Influence of pendant arms bearing ligating groups on the structure of bismuth porphyrins: Implications for labeling immunoglobulins used in medical applications

The synthesis of two picket bismuth(III) porphyrins is reported, and their crystal structures are compared. The influence of the nature of the pickets, as well as their number, is discussed in terms of stability, kinetics of metalation, structure, and distortion of the porphyrin. Unexpectedly, the results indicate that the coordination sphere of bismuth is not affected by different types of distortion nor is the stability of the complex. For both types of complexes, the X-ray crystallography revealed that a single arm is actually in direct interaction with the bismuth cation, thereby allowing further functionalization on the porphyrin core as the linkage with immunoglobulins or anti-rabbit antibodies (both noted IgG), which have been used in diagnostic or therapeutic applications.