sents a hydrocarbon structure connecting X+'s, provided that at least one pair of X+'s connected by A or B has a structure in which the X's connected are present in the same conjugated system, and that when two or more A's a represent, they may be the same or different, l represents 0 or 1, provided that when X is a sulfur atom, l represents 1, and that when X is an iodine atom, 1 represents 0, m