Bermejo Patiño

GRUPO DE INVESTIGACIÓN DEL CIQUS DURANTE 2011-2015

FUNCTIONAL HELICATES

Supramolecular helicates are a special class of metal complexes in which two or more ligands wrap around the axis defined by two or more metal centres. Hundreds of examples and several reviews on these compounds and their properties have been published since their introduction into the scientific literature by Lehn et al. in 1987.

Besides the intrinsic importance that helicates have in the study of self-assembly processes directed by metal ions, there is great interest in finding functional applications for this class of compounds and this is motivated by the unique chemical and physical properties arising from their special structural features.

Our research group is pioneer in the design and study of these novel systems. We show two different examples of metal helicates with potential applications in the magnetic and the catalysis field.

ENDOGENOUS ARENE HYDROXYLATION PROMOTED BY COPPER(I) CLUSTER HELICATES

We have reported the first example of a hexanuclear Cu(I) cluster helicate. In solution, this complex has the practical application of promoting an endogenous arene hydroxylation process. The kinetic studies for the hydroxylation reaction showed a ΔH⁼ value of around -70 kJ/mol, which is similar to those found for the hydroxylations mediated by tyrosinase.

This approach could open new perspectives for the design of functional helicates with catalytic activity.

EXTENDED SUPRAMOLECULAR ARCHITECTURES

We are also interested in obtaining new types of extended supramolecular arrays, by using conveniently functionalized small supramolecular units and applying the “sequential self-organization strategy”.

We strongly believe that this approach could open new perspectives for the spontaneous, but controlled, generation of large organized arrays with the aim of obtaining new functional nanomolecular architectures.

METALLO-SUPRAMOLECULAR HELICAL ENTITIES WITH TUNABLE MAGNETIC PROPERTIES

Our group has established a method to modulate the strength of the superexchange coupling interaction in dinuclear helical assemblies based on the coordination preferences of the metal centres. The appropriate choice of metal centres with different preferential coordination geometries allows the modulation of the strength of the magnetic exchange in a double-stranded dinuclear helical assembly.

Thus, the reduced distance between the metal centres in [Ni^II₂(L)₂] compared with that in [Cu^II₂(L)₂], and the existence of a new electronic pathway between them through the pyridine bridges lead to an enhancement of the intramolecular metal-metal superexchange coupling in the nickel helicate.

This is first example of a metallo-supramolecular helical entity with tunable magnetic properties. We believe that this approach could open new perspectives for programming magnetic devices and materials based on helicates.