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

• Published in: RSC advances 2015, Vol.5 (121), p.99754-99765
• Main Authors: Gupta, Rakesh, Hussain, Firasat, Behera, J. N., Bossoh, Amoassi Martin, Mbomekalle, Israël Martyr, de Oliveira, Pedro
• Format: Article
• Language: English
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C5RA19726K

A series of sandwich-type early lanthanoid substituted complexes: [Ln(α-GeW 11 O 39 ) 2 ] 13− [Ln = La III ( La-1 ) and Ce III ( Ce-2 )] and acetate-bridged hybrid dimeric complexes: [{Ln(μ-CH 3 COO)GeW 11 O 39 (H 2 O)} 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 [GeW 9 O 34 ]·18H 2 O precursor with Ln(NO 3 ) 3 · n H 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, 13 C and 1 H 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.