular scaffold to evaluate the effect of electron-withdrawing substituents on the strength of a phenyl C–H···N hydrogen bond.
Triple pnictogen bonding refers to the ability of a pnictogen atom to engage in three simultaneous pnictogen bonds (PnBs) to a complementary partner through a single pnictogen atom. This ...supramolecular strategy was recently introduced as a unique facet of pnictogen bonding as compared to other named supramolecular interactions. Here, the ability of bismuth to participate in this phenomenon is demonstrated using Bi((NC9H7)3CH3). The study reveals that Bi engages in stronger PnBs than the analogous Sb system. The results have been contrasted with Bi systems that form strong coordination bonds, and analysis of the electron density along the bond path reveals key differences. The solution behavior of these newly synthesized supramolecules were studied by PFGSE NMR spectroscopy and they are found to remain intact in solution. Molecular design strategies that allow for triple pnictogen bonding should find use in the fields of molecular recognition and crystal engineering.
Supramolecular assembly utilizing simultaneous formation of three pnictogen bonds around a single antimony vertex was explored via X-ray crystallography, solution NMR, and computational chemistry. An ...arylethynyl (AE) ligand was designed to complement the three electrophilic regions around the Sb compound. Though solution studies reveal large binding constants for individual pyridyl units with the Sb donor, the rigidity and prearrangement of the AE acceptor proved necessary to achieve simultaneous binding of three acceptors to the Sb-centered pnictogen-bond donor. Calculations and X-ray structures suggest that negative cooperativity upon sequential binding of three acceptors to a Sb center limits the utility of triple-pnictogen bonding pyridyl acceptors. These limitations can be negated, however, when positive cooperativity is designed into a complementary acceptor ligand.
The present study evaluates the potential combination of charge‐transfer electron‐donor–acceptor π–π complexation and C—H hydrogen bonding to form colored cocrystals. The crystal structures of the ...red 1:1 cocrystals formed from the isomeric pyridines 4‐ and 3‐{2‐4‐(dimethylamino)phenylethynyl}pyridine with 1‐2‐(3,5‐dinitrophenyl)ethynyl‐2,3,5,6‐tetrafluorobenzene, both C14H4F4N2O4·C15H14N2, are reported. Intermolecular interaction energy calculations confirm that π‐stacking interactions dominate the intermolecular interactions within each crystal structure. The close contacts revealed by Hirshfeld surface calculations are predominantly C—H interactions with N, O, and F atoms.
Colored 1:1 cocrystals are formed between 1‐2‐(3,5‐dinitrophenyl)ethynyl‐2,3,5,6‐tetrafluorobenzene and the isomeric pyridines 4‐ and 3‐{2‐4‐(dimethylamino)phenylethynyl}pyridine. The cocrystals feature attractive π–π stacking and C—H hydrogen bonding.
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 (C
4
H
4
INO
2
·C
9
H
5
N) 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 (C
4
H
4
INO
2
·C
9
H
5
N) 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 (C
4
H
4
BrNO
2
·C
9
H
5
N) 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.
1,3‐Diiodo‐5‐nitrobenzene, C6H3I2NO2, and 1,3‐dibromo‐5‐nitrobenzene, C6H3Br2NO2, crystallize in the centrosymmetric space group P21/m, and are isostructural with 1,3‐dichloro‐5‐nitrobenzene, ...C6H3Cl2NO2, that has been redetermined at 100 K for consistency. While the three‐dimensional packing in all three structures is similar, the size of the halogen atom affects the nonbonded close contacts observed between molecules. Thus, the structure of 1,3‐diiodo‐5‐nitrobenzene features a close Type 1 I…I contact, the structure of 1,3‐dibromo‐5‐nitrobenzene features a self‐complementary nitro‐O…Br close contact, while the structure of 1,3‐dichloro‐5‐nitrobenzene also has a self‐complementary nitro‐O…Cl interaction, as well as a bifurcated C—H…O(nitro) close contact. Notably, the major energetically attractive intermolecular interaction between adjacent molecules in each of the three structures corresponds to a π‐stacked interaction. The self‐complementary halogen…O(nitro) and C—H…O(nitro) interactions correspond to significant cohesive attraction between molecules in each structure, while the Type 1 halogen–halogen contact is weakly cohesive.
The relationship between close intermolecular contacts and intermolecular energies of interaction within the crystals of the 1,3‐dihalo‐5‐nitrobenzenes with Cl, Br, and I is probed. The results reveal the relative role of π‐stacking, self‐complementary halogen…O(nitro) bonds, bifurcated C—H…O(nitro) interactions and Type I halogen–halogen interactions in terms of cohesive intermolecular energies of interaction.
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