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The IzattâChristensen Award in Macrocyclic and Supramolecular Chemistry: A 25-Year History (1991â2016)
Reed M. Izatt,1,2 Jerald S. Bradshaw,1,2 Steven R. Izatt,1 and Roger G. Harrison2
1 IBC Advanced Technologies, Inc., American Fork, UT, USA
2 Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
1.1 Introduction
The IzattâChristensen Award (IâC Award) recognizes excellence in macrocyclic and supramolecular chemistry. It has been presented annually since 1991 by the International Symposium on Macrocyclic and Supramolecular Chemistry (ISMSC). A common theme to both of these fields is molecular recognition. The search for underlying principles governing molecular recognition or how molecules recognize each other began in earnest in the early 1960s. Working independently, several individuals who later became prominent in the emerging fields of macrocyclic chemistry and supramolecular chemistry, made important early contributions to molecular recognition. Four of these were Charles J. Pedersen (1904â1989), Daryle H. Busch, Jean-Marie Lehn, and Donald J. Cram (1919â2001). Prior to the 1960s, no concentrated effort had been made to investigate chemical selectivity involving macrocyclic compound interactions with metal ions or other guest molecules [1] .
Charles Pedersen while employed at du Pont serendipitously discovered the compound that later came to be known as dibenzo-18-crown-6 (DBl8C6). Pedersen isolated DBI8C6 in a 0.4% yield from a âbrownish gooâ while attempting to prepare a completely different compound[2]. The decision to expend the effort needed to isolate, purify, and characterize the compound that became known as DBl8C6 represents a true example of scientific creativity and luck. The story of Pedersenâs discovery, reported in 1967, his identification of the many new cyclic polyether macrocyclic compounds he synthesized, his characterization of their selective complexation with alkali metal ions, and his own account of the events surrounding the discovery make fascinating reading [2, 3].
Daryle Busch remembers that his first ideas of synthesizing macrocycles occurred while a graduate student with John Bailar at the University of Illinois in the early1950s. His account of these first ideas of forming macrocycles from bidentate amines involved in copper(II) chelation illustrates the workings of a creative mind. It was several years later in 1962, as a Professor of Inorganic Chemistry at Ohio State University, that he reported the first synthesis of a macrocycle using a metal template [1, 5] He received the IâC Award in 1994 and is the author of a chapter in this book [4], in which he gives a first-hand account of his work.
Jean-Marie Lehn reported the synthesis of macrobicyclic polyethers containing three polyether strands joined by two bridgehead nitrogen atoms [6] in 1969, shortly after Pedersenâs initial paper. Lehn later coined the term, âsupramolecular chemistry,â to describe the broadening of the scope of hostâguest chemistry which he and his research group had spearheaded [7]. To quote Professor Lehn, âBeyond molecular chemistry, supramolecular chemistry aims at constructing highly complex, functional chemical systems from components held together by intermolecular forces.â These components can be visualized as hostâguest systems bonded by intermolecular forces, which are much weaker than covalent chemical bonds. The guest systems may include organic guests as well as metal ions. The number and variety of hosts synthesized has expanded far beyond macrocyclic compounds. Lehn has provided an account of his early work [7].
Donald Cram was a prominent organic chemist in the 1960s. John Sherman [8], one of his Ph.D. students, describes him as âdefinitely old school. Eccentric. Hard driven. Strong-willed. Spirited. Fearless.â Cramâs accomplishments included a major research program in organic chemistry, co-author of three major organic chemistry textbooks, and instructor at UCLA of several generations of organic chemistry students. His first acquaintance with macrocyclic chemistry was recorded by Roeland Nolte who remembers [9] that during a stay as a visiting scientist in Cram...