prov:value
| - 1) when none of X1, X2 and X3 is SO3 H or COOH, then at least one 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 SO3 H or COOH, and at least two of X and Xo and the X1, X2 and X3 which are not SO3 H or COOH are independently fluoro, chloro, bromo or NO2, and (3) no more than two of X1, X2 and X3 are SO3 H or COO
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