Hybrid inorganic–organic crystals containing α- and β-type octamolybdates (α-Mo8 and β-Mo8) were successfully prepared by using hexadecylpyridinium (C16py). Although both hybrid crystals consisted of alternate stacking patterns of monolayers of Mo8 anions and interdigitated bilayers of C16py cations, the Mo8 inorganic monolayers had different packing patterns between the hybrid C16py–α-Mo8 and C16py–β-Mo8 crystals. Each α-Mo8 was isolated by the inserted C16py cations, while β-Mo8 formed one-dimensional chains together with sodium cations.

Polyoxomolybdate inorganic–organic hybrid crystals were synthesized by using long-tailed primary amine and ionic-liquid surfactants. Dodecylamine and 1-dodecyl-3-methylimidazolium bromide were employed for the syntheses. Both hybrid crystals contained a β-type octamolybdate (Mo8) anion and showed alternate stacking of Mo8 monolayers and interdigitated surfactant bilayers. The arrangement of Mo8 layers in the inorganic monolayers was different between the hybrid crystals because of the difference in the structures of the surfactant hydrophilic head.

An inoranic–organic hybrid crystal was synthesized by using polyoxomolybdate and hexadecylpyridinium surfactant. The unit cell was monoclinic having quite a long cell dimension (b = 75.0111(14) Å). The crystal structure was formed by alternative stacking of β-octamolybdate bilayers and interdigitated hexadecylpyridinium bilayers with layered periodicity of 3.75 nm, which is the largest value for polyoxometalate–surfactant hybrid crystals.

Polyoxomolybdate inorganic-organic hybrid crystals were synthesized with 1-decyl-3-methylimidazolium and 1-dodecyl-3-methylimidazolium as ionic-liquid surfactants. Both hybrid crystals possessed alternate stacking of surfactant layers and octamolybdate (Mo 8 ) monolayers, while the molecular structures of Mo 8 were different depending on the surfactants and solvents employed for crystallization. Each Mo 8 anion was connected by two sodium cations to form infinite one-dimensional chain. The surfactant chains in these crystals were arranged in a complicatedly bent manner, which will be induced by the weak C-H· ··O hydrogen bonds between the Mo 8 anions and ionic-liquid surfactants.

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