Syntheses, Crystal Structure and Physico-Chemical Studies of Sodium and Potassium Alcoholates Bearing Thienyl Substituents and their Derived Luminescent Sm(III) Alkoxides
Résumé
The synthesis, structural characterization, electrochemistry and luminescence properties of a series of alkali metal alcoholates and Sm(III) alkoxides with thiophene−based−OR substituents are presented. The alkali metal alcoholates 7-15 have been obtained by deprotonation of the carbinol with NaH or KH. Their molecular structures consist of tetranuclear alkali metal alcoholates with a distorted cubane−like M4O4 core (X-ray structure analyses). Each alkali metal is surrounded by three carbinolate ligands and (depending on the derivative) by additional tetrahydrofuran molecules. The mononuclear samarium alkoxides {Sm[OC(C4H3S)3]3(thf)3} * thf (16) and {Sm[OC(C16H13S)]3(thf)3} * thf (17) were synthesized by the salt metathesis reactions between {[KOC(C4H3S)3]4(thf)2} * thf (7), [NaOC(C4H3S)3]4(thf)2 (8) or {[KOC(C16H13S)]4(thf)3} * ½ thf (11), respectively, and SmCl3 in thf solution. The molecular structures of these air−sensitive base adducts have been determined by single−crystal X−ray crystallography and reveal an approximately octahedral coordination sphere around the samarium metal centres with three methoxido ligands and three facially arranged thf molecules. The electrochemical properties are essentially dominated by the oxidation of the thienyl units. The emission spectra of the carbinols and their derived potassium and sodium compounds display broad bands attributed to the π*→π transitions of the aromatic ligands. Luminescence studies performed on complexes 16 and 17 reveal the typical f−f transitions of the Sm(III) ion. The photophysical data suggest that an energy transfer from the ligand to the metal centre operates.
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