Síntesis y evaluación de la capacidad complejante de ligandos nitrogenados derivados de bifenilos sustituidos.

Abstract

Design and preparation of sensor molecules for cations, anions or neutral molecules has always been an attractive challenge in Supramolecular Chemistry. A sensor molecule is a molecule which is able to recognise a defined substrate and is due to report, somehow, that this recognition has been occurred by means of a change in a physic or chemical property, which can be macroscopically measured. In this thesis, fifteen new sensor molecules have been developed. Variation in the emission of fluorescence is used as indicator in the detection of defined cations and anions. All these molecules are based in a biphenyl-derivated moiety, which contains NO2 or N(CH3)2 (tetramethylbenzidine, TMB) groups in the 4,4 positions. Subunits that are responsible of the recognition are placed in the 2,2 positions and can be either azacrown ethers or polyethylenamine chains (podands). In this work, both synthesis and studies (photochemical, electrochemical, determination of the stoichiometry of the formed complexes and calculations of the complexation constants) of the efficient behaviour of these molecules in the recognition of different alkaline, earth-alkaline, transition and post-transition metal cations are reported. It has also been studied the ability of some molecules in the detection of anions (F-, Cl-, Br-, HSO4-, H2PO4-, NO3-). For the TMB-derivated ligands, intensity in the emission of fluorescence is in strong dependence on the dihedral angle between biphenyl rings. Ability of some of the nitroderived molecules as carriers of different alkaline and earth-alkaline picrate salts across a chloroformic membrane has been evaluated, obtaining high transport rates. Finally, an electrochemical modulation in the a ffinity of some of the previously nitroderived compounds for the toxic metal cation Zn2+ and Cd2+ has been found out.