Specific Noncovalent Association of Truncated exo-Functionalized Triangular Homochiral Isotrianglimines through Head-to-Head, Tail-to-Tail, and Honeycomb Supramolecular Motifs.

Agnieszka Janiak,Joanna Szymkowiak,Błażej Gierczyk,Jadwiga Gajewy,Marcin Kwit

doi:10.1021/acs.joc.1c02238

Agnieszka Janiak, Joanna Szymkowiak + Show 3 more

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https://doi.org/10.1021/acs.joc.1c02238

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Abstract

Chiral isotrianglimines were synthesized by the [3 + 3] cyclocondensation of (R,R)-1,2-diaminocyclohexane with C5-substituted isophthalaldehyde derivatives. The substituent’s steric and electronic demands and the guest molecules’ nature have affected the conformation of individual macrocycles and their propensity to form supramolecular architectures. In the crystal, the formation of a honeycomb-like packing arrangement of the simplest isotrianglimine was promoted by the presence of toluene or para-xylene molecules. A less symmetrical solvent molecule might force this arrangement to change. Polar substituents present in the macrocycle skeleton have enforced the self-association of isotrianglimines in the form of tail-to-tail dimers. These dimers could be further arranged in higher-order structures of the head-to-head type, which were held together by the solvent molecules. Non-associating isotrianglimine formed a container that accommodated acetonitrile molecules in its cavity. The calculated dimerization energies have indicated a strong preference for the formation of tail-to-tail dimers over those of the capsule type.

Highlights

Since the first works by Ruzǐ cǩ a,1,2 macrocycles and, later on, covalent organic cage compounds have become essential compounds in chemistry, material chemistry, crystal engineering, and biochemistry.3−6 The continuous development of supramolecular chemistry has resulted in macrocyclic compounds being employed as molecular building blocks in molecular tectonics.7−10 This approach allows for the construction of capsules with large internal cavities and is capable of capturing neutral and charged species in addition polymeric structures, where the monomers are bound by noncovalent interactions.11−15
In contrast to the low-yielding kinetics-driven synthesis of imide-based highly symmetrical molecular triangles,16 the cycloimination reactions between structurally predisposed substrates would lead to products of the same shape and symmetry with, as one can even say, much higher quantitative yields.17−21 It was as early as 2000 when Gawronski et al demonstrated the possibility for the quantitative synthesis of a chiral [3 + 3] triangular macrocycle dubbed trianglimine through thermodynamically driven cycloimination of trans(R,R)-diaminocyclohexane (DACH, 1) and terephthalaldehyde
The 1,3-benzenedicarbaldehyde derivatives are commonly considered “difficult” substrates for cycloiminations.17−21,32−34 Whereas terephthalaldehyde itself and its symmetrical derivatives in combination with 1 have provided triangular [3 + 3] products of the highest available D3 symmetry,17 the isophthalaldehydes might lead to the formation of condensation products characterized by the lower C3 symmetry

Summary

INTRODUCTION

Since the first works by Ruzǐ cǩ a,1,2 macrocycles and, later on, covalent organic cage compounds have become essential compounds in chemistry, material chemistry, crystal engineering, and biochemistry.− The continuous development of supramolecular chemistry has resulted in macrocyclic compounds being employed as molecular building blocks in molecular tectonics.− This approach allows for the construction of capsules with large internal cavities and is capable of capturing neutral and charged species in addition polymeric structures, where the monomers are bound by noncovalent interactions.−. In contrast to the low-yielding kinetics-driven synthesis of imide-based highly symmetrical molecular triangles, the cycloimination reactions between structurally predisposed substrates would lead to products of the same shape and symmetry with, as one can even say, much higher quantitative yields.− It was as early as 2000 when Gawronski et al demonstrated the possibility for the quantitative synthesis of a chiral [3 + 3] triangular macrocycle dubbed trianglimine through thermodynamically driven cycloimination of trans(R,R)-diaminocyclohexane (DACH, 1) and terephthalaldehyde .22. The reduced congener of basic trianglimine, namely trianglamine, has shown a propensity to capture of CO2 apart from solvent molecules.49,50 Those mentioned above and other properties of triangular chiral macrocycles are due to the formation of the “proper crystalline phase”.47. As the further spectacular applications of macrocycle-based materials started from rather basic research, in this study we have paid attention to the possibility of creating various supramolecular motifs using the model isotrianglimines 3a−3e. To keep the discussion as concise as possible, the results less relevant to the main topic are skipped but are discussed briefly in the Supporting Information

RESULTS AND DISCUSSION

CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES