4`-Hydrazone derivatives of 2,2`: 6`,2``-terpyridine : protonation and substituent effects
JournalArticle (Originalarbeit in einer wissenschaftlichen Zeitschrift)
ID 43263
Author(s) Beves, Jonathon E.; Constable, Edwin C.; Housecroft, Catherine E.; Neuburger, Markus; Schaffner, Silvia; Zampese, Jennifer A.
Author(s) at UniBasel Constable, Edwin Charles
Housecroft, Catherine
Year 2008
Title 4`-Hydrazone derivatives of 2,2`: 6`,2``-terpyridine : protonation and substituent effects
Journal European Journal of Organic Chemistry
Volume 2008
Number 20
Pages / Article-Number 3569-3581
Keywords hydrazone, protonation, rotamers, 2,2': 6',2 ''-terpyridine
Abstract Four 4`-hydrazone derivatives of 2,2`:6`,2 ``-terpyridine which vary in their N- and C-substitution in the R`NN=CRPh unit have been prepared and structurally characterized. Protonation studies and solution behaviour of these compounds are described, as well as representative crystal structures of mono- and diprotonated derivatives. In the solid-state structures of each neutral compound, the tpy domain adopts the anticipated trans, trans- conformation, and intramolecular steric factors compete with pi-stacking effects to control the amount to which the C-phenyl substituent twists out of the plane of the tpy unit. When R` = H, the imine NH group engages in hydrogen bonding interactions in the solid state, except where R = Ph. In solution, variable temperature H-1 NMR spectroscopy shows that on going from R = Me to Ph (with R` = H), the barrier to rotation about the Cpy-Nimi_ bond increases; with R = R` = H, the hydrogen bonding capabilities of the solvent to the imine NH influence this dynamic process. In the N-methyl derivative (R = H and R` = Me), rotation about the C-py-N-imine bond is facile at room temperature. Protonation of the derivative with R = R` = H results in an increase in the activation barrier to rotation, consistent with a greater pi-contribution to the C-py-N-imine bond.
Publisher Wiley
ISSN/ISBN 1434-193X ; 1099-0690
edoc-URL http://edoc.unibas.ch/dok/A5248852
Full Text on edoc No
Digital Object Identifier DOI 10.1002/ejoc.200800301
ISI-Number 000257826600021
Document type (ISI) Article

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