Synthesis, crystal structure and physico-chemical studies on thienyl-substituted alkoxides of the rare earth metals

Abstract

The present work focuses on the synthesis, crystal structure determination, electrochemical and luminescence studies of thienyl-substituted methoxides of alkali, tin(II) and rare earth metals. The first part is devoted to the synthesis, NMR and crystallographic investigations of the new products. To correlate structural and stereoelectronic effects on the molecular geometry, a series of rare earth metal alkoxides was prepared. The second part deals on the electrochemical properties of the novel compounds. The cyclic voltammograms are dominated by the oxidation wave of the thiophene groups. No reduction or oxidation of the metal centres has been noticed. Contrarily to the other compounds, the repetitive cycling of potentials of HO—C(C8H5S2)3 (1), {Nd[OC(C8H5S2)3]3(thf)3} • 4 thf (10) and Er[OC(C8H5S2)3]3(thf) (11) leads to the formation of electroactive polymeric film. The third part concerns the luminescence properties of the novel compounds. The UV-Vis absorption spectra are dominated by the organic ligands. The emission spectra of the potassium, sodium and yttrium compounds reveal broad bands attributed to the Pi*-Pi transitions of the aromatic ligands. Furthermore, the luminescence spectra of the Nd3+ and Sm3+ alkoxides exhibit an energy transfer ("antenna effect';) from the ligand to the lanthanide centre.