Comparative Study of Inorganic Cluster−Surfactant Arrays

Abstract

We have investigated inorganic cluster-surfactant materials to better understand the structural evolution of these phases as the surfactant:cluster ratio increases above 4:1 and the cluster charge increases beyond -4. Our studies suggest that both ordering of the surfactant molecules into bilayers as well as the cluster charge are the primary influences on the hybrid cluster-surfactant phase structure. However, cluster geometry, inclusion of solvent molecules, surfactant tail length, cation head size, etc. also influence the self-assembly of these materials. We present the synthesis, characterization, and single-crystal X-ray structure of [SiMo 12 O 40 ][C 16 H 33 N(CH 3 ) 3 ] 4 (monoclinic P2 1 /c, a ) 13.136(1) Å, b ) 20.139(2) Å, c ) 41.030(3) Å, β ) 93.443(1)°, and V ) 10834.7(17) Å 3 ) and the synthesis and characterization of a related phase that forms upon chemical reduction of the silicomolybdate anion. Structural and chemical comparisons are made between these two compounds, as well as other phases formed from polyoxometalates (with charges ranging from -3 to -16) and surfactants. The structure of [SiMo 12 O 40 ][C 16 H 33 N-(CH 3 ) 3 ] 4 is compared to the structures of other reported cluster-surfactant phases that also have a 1:4 cluster:surfactant ratio. Analyses of these phases provide some insight as to why it is thus far only this 1:4 ratio that provides crystals suitable for single-crystal diffraction studies and how the structure of the cluster-surfactant phases evolves as the surfactant/cluster ratio is increased.

Polyoxotungstate-Surfactant Layered Crystal toward Conductive Inorganic-Organic Hybrid

“…The crystal packing consisted of alternating W 10 inorganic layers and C 16 py organic layers with periodicity of 23.3 Å (Figure 1). The W 10 anions formed monolayers, while the hexadecyl chains of C 16 py interdigitated to form a bilayer structure, which is a typical structure for most POM-surfactant hybrid crystals [26][27][28][29][30][31][32]. All C-C bonds in the hexadecyl chains showed anti conformation except one C-C bond (C7-C8 The hydrophilic heads of C 16 py penetrated into the W 10 inorganic monolayers and isolated each W 10 anion ( Figure 2) in a similar way to that in the crystal of C 16 py-hexamolybdate (C 16 py-Mo 6 ) [31] or C 16 py-α-octamolybdate (C 16 py-α-Mo 8 ) [32].…”

“…POMs can add various physicochemical properties to the hybrids as inorganic components [12][13][14][15][16], while surfactants enable the control of layered structures as structure-directing organic components [17][18][19]. While there are many types of POM-surfactant hybrid [9][10][11][20][21][22][23][24][25], POM-surfactant single crystals are rare [26][27][28][29][30][31][32]. These POM-surfactant hybrids can allow fine tuning of the structures and functions, and are promising conducting materials as precedented inorganic-organic hybrid conductors [2,3].…”

Electronic and relativistic contributions to ion-pairing in polyoxometalate model systems

“…This is a departure from the typical behavior of most POM salts whose countercations are completely displaced by surfactants. 52 In the case of the Cs{M 6 }, the Cs can never be fully displaced by this rapid precipitation process, giving an indication of how many Cs-cations are associated per cluster for any solution concentration. Therefore, we can directly compare the Cs + /{M 6 } ratio for {Nb 6 } and {Ta 6 } at the same concentration to corroborate our observation by NMR that there is more Cs + associated to hexatantalate than hexaniobate in water.…”

A PGSE-NMR Study of Molecular Self-Diffusion in Lamellar Phases Doped with Polyoxometalates

“…[1][2][3][4][5][6] In this context, polyoxometalates, 7-9 thanks to their outstanding electronic properties, are inorganic building blocks that are becoming increasingly popular in soft-condensed matter studies. [10][11][12][13][14][15][16][17][18][19][20][21][22][23] Being negatively charged, they are most often associated to cationic surfactants, via ionic self-assembly processes. In a previous study, we formulated a hybrid system where the inorganic component is the [PW 12 O 40 ] 3-polyoxometalate (POM) anion ( fig.…”