Design, syntheses, and crystal engineering of versatile supramolecular reagents

by Urbina, Joaquin Francis

Abstract (Summary)
Crystal engineering, or non-covalent synthesis in the solid state, requires an

understanding of intermolecular forces, and the hydrogen bond has become a reliable

non-covalent tool in the construction of supramolecular architectures. In the same way

that synthetic chemists refer to a “yield” to quantify a desired product, crystal engineers

typically determine the successful formation of a supramolecular product according to the

frequency or occurrence of preferred intermolecular interactions between molecules

under certain reaction conditions, thus, the supramolecular yield. These non-covalent

reactions can be effectively carried out using supramolecular reagents (SR’s).

A family of ditopic bis-imidazol-1-yl/benzimidazol-1-yl compounds were synthesized

and used as SR’s in combination with a variety of dicarboxylic acids to produce binary

solids in 100% yield through the primary acid···imidazol-1-yl/benzimidazol-1-yl synthons

even in the presence of potentially disruptive intermolecular interactions. We

furthermore noted that secondary C–H···O interactions within and between 1-D chains

were of equal structural importance based upon an analysis of the metrics displayed by

these interactions. The use of these SR’s as ligands with neutrally charged metal

complexes was also investigated.

SR’s containing benzimidazol-1-yl and carboxamide moieties were synthesized and

combined with two different carboxylic acids to make ternary solids through

acid···benzimidazol-1-yl and carboxamide···acid hydrogen bonds using a hierarchical

approach – the best donor-best acceptor, second best donor-second best acceptor

guidelines. These SR’s were also employed as ligands for high-yielding syntheses of

linear metal complexes where neighboring complexes are linked via

carboxamide···carboxamide hydrogen bonds.

Asymmetric SR’s possessing two different N-heterocycles were synthesized and

employed in the construction of ternary supermolecules with a high degree of structural

selectivity and specificity when introduced to two different carboxylic acids. The

stronger acid interacts at the more basic site, while the weaker acid hydrogen-bonds with

the less basic nitrogen atom. Finally, an SR containing three different binding sites was

designed and synthesized with the aim of producing quaternary co-crystals.

Bibliographical Information:


School:Kansas State University

School Location:USA - Kansas

Source Type:Master's Thesis

Keywords:crystal engineering hydrogen bonds supramolecular chemistry yield reagents general 0485


Date of Publication:01/01/2005

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