at:(1) when none of X1, X2 and X3 is in a water solubilizing group, then at least one of Y and Yo on each porphyrin ring is other than H, (2) when Y and Yo are both H, at least one but not more than two of X1, X2 and X3 is water solubilizing group and at least two of X, Xo, X1, X2 and X3 is a non-water solubilizing electronegative group, or the water soluble salts thereof in which said water solub