Patent ID: 7255779

Claim:
An indolecarboxylic ester trimer represented by the following general formula [1]: wherein R represents a straight or branched chain alkyl group having 1 to 6 carbon atoms; n represents an integer of 1 to 4; X a− represents at least one anion selected from the group consisting of anions having a valency of 1 to 3, said group comprising chloride ion, bromide ion, iodide ion, fluoride ion, nitrate ion, sulfate ion, hydrogen sulfate ion, phosphate ion, borofluoride ion, perchlorate ion, thiocyanate ion, acetate ion, propionate ion, methanesulfonate ion, p-toluenesulfonate ion, trifluoroacetate ion and trifluoromethanesulfonate ion; a represents an integer of 1 to 3 which represents the ionic valence number of X; and m represents a number of 0 to 0.5.