Structural Variation in Polyoxomolybdate Hybrid Crystals Comprising Ionic-Liquid Surfactants

Abstract

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.

A Robust Framework Based on Polymeric Octamolybdate Anions and Copper(II) Complexes of Tetradentate N-donor Ligands

“…The [γ-Mo8O26] 4-anion consists of six octahedral {MoO6} and two five-coordinated {MoO5}, resulting in two {Mo4O15} rhomb-like tetramers linked to each other through edge sharing. Because of the presence of five-coordinated molybdenum centers, γ-octamolybdate anions can be organically derivatized with alcoxo groups [51,52], and tend to further condense in acidic conditions with analogous clusters, leading to polymeric chains based on the γ-Mo8O28 subunit. The connection usually takes place by sharing one or two corners with adjacent units that result in {Mo8O27}n and {Mo8O26}n like chains, respectively and less frequently via edge sharing.…”

Inorganic–Organic Hybrid Surfactant Crystals: Structural Aspects and Functions

“…A one-dimensional chain structure composed from Mo 8 and a sodium cation is formed (Figure 12b, upper). Different types of sodium ion-containing hybrid crystals have been obtained by using ionic liquid C n mim (n = 10, 12) surfactant cations (Figure 12a) [124]. Notably in these cases, two sodium ions as well as two C n mim cations are contained per one β-or γ-Mo 8 having a charge of 4´, different from the C 16 py-β-Mo 8 hybrid crystals.…”

“…Single-headed surfactants contain alkyltrimethylammonium ([CnH2n+1N(CH3)3] + (CnNC3), Figure 6a) [113,115,116,119,125,126,130,131] Figure 6b) [114,117], or alkylammonium derived from primary amine ([CnH2n+1NH3] + (CnNH3), Figure 6c) [123]. In addition, heterocyclic surfactants such as pyridinium ([C5H5N(CnH2n+1)] + (Cnpy), Figure 6e) [118,[120][121][122][127][128][129], pyridazinium ([C4H4N2(CnH2n+1)] + (Cnpda), Figure 6f) [128], and methylimidazolium ([(CnH2n+1)C3H3N2(CH3)] + (Cnmim), Figure 6g) [123,124] are employed. Double-headed surfactants employed are alkyldiammonium derived from diamine ([H3N(CH2)nNH3] 2+ (H3NCnNH3), Figure 6d) [132,133] or synthetic bolaamphiphiles having two charged heterocyclic moieties [134][135][136].…”

“…One option for the functionalized POM-surfactant crystals is to introduce other countercations such as proton or sodium into the crystal structures as well as surfactant cations. The crystals containing β-type Mo8 anions tend to crystallize with small countercations such as proton or sodium [120][121][122]124], and are promising candidates for the solid electrolyte for fuel-cell or sodium-ion batteries. The surfactant hybrid crystals containing small countercations are limited to the crystals consisting of β-Mo8, γ-Mo8, and V10 to date.…”

“…Electronic conductivities for hybrid crystals of C16py-W10 ( Figure 13) [127] and C16py-Mo4 [129] are in the range of 10 −6 to 10 −5 S cm −1 order. Although these values are much lower than the radical salts of POM containing an organic donor [8,9], POM-surfactant crystals with an appropriate combination of POMs and surfactants Sodium ion-containing hybrid crystals of Mo 8 can be synthesized in the presence of a sodium ion by using C n py or C n mim ( Figure 12) [120,121,124]. In cases where a C 16 py cation is employed, one β-Mo 8 anion having a charge of 4´is associated with three C 16 py surfactant cations and one sodium cation [120,121].…”