Labeled complex

A labeled complex for detecting a subject compound to be analyzed by optical means using near-infrared radiation which complex comprises a substance from a living organism and a labeling agent fixed onto the substance and is bonded to the subject compound to be analyzed, Wherein the labeling agent comprises a compound represented by the general formula (I), (II) or (III):

• ##STR98## wherein R.sub.1 through R.sub.7 are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, aryl group, aralkyl group, sulfonate group, amino group, styryl group, nitro group, hydroxyl group, carboxyl group, cyano group, or arylazo group;
• R.sub.1 through R.sub.7 may be bonded to each other to form a substituted or an unsubstituted condensed ring;
• R represents a divalent organic residue;
• and X.sub.1.sup..crclbar. represents an anion;
• ##STR99## wherein R.sub.8 through R.sub.14 are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, aryl group, aralkyl group, sulfonate group, amino group, styryl group, nitro group, hydroxyl group, carboxyl group, cyano group, or arylazo group;
• R.sub.8 through R.sub.14 may be bonded to each other to form a substituted or an unsubstituted condensed ring;
• and R.sub.A represents a divalent organic residue;
• ##STR100## wherein R.sub.15 through R.sub.21 are independently selected from the group consisting of hydrogen atom, halogen atom, alkyl group, aryl group, a substituted or an unsubstituted aralkyl group, a substituted or an unsubstituted amino group, a substituted or an unsubstituted styryl group, nitro group, sulfonate group, hydroxyl group, carboxyl group, cyano group, or arylazo group, R.sub.15 through R.sub.21 may or may not be bonded to each other to form a substituted or an unsubstituted condensed ring;
• R.sub.B represents a divalent organic residue;
• and X.sub.1.sup..crclbar. represents an anion.