Bidirectional association of branched noncovalent complexes of tetrazoles and 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene in solution

Arno Kraft, Frank Osterod, Roland Fröhlich

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57 Citations (Scopus)

Abstract

Noncovalent 3:1 complexes were obtained by combining acidic tetrazoles with the tribasic 1,3,5-tris(4,5-dihydroimidazol-2-yl)benzene (1). A branched structure and the use of solubilizing groups ensured that the resulting complexes dissolved in a range of nonpolar organic solvents. An X-ray crystal structure analysis of a model complex with tetrazole showed a completely planar, C3-symmetrical, hydrogen-bonded molecule that salt-packed along the crystallographic c axis with an interplanar spacing of 3.31 Å. Model binding studies between a tetrazolate and a protonated 1,3-bis(4,5-dihydroimidazol-2- yl)benzene allowed an association constant of 2470 ± 400 M-1 to be measured in the competitive solvent mixture CDCl3/CD3OD (97:3). The ionic nature and the extended planarity of the tetrazole complexes' core favored the formation of supramolecular stacks not only in the solid, but also in (nonpolar) solution. Self-association was evidenced by NMR and CD spectroscopy as well as by vapor-pressure osmometry.

Original languageEnglish
Pages (from-to)6425-6433
Number of pages9
JournalJournal of Organic Chemistry
Volume64
Issue number17
DOIs
Publication statusPublished - 20 Aug 1999

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