An Al-complex with salicylic acid derivatives as ligands (commercial product E-88 from Orient Chemical Industries) is a typical commercial charge-control agent (CCA). At present, E-88 is widely used for full color toners, since it is colorless. However, E-88 possesses a relatively low and broad decomposition range between 130 and 170° C. For this reason, an attempt has been made in the present study to improve the thermal stability by investigating a new polymorph that possesses a higher thermal stability. Trial was then made to grow crystals by recrystallization from solution in various solvents. Among these, dimethylsulfoxide gave a hexanuclear Al-complex (molecular weight: 3310) that exhibits an extraordinarily high decomposition temperature of 270° C. In addition, this compound is found to exhibit excellent charge-control performance. Furthermore, the temperature dependence of the electrical conductivity of E-88 has also been studied in connection with our previously proposed charge-control mechanism of CCAs.