--NR.sup.10 --, --CH.dbd.CH-- or --O--;n is an integer of 2 or 3;R.sup.1 and R.sup.2 each represents an unsubstituted alkyl group or a substituted alkyl group;R.sup.12 represents a substituted aryl group, wherein said aryl group is substituted by an acidic substituent;R.sup.10 and R.sup.11 each represents an unsubstituted alkyl group or a substituted alkyl group;X represents an anion; andm represe