The X-ray structure of a series of iodo- and bromo-phenylethynylpyridines designed to form self-complementary dimers in the solid state are reported. The perfluoroiodo- and ...perfluorobromophenylethynyl derivatives, 3-(2-bromo-3,4,5,6-tetrafluorophenyl)ethynylpyridine, 3-(2,3,4,5-tetrafluoro-6-iodophenyl)ethynylpyridine, 2-(3-bromo-2,4,5,6-tetrafluorophenyl)ethynylpyridine, and 2-(2,4,6-trifluoro-3,5-diiodophenyl)ethynylpyridine, formed self-complementary halogen-bonded dimeric units in the solid state. In contrast, 3-(2-bromo-4,5-difluorophenyl)ethynylpyridine formed a C–H···N hydrogen-bonded dimer.
Abstract
A molecular rotor is created when a 2,1,3‐benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag
+
or PdCl
2
) ...guest. Comparisons to a similarly sized naphthyl rotator via
1
H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through‐space interaction of the central arene with a bound PdCl
2
guest. Further study via X‐ray crystallography illustrates that rotation of the 2,1,3‐benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S‐2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid‐state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration.
Co‐crystallization of a pyridyl‐containing arylethynyl (AE) moiety with 1,4‐diiodotetrafluorobenzene leads to unique, figure‐eight shaped helical motifs within the crystal lattice. A slight twist in ...the AE backbone allows each AE unit to simultaneously interact with haloarene units that are stacked on top of one another. Left‐handed (M) and right‐handed (P) helices are interspersed in a regular pattern throughout the crystal. The major driving forces for assembly are 1) halogen bonding between the pyridyl nitrogen atoms and the iodine substituents of the haloarene, with N⋅⋅⋅I distances between 2.81 and 2.84 Å, and 2) π‐π stacking of the haloarenes, with distances of approximately 3.57 Å between centroids. Halogen bonding and π‐π stacking not only work in concert, but also seem to mutually enhance one another. Calculations suggest that the presence of π‐π stacking modestly intensifies the halogen bonding interaction by <0.2 kcal/mol; likewise, halogen bonding to the haloarene enhances the π‐π stacking interaction by 0.59 kcal/mol.
Halogen bonding serves as a primary driving force for the formation of helices of pyridyl‐containing arylethynyl units with halorenes. The role of π‐π stacking in not only reinforcing the supramolecular construct, but also seemingly enhancing the strength of the halogen bond, is explored.
We report the design, synthesis, and crystal structure of a conjugated aryleneethynyl molecule, ...2‐(2‐{4,5‐dimethoxy‐2‐2‐(2,3,4‐trifluorophenyl)ethynylphenyl}ethynyl)‐6‐2‐(pyridin‐2‐yl)ethynylpyridine, C30H17F3N2O2, that adopts a planar rhombus conformation in the solid state. The molecule crystallizes in the space group P, with Z = 2, and features two intramolecular sp2‐C—H…N hydrogen bonds that co‐operatively hold the arylethynyl molecule in a rhombus conformation. The H atoms are activated towards hydrogen bonding since they are situated on a trifluorophenyl ring and the H…N distances are 2.470 (16) and 2.646 (16) Å, with C—H…N angles of 161.7 (2) and 164.7 (2)°, respectively. Molecular electrostatic potential calculations support the formation of C—H…N hydrogen bonds to the trifluorophenyl moiety. Hirshfeld surface analysis identifies a self‐complementary C—H…O dimeric interaction between adjacent 1,2‐dimethoxybenzene segments that is shown to be common in structures containing that moiety.
Co‐operative nonconventional sp2‐C—H…N hydrogen bonds control the conformation of a dipyridyl molecule to a rhombus shape.
Macrocycle formation that relies upon trans metal coordination of appropriately placed pyridine ligands within an arylene ethynylene construct provides rapid and reliable access to molecular rotators ...encapsulated within macrocyclic stators. Showing no significant close contacts to the central rotators, X-ray crystallography of Ag
-coordinated macrocycles provides plausibility for unobstructed rotation or wobbling of rotators within the central cavity. Solid-state
C NMR of Pd
-coordinated macrocycles supports the notion of unobstructed movement of simple arenes in the crystal lattice. Solution
H NMR studies indicate complete and immediate macrocycle formation upon the introduction of Pd
to the pyridyl-based ligand at room temperature. Moreover, the formed macrocycle is stable in solution; a lack of significant changes in the
H NMR spectrum upon cooling to -50 °C is consistent with the absence of dynamic behavior. The synthetic route to these macrocycles is expedient and modular, providing access to rather complex constructs in four simple steps involving Sonogashira coupling and deprotection reactions.
