Conformational mobility of 7,16-bis(4-methoxybenzyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane in molecular and proton-transfer complexes: X-ray and DFT studies

For the first time the bibracchial-crown ether7, 16-bis(4-methoxybenzyl)-1, 4, 10, 13-tetraoxa-7, 16-diazacyclooctadecane (1) and its molecular and proton-transfer complexes were isolated and characterized by X-ray single-crystal diffraction. Hydrogen bonding between the neutral molecules is present...

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Bibliographic Details
Published in:New journal of chemistry 2009, Vol.33 (8), p.1646-1656
Main Authors: Fonari, Marina S., Ganin, Eduard V., Chumakov, Yurii M., Botoshansky, Mark M., Suwinska, Kinga, Basok, Stepan S., Simonov, Yurii A.
Format: Article
Language:English
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Summary:For the first time the bibracchial-crown ether7, 16-bis(4-methoxybenzyl)-1, 4, 10, 13-tetraoxa-7, 16-diazacyclooctadecane (1) and its molecular and proton-transfer complexes were isolated and characterized by X-ray single-crystal diffraction. Hydrogen bonding between the neutral molecules is present in the binary complex 1 times (H sub(2)NCS) sub(2) (3) giving rise to a tape structure. The proton migration from an inorganic acid to a macrocyclic molecule results in doubly protonated cations (1-H sub(2)) super(2+) and (2-H sub(2)) super(2+) (where 2 is the parent 7, 16-dibenzyl-1, 4, 10, 13-tetraoxo-7, 16-diazacyclooctadecane) giving rise to the ionic complexes (1-H sub(2)) times [CIO sub(4)] sub(2) times 2H sub(2)O (4), (1-H sub(2)) times [NbF sub(6)] sub(2) times 2H sub(2)O (5), (1-H sub(2)) times [TaF sub(6)] sub(2) times 2H sub(2)O (6), (1-H sub(2)) times [BF sub(4)] sub(2) (7) and (2-H sub(2)) times [CIO sub(4)] sub(2) times 2H sub(2)O (8) sustained by a system of charge-assisted hydrogen bonding. The macrocyclic entities in 1-8 differ by the conformation of the crown ring and the arrangement of the pendant arms. To rationalize the different conformations of 1 in comparison with the relative compounds based on 2, the theoretical quantum chemical calculations on the DFT (B3LYP) level were performed. The contribution of the methoxy group that provides the C-H super(...)O(OCH sub(3)) hydrogen bonding to the overall system of intermolecular interactions has been estimated by comparison with the complexes based on 2.
ISSN:1144-0546
1369-9261
DOI:10.1039/b902953b