The 1074th General Monthly Meeting
The Annual Liversidge Research Lecture
New Molecular Receptors for Small Molecules and Ions
Professor L.F. Lindoy
School of Chemistry
University of Sydney
Date: Wednesday, 1st July, 1998
Location: University of Sydney
ABSTRACT
Stepwise synthetic strategies with a "building block" approach have been employed to produce new supramolecular receptors incorporating macrocycles as structural elements. The host-guest complexation behaviour of these species with both metal cations and organic guests has been investigated using a range of physical and computational techniques. Emphasis in these studies has been given to the development of systems showing selective host-guest complexation behaviour.
Report on the Lecture
Dr Edmund PotterVice-President
"Holecules on their Metal"
Professor Lindoy, a leading coordination chemist in the modern vein, spoke with admirable lucidity on the topic New Molecular Receptors for Small Molecules and Ions.
Nowadays, it's schoolboy chemistry to hear that (for example) the solvent cyclohexane, C6H12, has its six carbon atoms arranged in a regular hexagonal ring with the tiny hydrogen atoms bonded symmetrically in pairs to each carbon atom. The unoccupied space inside the ring is too small to permanently enclose any other atomic species. Such is not the case with the much larger carbon rings that Professor Lindoy and his associates have been fashioning and studying for the past decade.
As he illustrated, 14-17-membered rings have space centrally to accomodate the ions of familiar metals like lead, zinc, cadmium, nickel and silver. Although whimsically one may call such molecules "holecules", a reliable rationale is still sought for predicting whether any one type of ring will offer stable coordination to any particular metal.
Instead, a variety of experimentally-based structural indicators have been developed using the Stability Constant (normally logK) to order the database. This is particularly useful for gauging the specific coordinating influences of substituents (S, N, NH, CH3, etc) in and on the ring, taking into account ring size and central cage shape and magnitude. The speaker described various examples where contrasts in coordination stability were large, allowing otherwise difficult metal separations to be achieved.
Professor Lindoy authoritatively answered many questions from his audience before Professor Field proposed a vote of thanks to which all responded enthusiastically.