We first synthesized and characterized a monomer ruthenium complex of hypocrellin B (HB) by chelation with Ru-(bpy)(2)Cl-2 (in which bpy = 2,2'-bipyridine). It possesses the photosensitizing properties and can be applied in photodynamic therapy (PDT). The chemiluminescence assays indicated that the photodamage ability of the complex is stronger than that of HB. (c) 2005 Elsevier Ltd. All rights reserved.