Synthesis, characterization and photochemistry of a new heptamolybdate supported magnesium-aqua coordination complex

Abstract

The synthesis, crystal structure, redox characteristics and photochemistry of a new heptamolybdate supported magnesium-aqua coordination complex viz. (hmtH) 2 [{Mg(H 2 O) 5 } 2 {Mo 7 O 24 }]•3H 2 O 1 (hmt = hexamethylenetetramine) is reported. The cyclic voltammogram reveals quasireversible redox behaviour while the degradation of rhodamine B (RhB) by 1 under sunlight irradiation indicates its photocatalytic activity. In the crystal structure of 1,t w o[ M g (H 2 O) 5 ] 2+ units are linked by a µ 2-bridging bidentate heptamolybdate ligand resulting in a heptamolybdate supported magnesium-aqua coordinated dianionic complex [{Mg(H 2 O) 5 } 2 {Mo 7 O 24 }] 2− charge balanced by two (hmtH) + cations. The cations, anions and the lattice water molecules are linked by several hydrogen bonding interactions.

Synthesis, crystal structure and photochemistry of Hexakis(butan-1-aminium) heptamolybdate(VI) tetrahydrate

“…The (Table S1 in Supplementary Information) agree well with reported data. 10,25 Both the unique [Mo 7 O 24 ] 6− units are built up of seven edge sharing {MoO 6 } octahedra, and are very similar to the heptamolybdate first reported for the ammonium salt by Lindqvist. 33 It is interesting to note that the presence of lattice water in 1 is in accordance with our recent structure analysis of several heptamolybdates.…”

“…24 28 The heptamolybdates (Table 1) in which organic ammonium cations charge balance the [Mo 7 O 24 ] 6− ion exhibit interesting photochemistry. 10,11,13,25,30,31 A survey of the reported synthetic protocols reveals that heptamolybdates are synthesized by a direct reaction of the commercially available (NH 4 ) 6 [Mo 7 O 24 ]•4H 2 O or MoO 3 with an organic amine or an appropriate metal containing reagent. Although some syntheses were performed under hydrothermal conditions 12…”

Self‐Activation of Inorganic‐Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para‐Phenylenediamine Enables Very High Lithium‐Ion Storage Capacity

“…Pure polyoxomolybdates [Mo 7 O 24 ] 6− and [Mo 8 O 26 ] 4− show redox activity and are readily available through acidifying an aqueous molybdate solution [9] . Particularly, the heptamolybdate anion [Mo 7 O 24 ] 6− is an exceptionally redox‐active polycounterion showing metal‐centered redox processes [10–12] . One strategy to increase capacity is to blend POMs with redox‐active organic molecules to yield inorganic‐organic hybrid materials.…”

“…[9] Particularly, the heptamolybdate anion [Mo 7 O 24 ] 6À is an exceptionally redox-active polycounterion showing metal-centered redox processes. [10][11][12] One strategy to increase capacity is to blend POMs with redox-active organic molecules to yield inorganic-organic hybrid materials. para-Phenylenediamine (PPD) represents an excellent redox mediator through a two-electron oxidation-reduction reaction.…”