Syntheses, crystal structure, electrochemistry and luminescence properties of lanthano- germanotungstates

A series of sandwich-type early lanthanoid substituted complexes: [Ln(alpha-GeW11O39)(2)](13-) [Ln = La-III (La-1) and Ce-III (Ce-2)] and acetate-bridged hybrid dimeric complexes: [{Ln(mu-CH3COO)GeW11O39(H2O)}(2)](12-) [Ln = Pr-III (Pr-3), Nd-III (Nd-4) and Sm-III (Sm-5)] were synthesized by the interaction of a trilacunary Na-10[GeW9O34]center dot 18H(2)O precursor with Ln(NO3)(3)center dot nH(2)O in a potassium acetate buffer at pH 4.7. All these compounds were isolated as mixed sodium/potassium salts and structurally characterised by various analytical techniques such as single-crystal X-ray diffraction, FT-IR, ICP-AES, UV/vis, photoluminescence spectroscopy, thermogravimetric analysis, C-13 and H-1 NMR spectroscopy, magnetism and electrochemistry. The FT-IR spectra suggest that compounds (La-1a and Ce-2a) and (Pr-3a-Sm-5a) are isomorphous. We also synthesized analogous acetate-bridged dimeric complexes (Pr-3a to Sm-5a) with mid and late lanthanoid ions (Ln = Eu-III, Gd-III, Tb-III, Dy-III, Ho-III, Er-III, Tm-III and Yb-III) using a procedure published elsewhere and also investigated other features such as electrochemistry and magnetic and photochromic properties. The molecular complexes Pr-3a, Sm-5a, Eu-6a, Tb-8a, Dy-9a, Ho-10a, Er-11a and Tm-12a show good photochromic behaviour at room temperature. Magnetic studies of La-1a, Ce-2a, Pr-3a, Nd-4a and Sm-5a were performed at room temperature and the molecular complexes were found to exhibit ferromagnetic behaviour.