Highly Fluorinated Trianglimine Macrocycles: A Supramolecular Organic Framework

Abstract

In a two-step synthesis, a novel highly fluorinated dialdehyde is accessible. This very reactive building block for dynamic imine chemistry is exemplarily utilized in a condensation reaction to generate the first extensively fluorinated trianglimine. The analysis of the material properties and especially the crystal structure of the [3+3] macrocycle reveal a supramolecular organic framework with tubular porous channels. The use of fluorinated ligands to generate hydrophobic, electron-deficient channel-like pores is an important addition to the ever-expanding field of supramolecular networks and trianglimine chemistry in general.

Porous Organic Compounds – Small Pores on the Rise

“…A highly fluorinated trianglimine macrocycle T4 was synthesized and exhibits a chiral helical pore in the solid-state with again accessible voids depicted in dark blue, stable also upon desolvation. [27] Structures determined from SXRD with hydrogen atoms and solvent molecules omitted for clarity. The quality of the collected data was not sufficient to determine the nature of the iodo-species entrapped within the channels, however, Raman studies revealed the presence of polyiodide (I 3 À and I 5 À ) rather than iodine.…”

“… [22b] Following these initial results, a variety of articles were published in close succession, mainly focusing on the synthetical aspects, [22‐23] such as diversification by formaldehyde tying, [22a] the inherent chirality or host‐guest interactions in solution, [23] obtained crystal structures mainly being a supplement. Although even in the earliest works either inclusion complexes or pores, when omitting the solvent from the structure, could be observed in the solid‐state, [22c,24] it took another decade until groups started focusing on the solid‐state adsorption properties [24–27] . Other than POCs with their inherent 3‐dimensional cavity, in the 2‐dimensional structure of macrocycles only a planar void (hole) is present.…”

“…In contrast to the previous examples, Schmidt et al . reported the first highly fluorinated trianglimine based SOF by employing aldehyde 23 , altering the steric and electronic effects of the used building block [27] . The fluorinated trianglimine SOF FT‐SOF‐1 was formed by simple crystallization of trianglimine T4 from a DCM/MeCN solution as long, needle‐shaped crystals.…”

“…Although even in the earliest works either inclusion complexes or pores, when omitting the solvent from the structure, could be observed in the solid-state, [22c,24] it took another decade until groups started focusing on the solid-state adsorption properties. [24][25][26][27] Other than POCs with their inherent 3-dimensional cavity, in the 2-dimensional structure of macrocycles only a planar void (hole) is present. If multiple units are stacked in a layered fashion, then tubular 1D pores (channels) are formed.…”

“…In contrast to the previous examples, Schmidt et al reported the first highly fluorinated trianglimine based SOF by employing aldehyde 23, altering the steric and electronic effects of the used building block. [27] The fluorinated trianglimine SOF FT-SOF-1 was formed by simple crystallization of trianglimine T4 from a DCM/MeCN solution as long, needle-shaped crystals. Interlayer CÀ F•••π and CÀ H•••F interactions, [20] as well as the twisted fluorinated biphenyl panels, caused by the higher steric demands of the fluorine substituents enabled the formation of a unique helical 1D pore (Figure 11 bottom).…”