Mesophases and Ionic Conductivities of Simple Organic Salts of M(m-Iodobenzoate) (M = Li super(+), Na super(+), K super(+), Rb super(+), and Cs super(+))

Simple organic salts such as (Li super(+))(m-IBA) (1), (Na super(+))(m-IBA) (2), (K super(+))(m-IBA) (3), (Rb super(+))(m-IBA) (4), and (Cs super(+))(m-IBA) (5) (m-IBA = m-iodobenzoate) were shown to form a mesophase before crystal melting or decomposition. The crystals were obtained in the hydrated form, e.g., 1.(H sub(2)O), 2.(H sub(2)O), 3.0.5(H sub(2)O), 4.(H sub(2)O), and 5.(H sub(2)O); they were then converted into dehydrated forms by increasing the temperature to similar to 450 K. Optically anisotropic-layered mesophases were observed in unhydrated crystals 2, 3, 4, and 5, whereas an optically isotropic mesophase (e.g., rotator phase) was found for crystal 1. The single-crystal X-ray structural analysis of the hydrated crystals revealed an inorganic-organic alternate layer structure, which is consistent with the average molecular orientation in the layered mesophase. The m-IBA anions formed a pi -stacking columnar structure in the hydrated crystals, while one- or two-dimensional M super(+) similar to O networks were observed in the inorganic layers. Our results showed that the M super(+) similar to O interactions and their connectivity are strongly influenced by the size of the cations. The reconstruction of the M super(+) similar to O networks by removing H sub(2)O molecules was crucial for the formation of the mesophases. A strong response of both the real and imaginary parts of the dielectric constant was observed around the solid-mesophase phase-transition temperatures of crystals 1-5, with the ionic conductions playing a critical role.