Mechanochemical Preparations of Anion Coordinated Architectures Based on 3‐Iodoethynylpyridine and 3‐Iodoethynylbenzoic Acid

Abstract

The halogen bond has previously been explored as a versatile tool in crystal engineering and anion coordination chemistry, with mechanochemical synthetic techniques having been shown to provide convenient routes towards cocrystals. In an effort to expand our knowledge on the role of halogen bonding in anion coordination, here we explore a series of cocrystals formed between 3‐iodoethynylpyridine and 3‐iodoethynylbenzoic acid with halide salts. In total, we report the single‐crystal X‐ray structures of six new cocrystals prepared by mechanochemical ball milling, with all structures exhibiting C≡C−I⋅⋅⋅X− (X=Cl, Br) halogen bonds. Whereas cocrystals featuring a pyridine group favoured the formation of discrete entities, cocrystals featuring a benzoic acid group yielded an alternation of halogen and hydrogen bonds. The compounds studied herein were further characterized by 13C and 31P solid‐state nuclear magnetic resonance, with the chemical shifts offering a clear and convenient method of identifying the occurrence of halogen bonding, using the crude product obtained directly from the mechanochemical ball milling. Whereas the 31P chemical shifts were quickly able to identify the occurrence of cocrystallization, 13C solid‐state NMR was diagnostic of both the occurrence of halogen bonding and of hydrogen bonding.

Anticooperativity and Competition in Some Cocrystals Featuring Iodine‐Nitrogen Halogen Bonds

“…Several reports have described the influence of halogen bonding on the NMR chemical shift response, particularly for 13 C and 19 F nuclides. [10,16,28,48,43,44,45,46,47,48,49,50] Shown in Figure 7 are the 13 C MAS NMR spectra of 3-aminopyridine and of cocrystal 1 b. The aromatic resonances of 3-aminopyridine are seen to generally become more shielded and broader upon halogenbond induced cocrystallization.…”

“…Several reports have described the influence of halogen bonding on the NMR chemical shift response, particularly for 13 C and 19 F nuclides [10,16,28,48,43,44,45,46,47,48,49,50] . Shown in Figure 7 are the 13 C MAS NMR spectra of 3‐aminopyridine and of cocrystal 1 b .…”

Stoichiomorphic halogen-bonded cocrystals: a case study of 1,4-diiodotetrafluorobenzene and 3-nitropyridine

“…Furthermore, the low melting point of 3-nitropyridine (35-40°C) means that cocrystallization could potentially provide a route to stabilizing this component in a higher-melting solid phase. In addition to employing single-crystal and powder X-ray diffraction methods for characterization of the stoichiomorphs, we also demonstrate the value of 1 H → 13 C and 19 F → 13 C cross-polarization magic angle spinning (CP/MAS) NMR experiments both to confirm cocrystal formation 16,17,18 in powdered samples and for spectral editing purposes.…”

“…This substantial frequency shift is due to relativistic heavy-atom effects on light-atom shielding (HALA) effects 28,29,30,31 of the heavy 127 I nuclide on 13 C, and has been noted previously in several halogen-bonded systems. 16,18,32,33 A close inspection of the C-I peak for pure 1,4diiodotetrafluorobenzene and that for cocrystal D reveals only a very small change in peak position, from 76.8 ± 1.4 ppm to 77.2 ± 1.5 ppm. The shift to higher 13 C frequencies upon formation of a halogen bond to iodine is consistent with several previous reports.…”

Solid-state multinuclear magnetic resonance and X-ray crystallographic investigation of the phosphorus...iodine halogen bond in a bis(dicyclohexylphenylphosphine)(1,6-diiodoperfluorohexane) cocrystal

“…Mechanochemistry using a ball mill consists of grinding two or more compounds together in a jar in the presence of grinding balls (Braga et al, 2013;Fischer et al, 2016). Solid-state NMR spectroscopy is well suited as an analytical technique for investigating solids featuring the halogen bond (Xu et al, 2020;Vioglio et al, 2016), such as cocrystals obtained from mechanochemical preparations (Morin et al, 2019;Szell, Dragon et al, 2018), providing clear changes in chemical shifts (Cerreia Viger-Gravel et al, 2013Gao et al, 2012;Pe ´rez-Torralba et al, 2014), quadrupolar coupling constants Cerreia Vioglio et al, 2018;Szell, Gre ´bert & Bryce, 2019;Viger-Gravel, Leclerc et al, 2014;Szell, Cavallo et al, 2018), J-coupling constants (Viger-Gravel, Meyer et al, 2014;Xu et al, 2015), dipolar coupling constants (Weingarth et al, 2008) and dynamics (Szell, Zablotny & Bryce, 2019;Lemouchi et al, 2011;Catalano et al, 2015Catalano et al, , 2017.…”