A tetrapyrollic photosensitizer compound having at least one pendant —CH2CH2CON(CH2CON(CH2COOH)2)2 or —N(CH2COOH)2 group or esters thereof said tetrapyrollic compound being a chlorin, bacteriochlorin, porphyrin, pyropheophorbide, purpurinimide, or bacteriopurpurinimide. Desirably the compound has the formula: