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Issue 39, 2017
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Syntheses of metallo-pseudorotaxanes, rotaxane and post-synthetically functionalized rotaxane: a comprehensive spectroscopic study and dynamic properties

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Abstract

Herein, a bis-amido tris-amine macrocycle and five bipyridine-based bidentate chelating ligands were investigated towards various divalent transition metal ion (NiII, CoII, CuII, and ZnII)-templated syntheses of metallo [2]pseudorotaxanes. The formation of these ternary complexes was elucidated via different spectroscopic techniques such as ESI-MS, absorption spectroscopy, EPR spectroscopy, and single-crystal X-ray diffraction studies wherever possible. Azide-terminated NiII, CoII, CuII, ZnII-templated [2]pseudorotaxanes were explored to generate [2]rotaxane, ROT, via reaction with an alkyne-terminated triphenylene unit as a stopper under the mild reaction condition of the CuI-catalyzed azide–alkyne cycloaddition reaction. NiII-templated [2]pseudorotaxane was found to be the best precursor towards the high-yield synthesis of ROT. The interpenetrative nature of the center piece in metal-free rotaxane was also established through various spectroscopic techniques such as ESI-MS and 1D and 2D (COSY, NOESY, ROESY, and DOSY) NMR spectroscopy. Furthermore, ROT was functionalized via tri-acetylation as AcROT to incorporate three tertiary amides at the tris-amine centers; this AcROT exhibited rotamer-induced molecular motions in an interpenetrated system via the formation of multiple conformers/co-conformers. Additionally, the existence of multiple rotamers was established via variable-temperature NMR spectroscopic studies. Li+ and 12-crown-4 were found to be suitable for the reversible conformation/co-conformation fixation of tri-acetylated bis-amido tris-amine macrocyclic wheel-based rotaxane.

Graphical abstract: Syntheses of metallo-pseudorotaxanes, rotaxane and post-synthetically functionalized rotaxane: a comprehensive spectroscopic study and dynamic properties

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Publication details

The article was received on 14 Apr 2017, accepted on 20 Jul 2017 and first published on 20 Jul 2017


Article type: Paper
DOI: 10.1039/C7DT01364G
Citation: Dalton Trans., 2017,46, 13300-13313
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    Syntheses of metallo-pseudorotaxanes, rotaxane and post-synthetically functionalized rotaxane: a comprehensive spectroscopic study and dynamic properties

    S. Santra, S. Bej, M. Nandi, P. Mondal and P. Ghosh, Dalton Trans., 2017, 46, 13300
    DOI: 10.1039/C7DT01364G

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