Examples of the alkyl group in the alkylsulfonate and the aryl group in the arylsulfonate include those listed above as examples of alkyl groups, substituted alkyl groups, aryl groups, and substitutedaryl groups.Two or more of these R.sub.11, to R.sub.14, R.sub.21 to R.sub.24, R.sub.31 to R.sub.34 and R.sub.41 to R.sub.44 groups in General Formula 1 may be bonded together to form a ring.