Influence of metal ions on the structures of Keggin polyoxometalate-based solids: Hydrothermal syntheses, crystal structures and magnetic properties

• Published in: Journal of solid state chemistry 2006-01, Vol.179 (1), p.253-265
• Main Authors: Shi, Zhenyu, Peng, Jun, Gómez-García, Carlos J., Benmansour, Samia, Gu, Xiaojun
• Format: Article
• Language: English
• Subjects: Bicapped Keggin; COBALT COMPLEXES; Condensed matter: structure, mechanical and thermal properties; COPPER COMPLEXES; Cross-disciplinary physics: materials science; rheology; CRYSTAL STRUCTURE; Exact sciences and technology; Growth from solutions; HYDROTHERMAL SYNTHESIS; Inorganic compounds; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; Magnetic polyoxometalates; Materials science; Methods of crystal growth; physics of crystal growth; Miscellaneous; PARAMAGNETISM; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; ZINC COMPLEXES
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2005.09.051

Three new Keggin polyoxometalate (POM)-based compounds linked to 3d metal complexes have been synthesized under hydrothermal conditions: [Cu(phen) 2] 2{[Cu(phen)] 2 [SiMo 12O 40(VO) 2]} ( 1), {[Zn(phen) 2] 2[GeMo 12O 40(VO) 2]}{[Zn(phen) 2(H 2O)] 2 [GeMo 12O 40(VO) 2]}·3H 2O ( 2) and {[Co(phen) 2] 2[PMo 12O 40(VO) 2]}{[Co(phen) 2(OH)] 2 [PMo 12O 40(VO) 2]}·2.5H 2O ( 3) (phen=1,10-phenanthroline). These three compounds present, as building blocks, the bicapped Keggin anions [ XMo 12O 40(VO) 2] ( X=Si, Ge and P). Compound 1 consists of a bicapped Keggin anion [SiMo 12O 40(VO) 2] 2− linked to two [Cu(phen)] + complexes with two [Cu(phen) 2] + countercations. Compound 2 contains two bicapped Keggin anions [GeMo 12O 40(VO) 2] 4−, one linked to two [Zn(phen) 2(H 2O)] 2+ cations and the other one linked to two [Zn(phen) 2] 2+ cations. Compound 3 is a two-dimensional POM-based square network formed by bicapped Keggin anions [PMo 12O 40(VO) 2] 4− connected by [Co(phen) 2] 2+ cations. Discrete bicapped Keggin anions [PMo 12O 40(VO) 2] linked to two [Co(phen) 2(OH)] + cations are located between the layers. The magnetic properties show the presence of antiferromagnetic interactions among the reduced Mo(V) atoms (in the three compounds) plus a paramagnetic contribution from the V(IV) atoms (in 1 and 2). Compound 3 shows, in addition, an antiferromagnetic interaction between the Co(II) and the V(IV) ions directly linked through an oxygen bridge. The low-temperature ESR spectra of compound 3 confirm the presence of the reduced Mo(V) ions and the antiferromagnetic coupling between the Co(II) and the V(IV) ions. Three new Keggin polyoxometalate-based compounds have been synthesized under hydrothermal condition. These three compounds present the bicapped Keggin anions [ XMo 12O 40(VO) 2] ( X=Si, Ge and P) as building blocks. Among the three compounds, compound 3 is a two-dimensional polyoxometalate-based square network formed by bicapped Keggin anions [PMo 12O 40(VO) 2] 4− connected by [Co(phen) 2] 2+ cations. Discrete bicapped Keggin anions [PMo 12O 40(VO) 2] linked to two [Co(phen) 2(OH)] + cations are located between the layers.