A Novel, Tunable Manganese Coordination System Based on a Flexible “Spacer” Unit:  Noncovalent Templation Effects

• Published in: Journal of the American Chemical Society 2001-12, Vol.123 (48), p.11982-11990
• Main Authors: Tabellion, Frank M, Seidel, S. Russell, Arif, Atta M, Stang, Peter J
• Format: Article
• Language: English
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja0114310

The reaction of bis(hexafluoroacetylacetonato)manganese(II) trihydrate (2), an ∼90° corner unit, with flexible linking unit 4,4‘-trimethylenedipyridine (1) allows for the potential formation of three different types of solid-state coordination species:  infinite helical polymers, closed dimeric systems, and infinite one-dimensional polymers. While the un-templated starting material is known to give a coordination helix, the other two possible species can be realized through the selective use of a variety of simple, organic guests:  toluene (3), diphenylmethane (4), cis-stilbene (5), 1,3-diphenylpropane (6), benzyl alcohol (7), nitrobenzene (8), and cyanobenzene (9). When solutions of 1 and 2 are crystallized in the presence of all of these clathrates, the dimeric macrocycles result in all cases, except for that of 6, in which a syndiotactic, wedge-shaped polymer forms. Employing a linker that is less rigid than is typically used in crystal engineering, such as 1, enables the nucleophilic donor subunit to be more than just a simple “spacer”, instead making it an essential, tunable component in the overall crystal lattice. In so doing, a great deal of molecular “information” is lost, but this is compensated for by an in-depth investigation into the weaker host−guest and/or guest−guest interactions, such as nonclassical hydrogen bonding and an assortment of hydrophobic interactions, present in the various systems.