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The rate constants for complexation of A-methyltetraphenylporphyrin by Cu(II), Zn(II), Co(II), Mn(II), and Ni(II) perchlorate salts in , -dimethylformamide were determined at several temperatures in order to investigate general features of porphyrin metalation reactions. All reactions obey a second-order rate law, first order in porphyrin and first order in metal ion. At 25 °C, the complexation rate constants (in M™1 s™1) are 289 ± 52 for Cu(II), 10.4 ± 0.8 for Zn(II), 0.68 ± 0.04 for Co(II), 0.010 ± 0.002 for Mn(II), and 0.0003 for Ni(II). Activation parameters for these reactions (AH* in units of kcal/mol and AS* in eu) are AH* = 16.9 ± 1.8 and AS* = 9.7 ± 6.0 for Cu(II), AH* = 14.2 ± 0.7 and AS* = -6.7 ± 2.6 for Zn(II), AH* = 20.4 ± 1.1 and AS* = 8.6 ± 3.6 for Co(II), AH* = 21.6 ± 0.5 and AS* = 4.5 ± 1.6 for Mn(II), and AH* = 21.4 ± 2.0 and AS* = -3.2 ± 5.8 for Ni(II). With the exception of the Mn(II) reaction, the order of the porphyrin metalation rate constants, Cu(II) > Zn(II) > Co(II) > Ni(II), coincides with the rates of solvent exchange of the metal ions. The Mn(II) complexation rate is slower than would be predicted from solvent-exchange rates. This anomaly has also been found for Mn(II) complexation of both tetra(p-sulfophenyl)porphyrin and tetrakis(4-A-methylpyridyl)porphyrin. The general trend supports a porphyrin metalation mechanism in which solvent dissociation from the metal ion is a rate-determining factor. The rates for complexation of A-methyltetraphenylporphyrin are faster than rates for planar porphyrins, indicating the importance of porphyrin deformation to the rate. The results support a dissociative interchange mechanism as a predominant path for both A-methyl and planar porphyrins.

Starburst dendrimers, spherical polymers constructed from methyl acrylate and ethylenediamine, were successfully used to covalently couple synthetic porphyrins to antibody molecules. The dendrimers, as linker molecules, have great potential for increasing the specific activity of radiolabeled antibodies for tumor therapy and diagnosis.

The monomeric pentaammineruthenium(II) complexes (NH3)5RuL2+, with L = pyridine, pyrazine, 4-phenylpyridine, 4,4'-bipyridine, 1,2-bis(4-pyridyl)ethylene, and the dimeric complexes [(NH3)5Ru]2L' 4+, with L' = pyrazine, 4,4'-bipyridine, and 1,2-bis(4-pyridyl)ethylene, have been synthesized and characterized. The visible absorption spectra of the complexes were studied to determine the relationship of the charge-transfer energies to electronic properties of the ligand and a reasonable molecular orbital scheme for the complexes was developed. The basicities of the pyrazine, 4,4'-bipyridine, and 1,2-bis(4-pyridyl)ethylene complexes were determined at 25°and an ionic strength of 0.05. The ligand pAfs are: for 4,4'-bipyridine, pKi = 3.2 and pK2 = 4.9; for l,2-bis(4pyridyl)ethylene, pXi = 4.4 and pK2 -5.9. The ruthenium complexes (NH3)5RuL2+ had pK's of 2.6 for pyrazine, 4.4 for 4,4'-bipyridine, and 5.0 for 1,2-bis(4-pyridyl)ethylene. Nuclear magnetic resonance spectra of the series of complexes are reported, showing a net positive charge on the ligands due to complexation. This study points to an interpretation of the increased ligand basicity for complexed pyrazine as the Ru(II) allowing for easier delocalization of the protonated species as compared to the alternative explanation based on an increase in electron density of the free nitrogen viaback bonding.

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