Jan Becher Ph.D.
Dr. Becher's research area includes: organic chemistry and supramolecular chemistry. His research interests include: supramolecular chemistry, heterocyclic chemistry, especially sulfur-containing heterocycles, tetrathiafulvalene chemistry, macrocyclic chemistry, macrocyclic ligands, cyclophanes, rotaxanes and catenanes of donor-acceptor type.Research Background:
The synthesis of macrocycles, cyclophanes, calixarenes and related 2- and 3-dimensional molecular frameworks has been of fundamental importance for the development of supramolecular chemistry and modern synthetic chemistry. An important aspect in this connection is the design and synthesis of molecular structures which include functionalities positioned in a precise geometry. The construction of a molecular device requires a complete organization of the individual components both in space and time.
A majority of synthetic large concave or cage-type molecules are constructed either from arene or azine units, not forgetting the cyclodextrines. Examples of the first type are the calixarenes, veratrylenes and carcerands while the second type includes examples such as macrobicyclic ligands incorporating a variety of heterobiaryl groups, 2,2'-bipyridines etc.
The first type of concave molecules will bind neutral guests while the second type is able to bind metal cations. There are relatively few examples where the individual components in a cage are functional themselves, which is the case when the cage is constructed from tetrathiafulvalene units. Not only will such molecules be redox-active, but with the right architecture they may also be expected to give unique molecular arrangements and crystal structures due to interactions or formation of charge transfer complexes.
We have developed a versatile protocol for incorporation of the redox-active tetrathiafulvalene group into macrocyclic and cyclophane structures. We have made a variety of large redox-active molecular systems based on tetrathiafulvalenes and we are able to routinely make molecular cages with molecular weights up to 3000, using convergent routes with very high yields in each step. Our experience and technique in synthetic macrocyclic chemistry is general and can of course be used for other large molecular systems. We routinely use high dilution syntheses, plasma desorption mass spectrometry, ultra high pressure autoclave etc. The research group currently consists of 4 PhD students, 6 graduate students and 1 postdoc.
In all our projects we are using the stepwise protection/deprotection syntheses in the construction of large molecular structures. The success of this methodology is due to the excellent protection group, as well as to the use of the effective thiolate nucleophiles which, in most cases, result in very high yields in each steps. We have now made numerous examples where the convergent synthetic strategy results in construction of molecular cage molecules of molecular weights > 3000 in only 3 steps from simple starting materials.
Career HighlightsThesis with professor Ole Buchardt, University of Copenhagen, 1966.
Research associate at N. Clauson-Kaas A/S, 1966-68.
Postdoctoral fellow at Synvar Research Institute, Fulbright fellowship, USA, 1968-69.
Assistant professor 1969-89, awarded Dr. Scient. 1986 and appointed Docent (Professor) in 1989 (Odense University).
Received the "Bjerrum Chemistry Award" and gold medal in 1992 for work in organic synthesis and heterocyclic chemistry.
Member of the editorial board, Journal of Heterocyclic Chemistry and The Danish Natural Science Academy.
Appointed Doctor "Honoris Causa" at Université d'Angers, France, October 1998.
J. Becher, Z-T. Li, P. Blanchard, N. Svenstrup, J. Lau, M. B. Nielsen and K. B. Simonsen, Molecular Recognition and Inclusion, A. W. Coleman ed. Kluwer, 1998, 85.
J. Becher, K. B. Simonsen and M. B. Nielsen, "Tetrathiafulvalenes: Building Blocks in Macrocyclic and Supramolecular Chemistry", J Veciana, C. Rovira and D. B. Amabilino eds., Supramolecular Engineering of Synthetic Metallic Materials, NATO ASI Series, Kluwer 1998, 419.
By this Researcher