Crystal structure and ionic conductivity of the soft solid crystal: isoquinoline 3 •(LiCl) 2

A soft solid crystal composed of isoquinoline (IQ) and LiCl was prepared based on the concept of Pearson’s hard-soft acid-base (HSAB) theory. Single-crystal X-ray diffraction best described the isoquinoline3•(LiCl)2 as consisting of molecular Li4Cl4(isoquinoline)6 units, where the LiCl cluster is an array of edge-fused Li2Cl2 rhombs. Electrochemical impedance measurements on pressed pellets showed that conductivity occurs mainly through the bulk via a hopping mechanism, with a calculated activation energy of Ea = 67 kJ/mol. The high value of the activation energy was due to Li4Cl4 clusters that were well separated by intervening IQ ligands in the crystal structure, requiring large hops for ions to migrate through the lattice.