The synthesis, crystal structure, spectral characterization, photochemistry, electrochemical and thermal studies of the hexakis(butan-1-aminium) heptamolybdate(VI) tetrahydrate (1) are reported. Dissolution of a mixed mono-hepta compound (BuNH₃)₈[(Mo₇O₂₄)(MoO₄)]·3H₂O in water results in its transformation to the title compound viz., (BuNH₃)&#8326 [Mo₇O₂₄]·4H₂O 1 (BuNH₃ = butan-1-aminium). The structure of the title compound consists of two crystallographically unique [Mo₇O₂₄]⁶⁻ anions, twelve independent (BuNH₃)⁺ cations and eight unique lattice water molecules, all of which are interlinked with the aid of three varieties of Hbonding interactions. Solar irradiation of 1 results in the formation of a bis(μ2-oxo) bridged diheptamolybdateproduct. Electrochemical studies reveal the role of 1 in the photodimerization process. Thermal decomposition of 1 results in the formation of crystalline α-MoO₃.