We've got you surrounded! Conjugated units that are encapsulated within the cavities of macrocycles can have unique properties often including the ability to rotate or wobble within an otherwise ...stationary crystal lattice. We introduce a strategy for forming macrocycles of this type in only a few synthetic steps using pyridine coordination to transition metals as the final, ring‐closing step. More information can be found in the Research Article by N. P. Bowling and co‐workers. (DOI: 10.1002/chem.202301745).
We report the design, synthesis, and crystal structure of a conjugated aryleneethynyl molecule, ...2-(2-{4,5-dimethoxy-2-2-(2,3,4-trifluorophenyl)ethynylphenyl}ethynyl)-6-2-(pyridin-2-yl)ethynylpyridine, C
30
H
17
F
3
N
2
O
2
, that adopts a planar rhombus conformation in the solid state. The molecule crystallizes in the space group
P
-1, with
Z
= 2, and features two intramolecular
sp
2
-C—H...N hydrogen bonds that co-operatively hold the arylethynyl molecule in a rhombus conformation. The H atoms are activated towards hydrogen bonding since they are situated on a trifluorophenyl ring and the H...N distances are 2.470 (16) and 2.646 (16) Å, with C—H...N angles of 161.7 (2) and 164.7 (2)°, respectively. Molecular electrostatic potential calculations support the formation of C—H...N hydrogen bonds to the trifluorophenyl moiety. Hirshfeld surface analysis identifies a self-complementary C—H...O dimeric interaction between adjacent 1,2-dimethoxybenzene segments that is shown to be common in structures containing that moiety.
The potential of pyrimidines to serve as ditopic halogen‐bond acceptors is explored. The halogen‐bonded cocrystals formed from solutions of either 5,5′‐bipyrimidine (C8H6N4) or ...1,2‐bis(pyrimidin‐5‐yl)ethyne (C10H6N4) and 2 molar equivalents of 1,3‐diiodotetrafluorobenzene (C6F4I2) have a 1:1 composition. Each pyrimidine moiety acts as a single halogen‐bond acceptor and the bipyrimidines act as ditopic halogen‐bond acceptors. In contrast, the activated pyrimidines 2‐ and 5‐{4‐(dimethylamino)phenylethynyl}pyrimidine (C14H13N3) are ditopic halogen‐bond acceptors, and 1:1 halogen‐bonded cocrystals are formed from 1:1 mixtures of each of the activated pyrimidines and either 1,2‐ or 1,3‐diiodotetrafluorobenzene. A 1:1 cocrystal was also formed between 2‐{4‐(dimethylamino)phenylethynyl}pyrimidine and 1,4‐diiodotetrafluorobenzene, while a 2:1 cocrystal was formed between 5‐{4‐(dimethylamino)phenylethynyl}pyrimidine and 1,4‐diiodotetrafluorobenzene.
The role of activated pyrimidines and bipyrimidines as ditopic halogen‐bond acceptors is demonstrated.
A conjugated, pyridine‐containing, phenylethynyl ligand that forms complexes with AgI and PdII has been developed. NMR titration studies with PdII reveal a stoichiometric binding of the ligand to the ...metal atom, while similar studies with AgI reveal a binding that is dynamic on the NMR timescale. Analysis of the NMR spectroscopic data by Job's plot analysis and non‐linear curve fitting of a titration curve reveals a 1:1 binding ratio of ligand/silver cation and an association constant of Ka = 53 M–1. X‐ray crystal structures of the ligand–metal complexes suggest ample room for the nearly barrierless rotation of the unsubstituted central benzene ring of the para‐phenylethynyl chain. Subtle electronic differences in substituted systems provide some evidence of impaired rotation.
Conjugated ligands: A trans‐spanning ligand that binds AgI and PdII has been developed and studied by X‐ray crystallography and 1H NMR spectroscopy. UV/Vis spectroscopy was used to investigate what effect metal binding might have on the conjugation in the para‐phenyleneethynylene backbone.
