Examination of the solid state structures of 2,1,3benzoselenadiazole complexes with hydrogen or halogen bond donors has demonstrated that the 2,1,3-benzoselenadiazole molecules preferably form centrosymmetric dimers with use of [Se−N] 2 supramolecular synthon, whereas the two remaining nitrogen atoms not involved in the [Se−N] 2 supramolecular interactions can act as acceptors of hydrogen or halogen bonds. Cocrystallization of selenadiazoles with monofunctional hydrogen or halogen bond donors like pentafluorophenol, pentafluorobenzoic acid, or pentafluoroiodobenzene results in formation of binary discrete complexes. One-or two-dimensional aggregates based on selenadiazole [Se−N] 2 dimers as building blocks were prepared using bifunctional hydrogen or halogen bond donors like resorcinol, tetrafluororesorcinol, tetrafluorohydroquinone, and 1,4-diiodotetrafluorobenzene. During the complexation of selenadiazoles with hydroquinone, anilic acid, or chloranilic acid a competition between Se•••N and Se•••O interactions resulted in breaking of the [Se−N] 2 synthon.

ABSTRACT:The 'off' state for aminocatalysis by a switchable [2]rotaxane is shown to correspond to an 'on' state for anion-binding catalysis. Conversely, the aminocatalysis 'on' state of the dual-function rotaxane is inactive in anion-binding catalysis. Switching between the different states is achieved through the stimuli-induced change of position of the macrocycle on the rotaxane thread. The anion-binding catalysis results from a pair of triazolium groups that act together to CHhydrogen bond to halide anions when the macrocycle is located on an alternative (ammonium) binding site, stabilizing the in situ generation of benzhydryl cation and oxonium ion intermediates from activated alkyl halides. The aminocatalysis and anion-binding catalysis sites of the dual-function rotaxane catalyst can be sequentially concealed or revealed, enabling catalysis of both steps of a tandem reaction process.

Directional self-assembly of uncharged molecules in water is am ajor challenge in supramolecular chemistry. Herein,i ti sdemonstrated that peptide-based cavitands wrap around ah ydrophobic core (fullerene C 60 )b yacombination of the hydrophobic effect and hydrogen-bonding interactions to form highly ordered three-componentc omplexes in water that resemblet he molten-globule stage of proteinf olding. The complexesw ere characterized by DOSY NMR spectroscopy,s mall-angleX -ray scattering, andc ircular dichroism, and their structuresw ere confirmed by X-ray crystallography.E nhancemento ft he CD signalsb yn early one order of magnitude and increased hydrolytic stability of hydrazone bonds of the complexes relative to the nonassembled species were observed.I nc ontrast, DMSO and DMSO/ waterm ixtures were found to be highly disintegrative for these complexes. Interestingly,s ome cavitands cano nly be synthesized in the presence of the hydrophobic template followed by disassemblyoft he complexes.[a] Dr.Supporting information and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Rational manipulation of secondary bonding interactions is a crucial factor in the construction of new chalcogenadiazole-based materials. This article reports detailed experimental studies on phenanthro[9,10-c][1,2,5]chalcogenadiazolium and 2,1,3-benzochalcogenadiazolium salts and their precursors. The compounds were synthesized, characterized employing NMR and UV-Vis spectroscopy. TD-DFT calculations were also performed. The influence of the size of the aromatic system on the molecular motifs formed by the compounds in the solid state has been studied by means of single-crystal X-ray diffraction. In case of the salts, the nature of an anion was also taken into consideration. The results show that cyclic [E···N]2 supramolecular synthon connects neighboring molecules of phenanthro[9,10-c][1,2,5]chalcogenadiazoles, with a relatively large aromatic system, in dimers regardless of the chalcogen atom in the molecule. Both N-methyl-2,1,3-benzothiadiazolium and N-methylphenanthro[9,10-c][1,2,5]chalcogenadiazolium cations have a strong affinity for triflate and iodide anions, therefore the formation of S···N or Se···N secondary bonding interactions is observed only in two out of the eight quaternary salts. Less coordinating anions must be used to enable the building blocks studied to form cyclic [E···N]2 synthons. Moreover, for two of the triflate salts, which are isostructural, a new supramolecular motif has been observed.

Two crystalline supramolecular polypseudorotaxanes were obtained by combining permethylated pillar[5]arene as a macrocyclic wheel with 1,4-bisIJ1-imidazolyl)butane and 1,4-bisIJiodoethynyl)benzene or 1,4-diiodo-1,3-butadiyne linked by C-I⋯N halogen bonds and creating a polyrotaxane axis. The resulting highly ordered supramolecular arrays were characterized by X-ray crystallography.