ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
O21. Scorpiand-Like Macrocycles As Funtional Models For Molecular
Machines. Kinetic And Mechanistic Studies On Molecular Movements
Induced By pH Gradients
C.E. Castillo Gonzalez, a B. Verdejo, b A. Ferrer, a S. Blasco, b J. González, b J. Latorre, c
M.A. Máñez, a M.G. Basallote, a C. Soriano b , E. García-España b
a
Dpto. de Ciencia de los Materiales e Ingeniería Metalúrgica y Química Inorgánica, Univ. de Cádiz, Apdo 40,
Puerto Real, 11510 Cádiz.
b
Instituto de Ciencia Molecular, Univ. de Valencia, Apdo 22085, 46071 Valencia.
c
Instituto de Materiales de la Universidad de Valencia, C/Dr. Moliner 50, 46100 Burjassot, Valencia
e-mail: esther.castillo@uca.es
Biological motors use chemical energy to effect stepwise linear or rotatory motion, and they are essential in
controlling and performing a wide variety of biological funtions. Thus, a genuine molecular machine is involved
in the synthesis and hydrolysis of ATP, and other fascinating example is the flagelar motor that enables bacterial
movements. Interestingly, the movements in both of these biological machines are asociated with gradients in the
concentration of protons.
Despite their interest, the number of examples in which the kinetics of controlled molecular motions of this kind
has been identified in small model molecules is still not large.
The present study is focused on the kinetics and mechanism of formation, decomposition and reorganization
processes associated with pH changes for a series of scorpiand-like complexes. Some DFT studies have been
also made to obtain information about these molecular movements. The systems considered contain a moving
part, whose motion can be reversibly and repeatedly carried out: i.e. they convert the chemical energy into
mechanical work and can be therefore considered as machines operating at the molecular level.
Our results show that molecular movements associated to the changes of pH can be induced in both the ligands
and their metal complexes. Moverover, the kinetics of the formation processes is strongly conditioned by the
charge of reactants and by the steric characteristics of the ligand, which is controlled by hydrogen bond
formation. The results of the theoretical study also help to understand the kinetic results.
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