Synthesis, Structure, and Photochemistry of an Organic Heptamolybdate‐Monomolybdate

Treatment of MoO 3 with butan‐1‐amine (BuNH 2 ) or pyrrolidine (PyrNH 2 ) results in the formation of (BuNH 3 ) 8 [(Mo 7 O 24 )(MoO 4 )] · 3H 2 O ( 1 ; BuNH 3 = butan‐1‐aminium) or (PyrNH 2 ) 6 [(Mo 7 O 24 ] · 2H 2 O ( 2 ; PyrNH 2 = pyrrolidinium), respectively. On irradiation with sunlight, compound 1 , which is an organic heptamolybdate [Mo 7 O 24 ] 6– that contains a cocrystallized monomolybdate [MoO 4 ] 2– in the same compound, is transformed to an oxido‐bridged diheptamolybdate (BuNH 3 ) 10 [(Mo 7 O 22 )(μ 2 ‐O) 2 (Mo 7 O 22 )] · 5.5H 2 O ( 1b ). The [Mo 7 O 24 ] 6– units in 1 and 2 are made up of edge‐sharing [MoO 6 ] octahedra, whereas the central unit in 1b is a bis(μ 2 ‐O)‐bridged heptamolybdate dimer. Hydrogen bonding among the lattice water molecules in 1 results in the formation of a water octamer, whereas hydrogen bonding between the lattice water molecules and [Mo 7 O 24 ] 6– in 2 results in the formation of a one‐dimensional water‐linked heptamolybdate chain. Supramolecular structures, photochemistry, and thermal properties of 1 , 1b , and 2 are reported. For comparison of photochemical behavior, two more polyoxomolybdates, (PrNH 3 ) 6 [Mo 7 O 24 ] · 3H 2 O ( 3 ; PrNH 3 = propan‐1‐aminium) and (PentNH 3 ) 6 [Mo 7 O 24 ] · 3H 2 O ( 4 ; PentNH 3 = pentan‐1‐aminium), were prepared and characterized.