The Quest for Relationships between Conformation and Chiroptical Properties: From Solution to Solid State^*

Ernesto Brunet^*, Hussein M.H. Alhendawi, Olga Juanes, and Juan Carlos Rodríguez–Ubis

Departamento de Química Orgánica, Facultad de Ciencias. Universidad Autónoma de Madrid, 28049–Madrid.^*Responsible author: ernesto.brunet@uam.es.

Received July 15, 2009
Accepted September 14, 2009

Abstract

The enormous interest of the late Prof. Ernest Ludwig Eliel for stereochemical problems has led not only to his publication of a impressively long list of papers, books and countless invitations for keynote lectures at conferences, but has stimulated a similar interest in this field among the many who have had the opportunity to work with him. Ernest's seed on one of us turn out in the quest for new relationships between conformation and chiroptical properties. The germ was a simple molecule, cis–3–hydroxythiane S–oxide, that enabled us to show that the specific rotation at any position of its conformational equilibrium is a weighted average of the specific rotation of the individual conformations. We are now currently involved in the challenging task of the controlled building of solid structures from bottom–up approaches. To this end we have covalently attached optically pure phosphonates within the layers of γ–zirconium phosphate leading to chirality at the supramolecular level. We have shown that conformation and chiroptical properties are also strongly intertwined in the solid state.

Keywords: Eliel, chiroptical properties, conformation, zirconium phosphate, laminar materials, supramolecular chirality.

Resumen

El enorme interés por los problemas estereoquímicos de toda índole mostrado por el tristemente desaparecido Prof. Ernest Ludwig Eliel ha dado lugar, no sólo a su larga y notoria lista de publicaciones, libros y conferencias, sino al no menos importante hecho de dejar la huella de su preocupación en muchos de los que tuvimos la enorme suerte de trabajar con él. En este trabajo describimos cómo Ernest sembró en uno de nosotros la necesidad de buscar relaciones entre propiedades conformacionales y quirópticas. La semilla fue una molécula sencilla, el S–óxido del cis–3–hidroxitiano, en la que mostramos que la rotación específica en cualquier posición de su equilibrio conformacional es una media ponderada de la rotación específica de las conformaciones individuales. En el presente estamos dedicados a la construcción de estructuras sólidas. La unión de fosfonatos ópticamente puros entre las capas del γ–fosfato de zirconio da lugar a quiralidad a nivel supramolecular. Hemos mostrado que los términos conformación y propiedades quirópticas también están íntimamente relacionados en el estado sólido.

Palabras clave: Eliel, propiedades quirópticas, conformación, fosfato de zirconio, materiales laminares, quiralidad supramolecular.

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Acknowledgement

This work has been performed under the indirect support of ERCROS–Farmacia S.A. to which we are highly indebted. Unfortunately, we do regret that the financial backing from the Ministry of Science and Education of Spain has just ceased despite the generous grants received in the near past (MAT2002–03243, MAT2006–00570) and the more than reasonable results so far achieved.

References

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Note

^*Dedicated to the late Prof. Ernest Ludwig Eliel in memoriam.