In some embodiments of the fourth group of compounds of formula IE, R4, R5, and R6 are selected from H or a halogen such as Cl or F. In other embodiments of the fourth group of compounds of formula IE, at least one of R4, R5, or R6 is a F whereas in other embodiments of the fourth group of compounds of formula IE, R4, R5, and R6 are all H.