Solvent and Guest-Driven Supramolecular Organic Frameworks Based on a Calix[4]arene-tetrol: Channels vs Molecular Cavities

Neal Hickey,Margherita De Rosa,Carmine Gaeta,Veronica Iuliano,Silvano Geremia,Placido Neri,Carmen Talotta,Annunziata Soriente

doi:10.1021/acs.cgd.1c00828

Neal Hickey, Margherita De Rosa + Show 6 more

Open Access

https://doi.org/10.1021/acs.cgd.1c00828

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Abstract

Cone-shaped calix[4]arene-tetrol 3 has the ability to form open structures due to the presence of four OH groups at the upper rim, which allows the construction of H-bonded supramolecular organic frameworks (SOFs). In the presence of water, SOF-1 is formed, which contains hydrophilic channels (mean diameter of 8.5 Å) contoured by the p-phenolic OH groups. In the presence of acetonitrile, SOF-2 is formed, which contains smaller hydrophobic channels (mean diameter of 6.6 Å) delimited by aromatic walls. The Na+@3 complex, which hosts acetonitrile molecules in the calixarene cavities, and dibromo-calix[4]arene-diol 5 give rise to more compact SOFs not containing channels. The H-bond network formed by all four p-phenolic OH groups in a pinched cone conformation of the calixarene is a determinant for the porosity of SOFs based on calix[4]arene-tetrol.

Highlights

Supramolecular organic frameworks (SOFs)1−8 have attracted significant attention due to their potential applications in gas storage and separation.9,10 supramolecular organic frameworks (SOFs) are structural analogues of the well-known metal−organic frameworks (MOFs)11−14 and covalent organic frameworks (COFs),15,16 and can be defined as porous molecular solids built from organic subunits assembled through weak noncovalent interactions
This molecule has the ability to form open structures due to the presence of four OH groups at the upper rim, which allows the construction of a H-bonded framework
In the presence of water, hydrophilic channels are formed by the phenolic OH groups which point toward the center of the SOF-1 channels

Summary

■ INTRODUCTION

Supramolecular organic frameworks (SOFs)− have attracted significant attention due to their potential applications in gas storage and separation. SOFs are structural analogues of the well-known metal−organic frameworks (MOFs)− and covalent organic frameworks (COFs), and can be defined as porous molecular solids built from organic subunits assembled through weak noncovalent interactions. The raw product was purified through a silica gel chromatography column using solvent mixture 70:30 petroleum ether/chloroform as eluent. The crude product was purified through a silica gel chromatography column using solvent mixture 90:10 chloroform/methanol as eluent. 1.3 mL of a 9:1 chloroform/methanol hot mixture and crystallized by slow evaporation, obtaining single crystals suitable for X-ray diffraction. SOF-2: 4.0 mg of compound 3 was dissolved in 1.3 mL of a 9:1 chloroform/acetonitrile hot mixture and crystallized by slow evaporation obtaining single crystals suitable for X-ray diffraction. SOF-3: A mixture 1:1 of compound 3 (6.8 mg) and NaI (1.6 mg) was dissolved in 0.6 mL of a 3:1 chloroform/acetonitrile hot mixture and crystallized by slow evaporation obtaining single crystals suitable for X-ray diffraction. Additional X-ray diffraction experiments were performed on SOF-1 after treatment in air at room temperature and at 60 °C using a conventional source (see the SI)

■ RESULTS AND DISCUSSION

■ CONCLUSIONS

■ REFERENCES