Photoirradiation into the LMCT band (lambda(max): 362 nm) of self-assembled amphiphilic tetraphenylporphyrinato-iron(III) (lipidporphyrinato-iron(III)) chloride with hyaluronic acid leads to reduction of the central ferric ion in saline solution (pH 7.4, 25 degrees C); the obtained lipidporphyrinato-iron(II) can reversibly bind and release dioxygen.