Synthesis, Crystal Structure and Physico‐Chemical Studies of Neodymium and Erbium Methoxides Containing Thienyl Substituents

Abstract

Abstract Two novel mononuclear neodymium alkoxides [Nd{OC(C 14 H 11 S 2 )} 3 (thf) 3 ] · thf ( 9 ) and [Nd{OC(C 16 H 13 S)} 3 (thf) 3 ] · thf ( 10 ) have been prepared by the reaction between Nd[N(SiMe 3 ) 2 ] 3 and the tertiary alcohols HO–C(C 14 H 11 S 2 ) ( 3 ) and HO–C(C 16 H 13 S) ( 4 ). The geometry around the neodymium metal is almost octahedral with a facial ligand arrangement similar to [Nd{OC(C 8 H 5 S 2 ) 3 } 3 (thf) 3 ] · 4thf ( 5 ), [Nd{OC(C 4 H 3 S) 3 } 3 (thf) 3 ] · thf ( 7 ) and Er[OC(C 4 H 3 S) 3 ] 3 (thf) 3 ( 8 ) (X‐ray diffraction on single crystals). The cyclic voltammograms of a series of neodymium and erbium alkoxides indicate that the electrochemical properties are essentially dominated by the organic ligands. In comparison to the carbinols HO–C(C 8 H 5 S 2 ) 3 ( 1 ), HO–C(C 4 H 3 S) 3 ( 2 ), HO–C(C 14 H 11 S 2 ) ( 3 ) or HO–C(C 16 H 13 S) ( 4 ), the oxidation peak potentials of the thienyl units for the neodymium alkoxides [Nd{OC(C 8 H 5 S 2 ) 3 } 3 (thf) 3 ] · 4thf ( 5 ), [Nd{OC(C 4 H 3 S) 3 } 3 (thf) 3 ] · thf ( 7 ), [Nd{OC(C 14 H 11 S 2 )} 3 (thf) 3 ] · thf ( 9 ) and [Nd{OC(C 16 H 13 S)} 3 (thf) 3 ] · thf ( 10 ) are marginally shifted towards higher values by 0.03–0.10 V, whereas for Er[OC(C 8 H 5 S 2 ) 3 ] 3 (thf) ( 6 ) and Er[OC(C 4 H 3 S) 3 ] 3 (thf) 3 ( 8 ) a decrease of these potentials is noticed. Repetitive cyclic voltammetry does not generate polymeric films for 7 – 10 , as found for the free organic ligands 2 – 4 . Contrarily, the mononuclear precursors [Nd{OC(C 8 H 5 S 2 ) 3 } 3 (thf) 3 ] · 4thf ( 5 ) and Er[OC(C 8 H 5 S 2 ) 3 ] 3 (thf) ( 6 ) are electro‐oxidized and electro‐active polymer films are obtained and characterized. To investigate the positions of the excited states of the ligands, emission spectra of the carbinols 1 – 4 have been recorded. The luminescence studies of the neodymium alkoxides reveal an energy transfer from the ligand to the metal centre with a remarkable Nd emission efficiency upon ligand excitation in the case of 5 .