Mapping the synthesis of low nuclearity polyoxometalates from octamolybdates to Mn-Anderson clusters

Abstract

A comprehensive study of the isomer-independent synthesis of TRIS ((HOCH(2))(3)CNH(2)) Mn-Anderson compounds from Na(2)MoO(4)·2H(2)O, via the corresponding octamolybdate species, is presented. Three octamolybdate salts of [Mo(8)O(26)](4-) in the β-isomer form, with tetramethylammonium (TMA), tetraethylammonium (TEA) and tetrapropylammonium (TPA) as the counter cation, were synthesised from the sodium molybdate starting material. Fine white powdery products for the three compounds were obtained, which were fully characterised by elemental analysis, TGA, solution and solid state Raman, IR and ESI-MS, revealing a set ratio of Na and organic cations for each of the three compounds; (TMA)(2)Na(2)[Mo(8)O(26)] (1), (TEA)(3)Na(1)[Mo(8)O(26)] (2) and (TPA)(2)Na(2)[Mo(8)O(26)] (3), and the analyses also confirmed that the three compounds all consisted of the octamolybdate in the β-isomeric form. ESI-MS analyses of 1, 2 and 3 show similar fragmentation for these β-isomers compared to the previously reported study for the α-isomer ((TBA)(4)[α-Mo(8)O(26)]) (A) in the synthesis of ((TBA)(3)[MnMo(6)O(18)((OCH(2))(3)CNH(2))(2)]) (B), and compounds 1, 2 and 3 were successfully used to synthesise equivalent TRIS Mn-Anderson compounds: (TMA)(3)[MnMo(6)O(18)((OCH(2))(3)CNH(2))(2)] (4), (TEA)(3)[MnMo(6)O(18)((OCH(2))(3)CNH(2))(2)] (5) and (TPA)(2)Na(1)[MnMo(6)O(18)((OCH(2))(3)CNH(2))(2)] (6), as well as Na(3)[MnMo(6)O(18)((OCH(2))(3)CNH(2))(2)] (7). This is the first example where symmetric organically-grafted Mn-Anderson compounds have been synthesised in DMF from anything but the {Mo(8)O(26)} α-isomer.

The Anderson–Evans polyoxometalate: From inorganic building blocks via hybrid organic–inorganic structures to tomorrows “Bio-POM”

“…The six protons on the μ 3 -O atoms surrounding the Mn III heteroatom on both sides are replaced by the tris-ligands giving the δ-isomer ( Figure 4B) [86]. Rosnes et al [178] showed that both isomers [α-Mo 8 [179,180] can be used to synthesize hybrid organic-inorganic Mn III Mo 6 compounds. The β-isomer is shown in the upper left corner in Figure 7 and the α-isomer differs by incorporating two tetrahedra instead of the two central octahedra on each side.…”

“…The β-isomer is shown in the upper left corner in Figure 7 and the α-isomer differs by incorporating two tetrahedra instead of the two central octahedra on each side. The reaction media can also be exchanged with DMF making it possible to use ligands that are not soluble in acetonitrile and the desired cations may be directly introduced, even small inorganic cations [178]. Since then symmetric post-functionalization (Figure 7, A3) has been achieved with a variety of organic ligands including ligands containing aromatic units [181] and alkyl-chains [182] of different lengths (see section 5.2).…”

The Synthesis and Characterization of Aromatic Hybrid Anderson–Evans POMs and their Serum Albumin Interactions: The Shift from Polar to Hydrophobic Interactions

“…Fe 3 + and Mn 3 + were chosen as templating heteroatoms because both provide POM hybrids in good yields (86 %b ased on Mo). [38] Compounds TBA-FeMo 6 -bzn, TBA-FeMo 6 -cin, TBA-MnMo 6 -bzn,a nd TBA-MnMo 6 -cin were obtained by heating Fe(acac) 3 or Mn(OAc) 3 ,( TBA) 4 [a-Mo 8 O 26 ], and bzn or cin at reflux in acetonitrile for 18 h( Scheme 1d). All four compounds were isolated as TBA salts with poor water solubility (< 3mm).…”

“…The bond lengthso ft he three different bindingm odes are summarized in Table 2a nd are in good agreement with other TRIS-functionalized Anderson POMs. [28,38] The organicl igands are grafted directly onto the oxygen atoms that surround the heteroatom (Figure 1).…”

Immobilization of Polyoxometalates on Tailored Polymeric Surfaces

“…This well-known class of nanosized anionic nanoclusters with metal-oxo frameworks offers outstanding features, such as (i) possessing high solution, thermal, and oxidative stability; (ii) including species with a wide range of well-defined sizes and shapes, often with highly symmetric topologies; (iii) having interesting electronic properties (e.g., storage of multiple electrons/protons without substantial skeletal modifications) that can be tuned to a great extent by systematic compositional variations on the POM frameworks; (iv) acting as multidentate inorganic ligands to incorporate either organic moieties with additional functionalities or extra d- or f-block metallic centers [5,6,7,8,9,10]. These features have allowed POMs to find potential applications in diverse fields (e.g., catalysis, magnetism, biomedicine, spintronics, molecular recognition, optics, conductivity, ion exchange) with implications in current issues of interest related to technology, health, energy, and the environment [11,12,13,14,15]. As inorganic components, POMs have, for example, been combined with amphiphilic molecules or cationic surfactants to construct several discrete architectures (micelles, capsules, vesicles, cones), fibers and wires, or highly ordered bidimensional arrays (self-assembled monolayers, Langmuir and Langmuir–Blodgett films, layer-by-layer structures) [16,17,18,19,20,21,22,23].…”