Hydrogen-bonded aggregates: Imidazole as a hydrogen-bond director with applications toward the design of solid-state materials
The hydrogen-bond directed molecular recognition properties of imidazole have been studied by analyzing individual hydrogen-bond interactions and the associated patterns of hydrogen-bond connectivity found in small molecule crystals structures. The author has confined the studies to the solid state since weak intermolecular interactions and extended aggregates involving many molecules are easily studied in the solid phase. The hydrogen-bonding modes of 30 substituted imidazoles from the crystallographic literature are investigated. The donor and acceptor preferences of the imidazole group are evaluated in terms of its selectivity for specific functional groups and in terms of substituent effects other than hydrogen-bonding that contribute to the observed patterns of association. It was found that imidazole generally acts as both a donor and an acceptor, forming extended chains. The use of cocrystallization as a way to evaluate the recognition properties of unsubstituted imidazole is demonstrated. The selectivity of imidazole in forming intermolecular hydrogen-bonds with guest molecules is studied in the absence of steric constraints and other competing intramolecular interactions. Imidazole forms hydrogen-bond interactions with guest molecules quite selectively and in patterns that reflect the relative hydrogen-bonding abilities of the competing functional groups. Features common to these aggregate structures are presented in the form of hydrogen-bond rules, which provide powerful tools for predicting new solid-state structures. The author shows that imidazolium carboxylate salts of dicarboxylic acids can be used as molecular building blocks to form polar networks of molecules based on two independent sets of strong hydrogen-bond interactions. The crystal structures of 15 salts are reported. A method is presented for categorizing hydrogen-bond motifs in such a way that complex hydrogen-bond patterns can be disentangled, or decoded, systematically and consistently.
- Research Organization:
- Minnesota Univ., Minneapolis, MN (United States)
- OSTI ID:
- 6915071
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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