Halogen‐Bonded Organic Framework (XOF) Based on Iodonium‐Bridged N⋅⋅⋅I⁺⋅⋅⋅N Interactions: A Type of Diphase Periodic Organic Network

Abstract

Due to the fascinating structures and wide applications, porous materials with open frameworks have attracted more and more attentions. Herein, a novel two‐dimensional (2D) halogen‐bonded organic framework (XOF–TPPE) was successfully designed and fabricated by iodonium‐bridged N⋅⋅⋅I+⋅⋅⋅N interactions between pyridyl groups and I+ for the first time. The formation of XOF–TPPE and its linear analogue was monitored by 1H NMR, UV–Vis, X‐ray photoelectron spectroscopy (XPS), IR, SEM, TEM, HRTEM and selected‐area electron diffraction (SAED). The structural model of XOF–TPPE was established based on powder X‐ray diffraction (PXRD) data and theoretical simulations. Significantly, synchrotron small‐angle X‐ray scattering (SAXS), DLS and UV–Vis spectroscopy experiments suggested that XOF–TPPE still maintains a stable 2D framework structure in solutions. This research opens up a novel avenue for the development of organic frameworks materials, and may bring new promising applications for the field of porous materials.

The Influence of Secondary Interactions on the [N−I−N]+ Halogen Bond

“… [26] Moreover, understanding the influence of strain, steric and electronic effects along with that of chelation on the three‐center halogen bond of halonium ions will also enable the development of more complex supramolecular assemblies[ 14a , 14b , 14c , 14f ] and halogen‐bonded organic frameworks (XOFs). [15] It may in addition provide helpful knowledge for the development of structurally closely related organometallic reagents [27] and systems held together by other types of three‐center, four‐electron bonds, such as tetrel, pnictogen and chalcogen bonds. [11] The bis(pyridine)iodine(I) complex has lately been proposed to be involved in a spectacular cation‐cation interaction,[ 18a , 28 ] for which the influence of steric and electronic effects, strain, crystal packing forces and hydrophobic stacking are yet by far not well understood.…”

“… [12] Three‐center, four‐electron halogen bond complexes receive increasing attention,[ 9a , 10 , 13 ] not least because they are applicable as mild halonium transfer and oxidation agents in synthesis,[ 7a , 7b , 7c , 7d , 7e , 7f , 7g , 7h , 7j , 7k , 7l , 7m , 7n ] as novel supramolecular synthons in the assembly of complex architectures, [14] and as a key element in halogen bonded frameworks. [15] Fundamental investigations primarily included symmetry determination, where the effect of varying the halogen,[ 13a , 13d ] the solvent, [10] the counter ion, [13e] and the electron density of the Lewis bases[ 13b , 13c , 14d ] have been assessed. The [N−X−N] + bond was shown to prefer a static, symmetric geometry, which can be desymmetrized by using Lewis bases of different electron density.…”

“…An improved understanding of the influence of steric and electronic effects on the three‐center halogen bond is expected to enable the rational modulation of the reactivity of bis(pyridine)halogen(I)‐type halonium transfer synthetic agents, and facilitate their applications for instance in the design of complex supramolecular systems,[ 14c , 14f , 14g , 18 ] and in halogen‐bonded organic frameworks. [15] …”

Halogen‐Bonded Organic Framework (XOF) Based on Iodonium‐Bridged N⋅⋅⋅I+⋅⋅⋅N Interactions: A Type of Diphase Periodic Organic Network

“…(d) Single crystal structure of MOF-BPy with different views. [22] Angewandte Chemie Zuschriften 14958 www.angewandte.de…”

“…Figure 1. (a) XPS spectrum of I 3d for XOF-BPy; (b) Partial 1 H NMR spectra of BPy, MOF-BPy and XOF-BPy in CDCl 3 /[D 4 ]MeOH (4:1, v/v, 600 MHz, 298 K); (c) IR spectra of BPy, MOF-BPy, XOF-BPy;(d) Single crystal structure of MOF-BPy with different views [22]. …”