ch other and X??? is a halogen ion or SCN???; wherein R1, R2, R3, and R4 are each independently an alkyl group having one or more carbon atoms, preferably 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms such as phenyl, or a methoxymethyl group and may be the same or different from each other and X??? is a halogen ion or SCN???.