Co-conformational mechanoisomerism in a calix[6]arene-based [2]rotaxane

ABSTRACT

The synthesis of a [2]rotaxane, comprising a calix[6]arene-wheel and a dibenzyl-ammonium axle, is here reported. By virtue of its inherent directionality, the calix-wheel makes non-degenerate two equivalent stations of the symmetrical axle. In this way, the neutral rotaxane shows two co-conformations, named endo-alkyl and endo-benzyl, in which an alkyl or benzyl moiety of the axle are included inside the calix-cavity, respectively. NMR and DFT studies showed that the co-conformation preferred by the neutral mechanomolecule is the ‘endo-alkyl’ one, which is more stabilized by C-H···π interactions between the included alkyl chain and the aromatic wall of the calix-cavity.

Graphical Abstract

KEYWORDS:

• Calixarene
• rotaxane
• co-conformer
• mechanoisomerism
• Density Functional Theory

Acknowledgments

The authors acknowledge the Regione Campania (POR CAMPANIA FESR 2007/2013 O.O.2.1, CUP B46D14002660009) for the FT-ICR mass spectrometer facilities, Farma-BioNet (CUP B25C13000230007), the Centro di Tecnologie Integrate per la Salute” (CITIS) (project PONa3_00138) for the 600 MHz NMR facilities and Università di Salerno for financial support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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