| abstract |
The trimer of the indole carboxylic acid ester is represented by general formula (1) (wherein, R is a 1-6C linear or branched alkyl group; n is an integer of 1-4; X<SP>a-</SP>is at least one kind of an anion selected from the group of mono- to tri-valent anions consisting of chloride ion, bromide ion, iodide ion, fluoride ion, nitrate ion, sulfate ion, bisulfate ion, phosphate ion, fluoroborate ion, perchlorate ion, thiocyanate ion, acetate ion, propionate ion, methanesulfonate ion, p-toluenesulfonate ion, trifluoroacetate ion and trifluoromethanesulfonate ion; (a) is a valence of the ion of X; and m is 0-0.5). |