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Piperazine-based N4-type 16-membered macroheterocycles and their nickel(II) complexes

Vatsadze, Sergey Z.; Krut�ko, Dmitry P.; Blake, Alexander J.; Mountford, Philip

Piperazine-based N4-type 16-membered macroheterocycles and their nickel(II) complexes Thumbnail


Sergey Z. Vatsadze

Dmitry P. Krut�ko

Alexander J. Blake

Philip Mountford


Square-planar diamagnetic nickel(II) complexes 5a and 5b containing 16-membered diamino-diimino ligands were prepared from the corresponding open-chain complexes 2a and 2b via condensation with o-phthalic dialdehyde in methanol. The solid-state structure of the starting complex 2b revealed the cisoid conformation of aryl groups compared to the transoid one found in the case of 2a. At the same time, the cisoid conformation is not retained in acetone solution: rather, the tert-Bu-substituted complex 2b was fully transformed into the trans form whereas its analogue 2aexhibits both cis and transforms in acetone solution. The cisoid conformation was also observed for the cyclic structures 5a and 5b by X-ray analysis and VT NMR experiments. The borohydride reduction of 5a with subsequent cyanide-assisted removal of nickel led to a new 16-membered tetraazamacrocycle 6. Its X-ray structure showed a cisoid conformation supported by two intramolecular hydrogen bonds that was also sustained in solution. VT NMR experiments revealed the degenerative interconvertion of a macrocycle with activation energy ca. 41.9±0.8 kJ/mol.


Vatsadze, S. Z., Krut’ko, D. P., Blake, A. J., & Mountford, P. (2017). Piperazine-based N4-type 16-membered macroheterocycles and their nickel(II) complexes.

Journal Article Type Article
Acceptance Date Jan 30, 2017
Online Publication Date Jun 7, 2017
Publication Date 2017
Deposit Date Jun 9, 2017
Publicly Available Date Jun 9, 2017
Journal Macroheterocycles
Electronic ISSN 1998-9539
Peer Reviewed Peer Reviewed
Volume 10
Issue 1
Pages 98-109
Keywords 16-Membered macroheterocycles, Diamagnetic nickel(II) complexes, Positron emission tomography, X-ray
diffraction, NMR spectroscopy, Conformational analysis
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Publisher URL
Additional Information © 2017 ISUCT Publishing


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