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Abstract
Organic molecules with heavy main-group elements frequently form supramolecular links to electron-rich centres. One particular case of such interactions is halogen bonding. Most studies of this phenomenon have been concerned with either dimers or infinitely extended structures (polymers and lattices) but well-defined cyclic structures remain elusive. Here we present oligomeric aggregates of heterocycles that are linked by chalcogen-centered interactions and behave as genuine macrocyclic species. The molecules of 3-methyl-5-phenyl-1,2-tellurazole 2-oxide assemble a variety of supramolecular aggregates that includes cyclic tetramers and hexamers, as well as a helical polymer. In all these aggregates, the building blocks are connected by Te…O–N bridges. Nuclear magnetic resonance spectroscopic experiments demonstrate that the two types of annular aggregates are persistent in solution. These self-assembled structures form coordination complexes with transition-metal ions, act as fullerene receptors and host small molecules in a crystal.
Highlights
Organic molecules with heavy main-group elements frequently form supramolecular links to electron-rich centres
The short TeyO distances in the crystals structures and the results of mass spectrometry, nuclear magnetic resonance (NMR) spectroscopy and DFT calculations show that the interaction between the tellurium and oxygen atoms is very strong
The observation of aggregates in the electrospray mass spectrum 1b is remarkable; supramolecular dimers assembled by TeyN interactions have been observed in mass spectra acquired from the laser-ablation plume of benzotelluradiazoles[58] but the detection of oligomers with aggregation numbers 3–7 is unprecedented for organo-tellurium molecules
Summary
Organic molecules with heavy main-group elements frequently form supramolecular links to electron-rich centres. The potential of chalcogen-centered interactions in supramolecular chemistry is illustrated by two well-studied molecular families: the dichalcogena alkynes, which consistently crystalize in tubular structures assembled by chalcogen–chalcogen interactions[38,39,40], and the 1,2,5-chalcogenadiazoles, in which two pairs of antiparallel chalcogen–nitrogen interactions per molecule tend to build infinite ribbons The latter structures are of interest because of their charge transport properties[41] and, through moderate steric repulsion, can be distorted to induce non-linear optical properties or chromotropism[42,43,44]. In the halogen-bonding case, IyN interactions have been employed in the construction of molecular capsules[48] from a pair of complementary molecules; the assembly of such structures in solution was recently demonstrated[49,50]
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