the present invention discloses novel sulfenate derivatives and their bioconjugates for phototherapy of tumors and other lesions . the sulfenates of the present invention are designed to absorb low - energy ultraviolet , visible , or near - infrared region of the electromagnetic spectrum . the phototherapeutic effect is caused by direct interaction of free radicals , the reactive intermediate produced upon photofragmentation of the sulfenate moiety , with the tissue of interest .