title: Molecular and multidimensional polyoxotungstates functionalized by {Cu(bpy)}2+ groups.
abstract: Five new materials built from polyoxotungstates and Cu(ii) ions as linkers have been synthesized by hydrothermal reactions from a mixture of sodium tungstate, copper chloride and bipyridine. The value of the initial pH, the nature of the heteroelement (P or Si) and of the ligand (2,2'- and/or 4,4'-bipyridine) permit the control of the nature of the polyoxotungstate clusters and their connectivity via the copper ions, and hence the dimensionality of the framework. A single phase has been obtained with silicon as heteroelement at an initial pH of 5, namely the 2D material [SiW(12)O(40)][Cu(2,2'-bpy)(2)](2).10H(2)O (1) with saturated Keggin polyoxotungstates linked by {Cu(2,2'-bpy)(2)}(2+) groups. With phosphorous as heteroelement and at the same initial pH, three different structures have been isolated according to the nature of the ligand. Indeed, the two 1D materials [{Cu(5)(2,2'-bpy)(5)(H(2)O)(HPO(4))(PO(4))}PW(11)CuO(39)].6H(2)O (2) with 2,2'-bpy and [4,4'-Hbpy][{Cu(2)(2,2'-bpy)(2)(4,4'-bpy)(2.5)}PW(11)CuO(39)].16H(2)O (3) with a mixture of 2,2'- and 4,4'-bpy have been characterized, and a coordination polymer with polyoxometalate guests Na(3)[4,4'-Hbpy]{Cu(4)(4,4'-bpy)(8)(H(2)O)(8)}[PW(11)CuO(39)(H(2)O)][PW(10)Cu(2)O(38)(H(2)O)(2)].38H(2)O (4) with 4,4'-bpy has been obtained. Finally, in basic medium (pH = 10) the unprecedented molecular cluster Na(2)[{Cu(8)(2,2'-bpy)(8)}(PW(8)O(31))(2)].15H(2)O (5) has been evidenced. Magnetic studies of compound 2 revealed that the predominant interactions involve only 4 paramagnetic centers, which are interacting within pairs, among the 6 Cu(ii) centers. The chi(M)T=f(T) curve can be fitted using the dinuclear expression appropriate to the HDVV isotropic exchange Hamiltonian H=-JS(1)xS(2), with S(1)=S(2)=(1/2) and J=-105.4 cm(-1), showing strong antiferromagnetic interactions within the two Cu(ii) pairs.
authors.affiliation: Institut Lavoisier, IREM, UMR 8637, Université de Versailles Saint-Quentin, 45 Avenue des Etats-Unis, 78035, Versailles, France.
authors.forename: Laurent
authors.initials: L
authors.lastname: Lisnard
authors.forename: Anne
authors.initials: A
authors.lastname: Dolbecq
authors.forename: Pierre
authors.initials: P
authors.lastname: Mialane
authors.forename: Jérôme
authors.initials: J
authors.lastname: Marrot
authors.forename: Epiphane
authors.initials: E
authors.lastname: Codjovi
authors.forename: Francis
authors.initials: F
authors.lastname: Sécheresse
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D002384:Catalysis; D003300:Copper / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007553:Isotope Labeling; D008024:Ligands; D008280:Magnetics; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011522:Protons; D013055:Spectrophotometry, Infrared; D013696:Temperature; D017973:Tungsten Compounds / Q000737:chemistry*; D000099294:Polyoxometalates
chemical_list: D015082:2,2'-Dipyridyl; D003300:Copper; D008024:Ligands; D009942:Organometallic Compounds; D011522:Protons; D017973:Tungsten Compounds; C102296:polyoxometalate I; D000099294:Polyoxometalates; C025399:sodium tungstate(VI)