Polyoxomolybdate–Surfactant Hybrid Layered Crystal with Unusually Long Periodicity

Abstract

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.

Inorganic–Organic Hybrid Surfactant Crystals: Structural Aspects and Functions

“…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].…”

“…The layered structure of POM-surfactant crystals comprises alternate stacking of POM monolayers and surfactant bilayers, as shown in Figure 8c. A few crystals possess the bilayer packing manner of POM anions [119,121]. The inorganic POM layer can be considered as an atomically regular two-dimensional POM array, and the molecular arrangement of POM anion is controllable by changing the structures of surfactant hydrophilic head.…”

Structural Variation in Polyoxomolybdate Hybrid Crystals Comprising Ionic-Liquid Surfactants

“…The single crystal X-ray structure analysis combined with the elemental analysis revealed the formula of C 10 im-Na-Mo 8 [27,28]. The space between the β-Mo 8 -Na + chains were filled by imidazole rings of C 10 im, which were located in the vicinity of Na + cations.…”

“…The C 10 im cations had complicatedly bent conformation in their chain structure. The presence of more than two gauche C-C bonds per one alkyl chain was rarely observed for polyoxometalate-surfactant hybrid crystals [21][22][23][24][25][26][27][28][29][30]. The C-C bonds in the butyl groups had anti conformation.…”

“…Polyoxometalate anions having physicochemical functions such as redox, catalytic or conductive properties [7][8][9][10][11][12] have been successfully organized by structure-directing surfactants to construct inorganic-organic hybrids [13][14][15][16][17][18][19][20] and layered crystals [21][22][23][24][25][26][27][28][29][30]. These polyoxometalate-surfactant hybrids allow flexible selection of the ionic components including ionic liquid [31][32][33][34][35][36], which leads to precise engineering of the structure and function.…”