Synthesis, characterization, and tuning of the liquid crystal properties of ionic materials based on the cyclic polyoxothiometalate [{Mo4O4S4(H2O)3(OH)2}2(P8W48O184)]36−

Abstract

A series of compounds resulting from the ionic association of a nanoscopic inorganic cluster of formula [K₂Na_xLi_y{Mo₄O₄S₄(OH)₂(H₂O)₃}₂(H_zP₈W₄₈O₁₈₄)]^{(34−x−y−z)−}, 1, with several organic cations such as dimethyldioctadecylammonium DODA⁺, trimethylhexadecylammonium TMAC₁₆⁺, alkylmethylimidazoliums mimC_n⁺ (n = 12–20) and alkyl-dimethylimidazoliums dmimC_n⁺ (n = 12 and 16) was prepared and characterized in the solid state by FT-IR, EDX, Elemental analysis, TGA and solid state NMR. The solid state NMR experiments performed on ¹H, ¹³C and ³¹P nuclei evidenced the interactions between the cations and 1 as well as the organization of the alkyl chains of the cations within the solid. Polarized optical microscopy, DSC and SA-XRD experiments implicated mesomorphic phases for DODA⁺ and mimC_n⁺ salts of 1. The crystallographic parameters were determined and demonstrated that the inter-lamellar spacing could be controlled upon changing the length of the alkyl chain, a very interesting result if we consider the huge size of the inorganic cluster 1 and the simple nature of the cations.