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.

Structure, Formation, and Dynamics of Mo12 and Mo16 Oxothiomolybdenum Rings Containing Terephtalate Derivatives

“…The latter exhibits dynamic behavior, consistent with the gliding of both the stacked aromatic groups. Stability and dynamics of both Mo 16 rings was related to weak hydrophobic or p-p stacking inter-template interactions and inner hydrogen-bond network occurring within the [Mo 16 -A C H T U N G T R E N N U N G (IsoP) 2 ] 4À and [Mo 16 A C H T U N G T R E N N U N G (PDA) 2 ] 4À ions.…”

“…2 + system led only to a single compound, the [Mo 16 A C H T U N G T R E N N U N G (PDA) 2 ] 4À ion. The latter exhibits dynamic behavior, consistent with the gliding of both the stacked aromatic groups.…”

“…2 + system gave rise to equilibrium, involving mono-templated [Mo 12 IsoP] 2À and bis-templated [Mo 16 A C H T U N G T R E N N U N G (IsoP) 2 ] 4À ions.…”

“…Thermodynamic parameters have been determined and showed that the driving-force for the formation of the [Mo 16 A C H T U N G T R E N N U N G (IsoP) 2 ] 4À is entropically governed. However, whatever the conditions (temperature, proportion of reactants), the PDA…”

“…[19,20] This system was shown to be fruitful for developing extended cyclic inorganic clusters, differing in their nuclearity and shape by the nature of the encapsulated substrate, being either mono-or polyphosphates, [21][22][23] metalates, [24][25][26] or polycarboxylates. [27][28][29] The flexible and adaptable cyclic oxothiomolybdenum rings exhibiting an open inner available cavity, display attractive properties for bioin- 16 …”