Synthesis and structures of N-(4-picolyl)azacalix[4]arene and its bridged derivatives

Autor: Yuri Hayano, Kana Orioka, Asako Kobayashi, Yukako Mogami, Tetsuo Iwanaga, Katsuya Sako, Kanae Okayama, Hiroyuki Takemura, Noriko Nagashima
Rok vydání: 2019
Předmět:
Zdroj: Journal of Inclusion Phenomena and Macrocyclic Chemistry. 95:235-246
ISSN: 1573-1111
1388-3127
Popis: Azacalixarenes have side arms (N-substituents) on the nitrogen atoms in their macrocyclic ring systems; thus, a variety of molecular designs are possible by modifying these side arms. This is a special feature of azacalixarene system which is not available in calix[n]arenes. In this paper, we used azacalix[3.1.3.1] and [3.1.1.1]arenes because these compounds have concave cavities. The cavity size of the azacalix[3.1.1.1] structure is small like the calix[4]arenes, but, supramolecular systems can be designed in which two or three azacalix units are connected by covalent or coordination bonds. Previously reported compounds, N-(4-picolyl)-[3.1.3.1] or [3.1.1.1]arenes, can be applied for this purpose. The 4-picolyl group can form covalent bonds with alkylation and form coordination bonds with a variety of transition metal ions. By using these bonds, we extend the cavity size of the azacalixarenes and construct newly designed supramolecular structures. We expected that these molecules would form larger molecular cavities upon side arm modification, and inclusion abilities of these cavities can be extended compared to the azacalixarenes of small cavity sizes. However, most of these molecular structures could not be determined, and none showed inclusion phenomena contrary to our expectations. Only the molecular structure of a p-xylylene-bridged molecule was confirmed, which possessed a self-inclusion structure in which the bridging unit (p-xylylene) was encapsulated by two azacalixarene cavities. Additionally, it was found that p-methyl-N-(4-picolyl)azacalix[3.1.1.1]arene 1 formed two molecular packing modes depending on the recrystallizing solvents. One is stacked structure by π–π interactions, and another is capsule type structure in which two solvent molecules were encapsulated. A self-inclusion type cage molecule was obtained by connecting N-(4-picolyl)azacalix[3.1.1.1]arene with a p-xylylene unit.
Databáze: OpenAIRE
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