Disclosed are compounds having the following formula: (I) wherein R is an alkane chain having between 8 and 20 carbon atoms, and A is one or more anions having a total charge of −；2； or R is a quaternary amine having the following formula: (1a) wherein Ra and Rb are each an alkane chain having between 8 and 20 carbon atoms, and A is one or more anions having a total charge of −；3.
