Naphthylimido-Substituted Hexamolybdate:  Preparation, Crystal Structures, Solvent Effects, and Optical Properties of Three Polymorphs

[(n-C₄H₉)₄N]₂[Mo₆O₁₈(N-1-C₁₀H₆-2-CH₃)] (1) has been prepared by the reaction of 1-amino-2-methylnaphthalene hydrochloride with [(n-C₄H₉)₄N]₄[α-Mo₈O₂₆] in the presence of 1,3-dicyclohexylcarbodiimide. Three solvent-free crystalline phases are isolated from the mixed solvents of acetone and acetic ether. The X-ray single-crystal structures of the three phases have been determined, showing the packing and supramolecular assembly characters (pseudohigher symmetry, helical chains, and π−π stacking) by which the effect of solvent polarity and crystallization speed on polymorphism in organic−inorganic hybrids has been demonstrated.