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The synthesis of the first mesogenic donor-acceptor polyoxometalate (POM)-based hybrid is herein described. The structural and electronic properties of the hybrid compound were evaluated through combination of small- and wide-angle X-ray scattering, optical microscopy, electrochemistry and photoluminescence. In the solid state, the compound behaves as a birefringent solid, displaying a lamellar organization in which double-layers of POMs and bis(thiophene)thienothiophene organic donors alternate regularly. Noticeably, the sub-unit organizations in the composite are similar to that observed for the individual POM and organic donor precursors. Photophysical studies show that in the hybrid, the fluorescence of the organic donor unit is considerably quenched both in solution and in the solid state, which is attributed to occurrence of intramolecular charge-separated state.

International audience; The pyridinium salts of 12-tungstophosphoric acid (PyH)(3)[PW12O40]center dot 2CH(3)CN (1) and (PyH)(3)[PW12O40] (2) have been prepared and studied by single crystal and powder X-ray diffraction (XRD) in order to characterize the crystallographic sites occupied by the pyridinium species. The three PyH+ species are located on two unequivalent sites. Two species are linearly H-bonded to the oxygen atoms of the Keggins unit (alpha species), whereas the third one (beta) forms a bent H-bond. In order to determine the infrared bands characterizing each type of pyridinium species in the 1650-1300 cm(-1) range, infrared spectra have been recorded from room temperature to 100 K. They reveal that only a pyridinium species give rise to the unusual splitting of the PyH+ nu 8b and nu 19b modes, whereas beta pyridinium species lead to a classical pyridinium spectrum.

We report the synthesis and characterization of five novel Mo-containing polyoxometalate (POM) bisphosphonate complexes with nuclearities ranging from 4 to 12 and with fully reduced, fully oxidized, or mixed-valent (Mo(V), Mo(VI)) molybdenum, in which the bisphosphonates bind to the POM cluster through their two phosphonate groups and a deprotonated 1-OH group. The compounds were synthesized in water by treating [Mo(V)(2)O(4)(H(2)O)(6)](2+) or [Mo(VI)O(4)](2-) with H(2)O(3)PC(C(3)H(6)NH(2))OPO(3)H(2) (alendronic acid) or its aminophenol derivative, and were characterized by single-crystal X-ray diffraction and (31)P NMR spectroscopy. (NH(4))(6)[(Mo(V)(2)O(4))(Mo(VI)(2)O(6))(2)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·12H(2)O (1) is an insoluble mixed-valent species. [(C(2)H(5))(2)NH(2)](4)[Mo(V)(4)O(8)(O(3)PC(C(3)H(6)NH(3))OPO(3))(2)]·6H(2)O (2) and [(C(2)H(5))(2)NH(2)](6)[Mo(V)(4)O(8)(O(3)PC(C(10)H(14)NO)OPO(3))(2)]·18H(2)O (4) contain similar tetranuclear reduced frameworks. Li(8)[(Mo(V)(2)O(4)(H(2)O))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·45H(2)O (3) and Na(2)Rb(6)[(Mo(VI)(3)O(8))(4)(O(3)PC(C(3)H(6)NH(3))OPO(3))(4)]·26H(2)O (5) are alkali metal salts of fully reduced octanuclear and fully oxidized dodecanuclear POMs, respectively. The activities of 2-5 (which are water-soluble) against three human tumor cell lines were investigated in vitro. Although 2-4 have weak but measurable activity, 5 has IC(50) values of about 10 μM, which is about four times the activity of the parent alendronate molecule on a per-alendronate basis, which opens up the possibility of developing novel drug leads based on Mo bisphosphonate clusters.

While the reaction of [PW11O39]7- towards first row transition metal ions Mn+ under usual bench conditions only leads to monosubstituted {PW11O39M(H2O)} anions, we show that the use of this precursor under hydrothermal conditions allows to isolate a family of novel polynuclear molecular magnetic polyoxometalates (POMs). The hybrid asymmetric [FeII(bpy)3][PW11O39Fe2III(OH)(bpy)2]·12H2O complex (1) contains the dinuclear {Fe(μ-O(W))(μ-OH)Fe} core where one iron atom is coordinated to a monovacant POM while the other is coordinated to two bipyridine ligands. Magnetic measurements indicate that in 1 the FeIII centers are weakly antiferromagnetically coupled (J = -11.2 cm-1, Ĥ = -JŜ1Ŝ2) compared to {Fe(μ-O)(μ-OH)Fe} systems. This is due to the long distance between the iron center embedded in the POM and the oxygen atom of the POM bridging the two magnetic centers but also, as shown by DFT calculations, to the important mixing of bridging oxygen orbitals with orbitals of the POM tungsten atoms. (Hdmbpy)2[FeII(dmbpy)3]2[(PW11O39)2Fe4IIIO2(dmbpy)4]·14H2O (2) (dmby = 5,5’-dimethyl-2,2’-bpy) and H2[FeII(dmbpy)3]2[(PW11O39)2Fe4IIIO2(dmbpy)4]·10H2O (3) represent the first butterfly-like POM complexes. In these species, a tetranuclear FeIII complex is sandwiched between two lacunary polyoxotungstates which are pentacoordinated to two FeIII cations, the remaining paramagnetic centers being each coordinated to two dmbpy ligands. The best fit of the χMT = f(T) curve leads to Jwb = -59.6 cm-1 and Jbb = -10.2 cm-1 (Ĥ = -Jwb(Ŝ1Ŝ2 + Ŝ1Ŝ2* + Ŝ1*Ŝ2 + Ŝ1*Ŝ2*) – Jbb(Ŝ2Ŝ2*)). While the Jbb value is within the range of related exchange parameter previously reported for non-POM butterfly systems, the Jwb constant is significantly lower. As for complex 1, this can be justified considering Few-O distances. Finally, in absence of coordinating ligand, the dimeric complex [N(CH3)4]10[(PW11O39FeIII)2O]·12H2O (4) has been isolated. In this complex, the two single oxo-bridged FeIII centers are very

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